It is important to keep media-mixing areas free of weeds to avoid the introduction of weed seeds into container media. |
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Many weeds that are difficult to control after the crop is planted can be eliminated from a field prior to planting by mechanical or chemical means. Repeated cultivation throughout the growing season will exhaust weed food reserves and result in weed death. This system avoids the use of chemicals but is expensive in terms of fuel and labor, may break down soil structure, and may spread, rather than kill, some tough to control perennial weeds.
Treatment with the chemicals listed below can be less expensive and will maintain soil structure while killing perennial weeds. The postemergence herbicides are most effective when applied from midsummer to early fall because they should be applied to mature but actively growing weeds. Many perennial weeds do not grow and mature early enough in the spring to allow time for application and translocation of the herbicide prior to the time of planting. Do not cultivate soil before applying a translocated herbicide. Cultivation breaks up a plant and its roots and spreads the pieces deeper and over a wider area. Each piece is capable of forming a new plant. These pieces do not all start growing at the same time and it is very difficult to kill all of them. If the plant is intact when treated, the chemical will move throughout the plant and kill all parts of it.
After allowing sufficient time for a systemic herbicide (e.g., Roundup Pro, Garlon) to translocate throughout the weeds, the field can be plowed and replanted without fear of herbicide residue. A cover crop of sudan-sorghum in the summer or ryegrass in the fall will limit weed regrowth, build soil organic matter and structure, and prevent erosion.
Roundup Pro applied at 1 to 3 lb ai/A is the safest, most effective broad spectrum herbicide available for eliminating weeds from a field prior to planting. Use the low rate for low-density, especially sensitive weeds (grasses) and higher rates for high-density, hard-to-control weeds (e.g., briars, poison ivy, milkweed, Canada thistle, nutsedge).
Garlon applied at 1 to 3 lb ai/A provides excellent control of herbaceous broadleaved weeds and woody weeds such as poison ivy, briars, and brush. It does not control grasses. For broad spectrum control, use Roundup at 1 to 2 lb ai/A plus Garlon at 1 to 2 lb ai/A.
Dichlobenil (Casoron, Barrier, Dyclomec, Norosac) applied in a granular form at 6 to 8 lb ai/A in late fall will suppress or kill quackgrass, mugwort, dandelion, bindweed. Canada thistle, and some other perennial weeds. Do not plant sensitive plants (fir, hemlock, pine, spruce) the following spring if the 8 lb rate is used.
Kerb applied in late fall or early winter at 1 to 2 lb ai/A is especially effective for controlling perennial grasses such as quackgrass. It provides better control of the fine fescues than any other herbicide.
The effectiveness of a weed control program in a landscape or cropping system can be reduced if weeds around the managed area are allowed to grow and produce seeds. The seeds from these weeds will blow into the managed areas and make preventive efforts more difficult. Weeds should be controlled in surrounding unused areas, fields, roadways, drainage ditches, and in and around container-grown nursery stock.
Finale, Reward, or Scythe can be used to control annual weeds in these areas.
Roundup Pro should be used if perennial weeds are present.
Rodeo provides systemic control of weeds in and around ponds or drainage ditches. Reward may be used on the edge of drainage ditches or ponds only if there is no outflow of water from the nursery property.
Princep and Factor, Pendulum, or Surflan should be included with the postemergence herbicide chosen, to prevent regrowth of weeds.
2,4-D, Garlon, and Stinger are herbicides that selectively kill broadleaved weeds and should be applied to turf areas around the crop.
The herbicides listed in Table 4 can be combined to kill existing weeds and provide residual control following application. Choose one herbicide from each of the three categories. Mix the amount of herbicide indicated in 1 gallon of water and apply it uniformly over 500 square feet. Weed foliage and bare soil should be lightly, but uniformly covered. Use a marker dye when spot treating to make areas receiving an overapplication clearly visible.
| Table 4. Herbicide combinations for weed control in noncrop areas. | |||
|---|---|---|---|
| Category | Amount per acre | Amount per gallon (500 sq ft) | |
| (english) | (metric) | ||
| 1. Postemergence herbicides | |||
| Finale 1SC | 3-6 qt | 1.1-2.2 fl oz | 33-66 ml |
| Reward | 1-2 qt | 0.4-0.75 fl oz | 12-22 ml |
| Roundup Pro | 1-4 qt | 0.3-1.5 fl oz | 9-45 ml |
| Scythe | 3-27 gal | 6.5-13 fl oz | 190-380 ml |
| 2. Preemergence herbicides best on broadleaves | |||
| Gallery | 0.66-1.33 lb | 0.13-0.25 oz | 4-8 gm |
| Princep 4L | 2-4 qt | 0.8-1.5 fl oz | 23-45 ml |
| Princep 90DF | 2.2-4.4 lb | 0.4-0.75 oz | 12-23 gm |
| 3. Preemergence herbicides best on grasses | |||
| Factor 65WG | 1.0-2.3 lb | 0.18-0.41 oz | 5.4-12 gm |
| Pendulum 3.3EC | 2.4-4.8 qt | 0.9-1.8 fl oz | 27-54 ml |
| Pendulum 60WDG | 3.3-6.6 lb | 0.6-1.2 oz | 18-36 gm |
| Pennant | 2-4 pt | 0.4-0.75 fl oz | 12-22 ml |
| Surflan | 2-4 qt | 0.75-1.5 fl oz | 24-44 ml |
Extreme caution must be used when controlling weeds in seedbeds because the crop itself is very sensitive to mechanical and chemical injury in the seedling stage of development. Providing broadleaf or preemergence weed control in seedbeds of plants other than conifers is still very difficult. Surflan has proven to be especially damaging when applied within 1 or 2 years of germination of some species. Special cultivators and weed brushes developed for use in narrow-row spaced crops can be used in seedbeds that are grown in rows. Though it is an extremely labor-intensive job, hand-pulling of weeds is a common practice in almost all seedling production nurseries.
It is best to limit early weed growth by steam pasteurizing or fumigating seedbeds prior to planting.
Heating the soil to 160 degrees F with steam for 30 minutes will kill most weed seeds and stolons. Steaming at 180 degrees F eliminates most other harmful organisms such as insects, diseases, and nematodes. Steam pasteurization of the soil is economical when high-value plants are grown in a limited area. Portable steam generators can be used for bed preparation.
Fumigants produce results similar to pasteurization if they are properly applied. There are specific instructions for use with respect to covering or sealing for each of the fumigants plus a specific waiting period prior to planting. For a list of fumigants, see page 25.
Special cultivators and weed brushes developed for use in narrow-row spaced crops can be used in seedbeds that are grown in rows. Equipment operators must be especially careful not to cultivate too deeply or too close to the seedlings to avoid extensive damage to the crop. The only nonchemical way to remove weeds from broadcast seeded beds is by handpulling.
Fusilade II and Vantage provide excellent postemergence control of grasses in seedbeds of conifers and deciduous ornamentals. All of the grasses should be growing from seed, so as little as 0.25 lb ai/A of Fusilade II or Vantage will control them at the 4- to 6-inch stage. Higher rates (0.25 to 0.50 lb ai/A) will be needed to control high-density, taller weeds.
Goal provides very good preemergence control and limited postemergence control of broadleaved weeds and grasses in conifer beds. It will severely injure seedlings of broadleaved plants. Apply 0.25 to 1 lb ai/A after seeding but prior to conifer germination. For postemergence control. apply 0.25 to 0.59 lb ai/A after seedlings are at least 5 weeks old. Try to make the first application before emergence of the conifers. If no preemergence application is made, many weeds will develop that are too large to be controlled by the postemergence application. Also, not all of the conifer seeds germinate at the same time, so some seedlings may still be at a sensitive stage 5 weeks after the first seedlings emerge.
Ronstar is labeled for use on pine seedbeds at 2 to 4 lb ai/A. Apply to seedlings at least 4 weeks old. Ronstar will severely injure emerging or small broadleaved plants.
If the value of the crop is high enough, the soil can be steam pasteurized or fumigated as described in the previous section. Weeds can be controlled with repeated cultivations. As with seedbeds, extreme caution must be used so that the small plants are not torn out of the ground or damaged. One or a combination of the following herbicides can be used to control weeds in liner beds. Alternating an application of a preemergence herbicide with cultivation can reduce the amount of herbicide used and the frequency of cultivation.
Devrinol should be applied at 4 to 6 lb ai/A between late fall or early spring. If applied in warm weather, Devrinol must immediately be incorporated with 1 to 2 inches of water or cultivation. Apply to newly planted stock after the soil has been settled by the first irrigation or rainfall.
Envoy applied at 0.1 to 0.25 lb ai/A will provide postemergence control of annual and perennial grasses.
Fusilade II applied at 0.125 to 0.50 lb ai/A will provide postemergence control of annual and perennial grasses.
Goal applied at 0.25 to 1 lb ai/A provides preemergence and limited postemergence weed control in conifers only. Apply before weed seedlings reach 4 inches in height. Application around small field-grown deciduous liners may result in severe injury. Do not mulch after applying Goal.
Kerb applied at 2 lb ai/A is effective against winter annual grasses, perennial grasses, and some broadleaved weeds. Apply over plants established at least one full growing season.
Pennant should be applied at 2 to 3 lb ai/A at least 10 days after transplanting to control annual grasses, nutsedge, and some broadleaved weeds. Use the 3 lb rate to control nutsedge. Liners should be well rooted before use. Irrigate after application to activate the herbicide and rinse the residue from the foliage.
Regal O-O should be applied at 3 lb ai/A for control of many annual grasses and broadleaved weeds. Application around small field-grown deciduous liners may result in severe injury. Do not mulch after application.
Ronstar should be applied at 3 lb ai/A for control of many annual grasses and broadleaved weeds. Application around small field-grown deciduous liners may result in severe injury. Do not mulch after applying Ronstar. The wettable powder formulation should not be applied during or within the 4 weeks following budbreak.
Treflan 4E is a preplant treatment applied at 1 lb ai/A for all woody plants. It is not effective in soils high in organic matter.
Vantage applied at 0.125 to 0.50 lb ai/A will provide postemergence control of annual and perennial grasses.
It is important to eliminate all weeds, especially perennials, prior to planting. If planting is delayed following elimination of weeds, additional weeds may germinate. In fields to be planted with a closely spaced crop like shrubs, weed seedlings should be killed with cultivation or an application of a postemergence herbicide several days prior to planting. In fields to be planted with trees spaced at least 5 feet apart, the postemergence herbicide can be combined with the preemergence application made following planting.
Following planting, cultivation, preemergence herbicides, or a combination of the two methods can be used to control weeds. Cultivation must be done very carefully before weeds get too large, to avoid pulling the newly planted stock out of the ground. Specially designed rotary cultivators with retractor arms can be used to control weeds in tree rows.
Hand weeding and hoeing are often necessary to clean up weeds that have escaped or are the most difficult weeds to control in an area.
With at least 5 feet between tree rows, a cover crop can be planted that will minimize the risk of erosion and pesticide or fertilizer runoff. If it is wide enough, equipment can be operated on it after rain without damaging the soil structure. It also continuously adds organic matter to the soil during the crop cycle.
Newly transplanted ornamentals have limited root systems and will be under stress. Several herbicides that can be safely used on established plants may injure those same plants if applied at the time of transplanting. The following herbicides can be safely applied to labeled newly transplanted stock, with the restrictions noted. For broad spectrum weed control, combine an herbicide that is best on broadleaved weeds with one that is best on grasses or use one of the premixed combinations.
Atrazine should be applied at 2 to 4 lb ai/A only to conifers listed on the label soon after transplanting in fall or early spring.
Gallery should be applied at 0.25 to 0.75 lb ai/A. Delay application to new transplants until the soil is settled by packing or irrigation and no cracks are present.
Goal should be applied at 0.25 to 1 lb ai/A before budbreak or after the foliage has had time to harden off. It can be applied immediately after transplanting, provided budbreak has not occurred. Goal is safe for use around most conifers and also around trees with no foliage within 3 feet of the soil surface.
Ronstar can be applied at 2 to 4 lb ai/A immediately after transplanting. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
Devrinol can be applied at 3 to 6 lb ai/A after the soil is settled by 1 inch of rain or irrigation. If applied in warm weather, Devrinol must be immediately incorporated with water or cultivation. In landscape plantings, apply Devrinol and cover it with an organic mulch for best results.
Factor (Barricade, Endurance, RegalKade G) should be applied at 1 to 1.5 lb ai/A after the soil has been allowed to settle around new transplants.
Lasso can be applied at 4 lb ai/A immediately after transplanting.
Pendulum can be applied at 3 lb ai/A after the soil is settled by 1 inch of rain or irrigation. Do not apply it over tender new growth.
Pennant should be applied at 2 to 3 lb ai/A at least 10 days after transplanting.
Surflan should be applied at 2 lb ai/A, but should not be applied until 4 weeks after planting. Do not apply on newly transplanted hemlock or Douglas fir.
Treflan 4E should be applied at 1 to 2 lb ai/A prior to planting. Incorporate to a depth of 2 inches with a rotovator immediately after application. Effectiveness is increased if shallow (1.5 to 2 inches) cultivation follows application within 2 to 3 weeks.
XL 2G should be applied at 4 to 6 lb ai/A, but application to new transplants should be delayed until the soil is settled by packing or irrigation and no cracks are present. Use XL 2G as a granular form of Surflan.
OH2 can be applied at 3 lb ai/A immediately after planting. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
RegalStar II can be applied at 2.4 lb ai/A after the soil has settled around new transplants. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it.
Regal O-O can be applied at 3 lb ai/A immediately after transplanting. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
Rout can be applied at 3 lb ai/A after the soil is settled by 1 inch of rain or irrigation. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
Snapshot TG can be applied at 1.5 to 3 lb ai/A to new transplants after the soil is settled by packing or irrigation and no cracks are present. Snapshot TG contains a broadleaf and a grass herbicide for broad-spectrum control.
To control weeds throughout the year, herbicides should be applied in the spring, summer, and/or fall as needed. Spring applications of preemergence herbicides should be made prior to weed seed germination. In untreated soil, some weeds start germinating soon after the soil thaws. In soil that received an herbicide application the previous fall, germination can be delayed for up to 8 weeks following thaw. A low rate of postemergence herbicide may be included with early spring applications made before budbreak to kill cool season weeds. Though Roundup Pro will work, it will not provide good control of perennial weeds when applied at this time. One of the contact herbicides will work just as well.
Fall applications are particularly desirable from two standpoints: labor for applications is usually more available in the late fall, and fall applications prevent weed infestations during the peak digging season in the spring. Winter annuals and the perennial weeds that germinate in September, October, and early spring and crabgrass that germinates in early May can thoroughly infest fields before labor is available for the spring cleanup. While early spring applications of herbicides could prevent most of these problems, most growers experience difficulty in getting the job done properly at this time. Herbicides that can be applied in the fall or winter include atrazine, dichlobenil (Casoron, Barrier, Dyclomec, Norosac), Devrinol, Factor, Gallery, Kerb, Princep, Pendulum, and Surflan.
After herbicides applied in the fall or winter are no longer effective in suppressing weed growth, clean cultivate the soil and make a spring or summer application with one of the following herbicides alone or in one of the combinations recommended on page 13. The combinations remain effective longer and provide a wider spectrum of weed control than a single chemical. More than one application probably will be needed to control weed growth throughout the summer. If a fall cover crop is to be planted, avoid the application of an herbicide that will remain effective past mid-August. Do not use the same preemergence herbicides for both applications in one year. Alternate products so resistant weed populations do not build up. For broad spectrum weed control, combine an herbicide that is best on broadleaved weeds with one that is best on grasses, or use one of the premixed combinations.
Atrazine should be applied at 2 to 4 lb ai/A between fall and early spring while trees are dormant or soon after transplanting. Apply before weeds are 1.5 inches tall.
Casoron, Barrier, Dyclomec, or Norosac should be applied at 6 to 8 lb ai/A only on established plants of the woody ornamentals listed on the label for control of perennial and annual broad-leaved weeds and grasses. Hemlock, fir, newly planted spruce, viburnums, and certain hollies are not tolerant. Preemergence control does not last past late spring.
Gallery applied at 0.5 to 1.0 lb ai/A provides control of many broadleaved weeds. Apply in late summer to early fall, in early spring prior to germination of target weeds, or immediately after cultivation. For best control, combine Gallery with one of the herbicides that is best on grasses.
Goal should be applied at 0.5 to 1 lb ai/A to labeled conifers prior to budbreak or after the foliage has had time to harden off. It is especially useful for late spring applications because it will kill weed seedlings up to 4 inches tall.
Princep should be applied at 1 to 4 lb ai/A at any time of the year to control most broadleaved weeds and some grasses. It can be applied alone but works best if combined with an herbicide that is most effective on grasses. The exact rate used will depend on prior Princep applications (the maximum rate is 4 lb ai/A Princep per year), whether it is being used in combination with another herbicide, and the texture of the soil. Higher rates must be used in heavy clay soils than in light sandy soils.
Ronstar should be applied at 2 to 4 lb ai/A to newly transplanted or established plants for control of annual broadleaved weeds and grasses. Do not mulch after application. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
Betasan, Lescosan, or Bensumec 4 LF should be applied at 12.5 lb ai/A to control crabgrass and annual bluegrass in established plantings. Late winter application is preferable.
Devrinol should be applied at 4 to 6 lb ai/A in the fall or winter to control weed growth until the following summer.
Eptam should be applied at 5 lb ai/A around established plants after growth starts in the spring. Eptam's use is limited by the fact that it must be incorporated to a depth of 2 to 6 inches immediately after application. Properly incorporated, it will control nutsedge, quackgrass, and mugwort.
Factor (Barricade, Endurance, RegalKade G) can be applied to established plants at 0.65 to 1.5 lb ai/A to control many annual grasses and some broadleaved weeds.
Kerb applied at 1 to 2 lb ai/A provides excellent control of a variety of grasses, including quackgrass and winter annuals. This preemergence herbicide provides postemergence control of many perennial grasses. Apply with Princep at 1 to 2 lb ai/A on labeled species for broad spectrum weed control. Kerb is best applied in the fall before the soil freezes. When applied alone, it will not control annual weeds invading in May or June.
Lasso should be applied at 4 lb ai/A to control annual grasses and certain broadleaved weeds. To control nutsedge, apply in the fall or early spring prior to emergence.
Pendulum should be applied at 2 to 4 lb ai/A to control annual grasses and some broadleaved weeds. Do not use it over tender new growth.
Pennant should be applied at 2 to 4 lb ai/A to established labeled species. To control nutsedge, apply in early spring prior to emergence.
Predict should be applied at 2.4 lb ai/A in the fall or spring to control some grasses and a few broadleaved weeds in nursery plantings. To avoid plant injury, apply as a directed spray, avoiding contact with foliage, and do not apply until the fall following the first full season after transplanting.
Surflan should be applied at 2 to 4 lb ai/A to established labeled species to control annual grasses and some broadleaved weeds.
XL 2G should be applied at 4 to 6 lb ai/A, but application to new transplants should be delayed until the soil has been settled by packing or irrigation and no cracks are present. Use XL 2G as a granular form of Surflan.
OH2 should be applied at 3 lb ai/A to control a wide spectrum of annual broadleaved weeds and grasses. Do not mulch after application. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
Regal O-O should be applied at 3 lb ai/A to control many annual grasses and broadleaved weeds. Do not mulch after application. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
RegalStar II should be applied at 2.4 lb ai/A for control of annual grasses and broadleaved weeds. It is especially effective on crabgrass, goosegrass, and chickweed. Do not mulch after application. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Application can be made to actively growing or dormant ornamentals.
Rout should be applied at 3 lb ai/A in the fall or spring to control a broad spectrum of annual broadleaved weeds and grasses. Do not mulch after application. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Do not apply to deciduous plants less than 12 inches tall.
Snapshot TG applied at 2.5 to 5 lb ai/A will control many broadleaf and annual grass weeds in established labeled plantings.
The postemergence control of annual weeds should be minimized by using one or more of the preemergence herbicides listed in the preceding section. However, with the following exceptions, preemergence herbicides will not control weeds that have started to grow. Atrazine, Casoron, Kerb, and Princep will kill weed seedlings in the early stages of growth, and Goal will kill weeds up to 4 inches tall. Atrazine is currently labeled for use in conifer plantings only.
Since they die at the end of each growing season, annual weeds may be successfully controlled by cultivation or mowing. It is important to control them before they mature and set seed.
Postemergence herbicides can be used in certain situations in the nursery and landscape to eliminate annual and perennial weeds. Application of nonselective postemergence herbicides to established ornamentals entails the risk of plant injury. Perennial weeds should be eliminated prior to planting. Care should be taken not to reintroduce them by planting weed-infested stock.
Finale will kill actively growing annual weeds and burn the above-ground parts of perennial weeds. Repeat applications will be needed to control weeds emerging from underground parts or seeds.
Envoy will kill actively growing annual and perennial grasses. It can be applied over the top of most ornamentals.
Fusilade II will kill actively growing annual and perennial grasses. Read the label to determine which plants can be sprayed over the top and which should receive a directed spray.
Garlon will kill tough-to-control broadleaved weeds and woody weeds such as briars, Virginia creeper, and poison ivy. Garlon is labeled for use in conifer plantings and noncrop areas.
Manage will control yellow nutsedge and horsetail (Equisetum) when applied at 0.031 to 0.062 lb ai/A. Applications should not contact leaves of desirable plants since foliar injury, discoloration, or death may result. Allow 3 months after transplanting before applying this product.
Reward is a nonselective contact material that will control weeds both in and out of water. It is labeled for use in aquatic areas.
Roundup Pro should be applied when weeds are actively growing and ready to flower. Most broadleaved perennials are best controlled in late summer or early fall.
Vantage will kill actively growing annual and perennial grasses. It can be sprayed over the top of all labeled species.
These herbicides can be applied as directed sprays, spot treatments, or with wick applicators. A directed spray involves applying the herbicide so that it hits the weeds without contacting the foliage of the ornamentals. This type of application is most commonly used in plantings of large shrubs or trees. Spot treatments are used to eliminate pockets of weeds scattered throughout a planting. Wick applicators give the most control and allow exact placement of the herbicide on the weeds. There is no chance of drift. This type of applicator is especially useful in situations where weeds are growing above low-growing ornamentals such as ground covers.
Once an area has been cleared of weeds, measures should be taken to prevent immediate regrowth. Apply a mulch or a preemergence herbicide. Otherwise the area will have to be treated again with the postemergence herbicides two or three times during the growing season. To kill existing weeds and prevent emergence of others, apply a preemergence and postemergence herbicide in combination.
As in field nursery and landscape plantings, nurserymen growing plants in containers should have a weed control program. This means planning how to control weeds in the crop before it is planted. As mentioned in the introduction, the program has three parts:
|
It is important to keep media-mixing areas free of weeds to avoid the introduction of weed seeds into container media. |
|---|
Kill all herbaceous and woody perennial weeds in the proposed growing area. Roundup Pro at 2 to 4 qt per acre will kill most weeds. If especially difficult to control broadleaved or woody weeds are present, add 2,4-D, dicamba, or Garlon at 2 qt per acre to Roundup Pro. Applications made from early summer to early fall will be more effective than early spring applications.
For best results, remove 4 inches of topsoil from the site. Lay down a layer of geotextile and cover it with 2 to 4 inches of gravel or shale. This will stabilize the area for the operation of equipment, improve drainage, and minimize future weed problems.
After plants are in the area, eliminate all weeds that grow in and around the production area with Roundup Pro, Finale, Reward, or Scythe before seedhead development to limit the amount of seed that blows into the containers. The rate of application will depend on the type and size of weeds to be controlled.
For preemergence weed control in roadways, along property borders, and around structures; apply Princep plus Surflan or Pendulum at 2 to 4 qt per acre of each.
Start with a potting medium that is free of weeds. It should not contain parts of perennial weeds, and there should be few weed seeds in it. Generally, components such as peat, perlite, and vermiculite are weed-free. Composted products, such as bark or yard waste, will contain some weed seeds, and soil will contain many seeds. If weed-free ingredients are not used, pasteurization or fumigation of the container mix prior to planting will limit the extent of future weed problems.
Protect the components or the prepared medium from contamination with weeds or seeds while it is being stored prior to use. It can be stored indoors or covered with plastic. This will also prevent the leaching of any nutrients that may have been added to the medium.
Preemergence herbicides are commonly used in container production because the alternative, hand weeding, is extremely expensive. Container media provide an ideal environment for weeds, and the frequent irrigations and high organic matter content of the media reduce the length of time herbicides are effective. Three to four applications of herbicide may be required per year for adequate weed control, depending on the chemicals used, the rate, and the length of the growing season.
The first herbicide application should be made right after potting or uncovering overwintering structures in the early spring. Most chemicals require that the medium be firmly settled around roots by irrigation prior to application. This is especially critical for potted bare-root liners. An irrigation (1/2 to 1 inch) after application will wash the herbicide off the foliage of the ornamentals and move the chemical into the medium. If weed seedlings are present at the time of application, hand weed the area before applying the herbicide and follow up with a second hand weeding 7 to 10 days later to ensure elimination of previously germinated seedlings.
The second application should be made 6 to 8 weeks after the first. A third application may be needed during the growing season. The last application should be made 2 to 6 weeks prior to placing the plants in their overwintering structures. Again, hand weed prior to application. This final application is needed to control winter annuals that can grow in polyhouses anytime the weather warms up during the winter.
No preemergence products are labeled for use in covered houses.
Do not use the same preemergence herbicides for all applications in one year. Alternate products so resistant weed populations do not build up. Rout and OH2 are similar and should not be alternated with each other.
Container growers may have many plants that are not on the labels of any of the herbicides listed. Some products like Gallery, Snapshot TG, and Surflan allow growers to use these products on plants not found on the label, but the grower must assume all risk of injury to the plants.
Preemergence herbicides for use in container grown ornamentals that are best on broadleaved weeds include Gallery, Goal, Regal O-O, RegalStar, and Ronstar.
Preemergence herbicides for use in container grown ornamentals that are best on grasses include Devrinol, Factor, Pendulum, Pennant, RegalKade, Surflan (XL), and Treflan.
Premixed granular combinations of broadleaved and grass herbicides include OH2 (Goal + Pendulum), Regal O-O (Goal + Ronstar), RegalStar II (Ronstar + Factor + nitroform fertilizer), Rout (Goal + Surflan), and Snapshot T/G (Gallery + Treflan).
Always apply granular herbicides to dry foliage. Avoid using them on foliage that retains the granules, (e.g. Yucca).
Devrinol is effective at 4 to 6 lb ai/A. Irrigation immediately following application is essential for optimum control. Repeat applications every 10 to 12 weeks.
Factor (Barricade, Endurance, RegalKade G) may be applied to newly transplanted and established container stock at 0.65 to 1.5 lb ai/A as a broadcast, over the top, or directed spray. Irrigation or rainfall soon after application will wash residues off plant foliage and activate the material.
Gallery should be applied at 0.5 to 1 lb ai/A to control certain annual broadleaf weeds. To avoid possible injury, do not apply to unrooted liners or cuttings that have been planted in pots for the first time, or to pots less than 4 inches wide.
Goal is for use on conifers only and must be applied at 1 to 2 lb ai/A prior to budbreak or after the foliage has had time to harden off.
Lasso is for use on juniper and holly and is applied at 4 lb ai/A.
Ornamental Herbicide II (OH2) controls a wide spectrum of annual broadleaved weeds and grasses when applied at 3 lb ai/A.
Pendulum effectively controls many annual grasses and some broadleaf weeds when applied at 2 to 4 lb ai/A. For container-grown ornamentals, delay the first application to bareroot liners for 2 to 4 weeks.
Pennant provides excellent control of yellow nutsedge. Apply at 2 to 3 lb ai/A to control grasses, sedges, and some broadleaf weeds.
Regal O-O should be applied at 3 lb ai/A for control of many annual grasses and broadleaved weeds. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it.
RegalStar should be applied at 2.4 lb ai/A for control of many annual grasses and broadleaved weeds. It is especially effective on crabgrass, goosegrass, and chickweed. Delay application to new transplants until the soil has settled around the plant. Do not apply if the foliage is wet because the granules may stick to the foliage and burn it. Application can be made to actively growing or dormant ornamentals.
Ronstar provides excellent control of annual broadleaved weeds in container crops. Use it to control difficult weeds such as groundsel, galinsoga, and oxalis. Apply at 4 lb ai/A and repeat applications every 10 to 12 weeks. It does not control chickweed.
Rout controls a broad spectrum of annual broadleaved weeds and grasses when applied at 3 lb ai/A. Following planting and prior to herbicide application, irrigate with approximately l/2 inch of water to settle the potting medium. Allow the foliage to dry. Apply the herbicide and then apply another inch of water to wash any granules off the leaves and to activate the herbicide.
Snapshot TG applied at 2.5 to 5 lb ai/A provides very good control of both broadleaved weeds and grasses. Irrigate immediately after application.
Surflan should be applied at 2 to 4 lb ai/A to control a relatively broad spectrum of weeds for 6 to 8 weeks.
Treflan should be applied at 1 to 2 lb ai/A of the 4E formulation or 4 lb ai/A of the 5G formulation to control annual grasses. Irrigate immediately after application. Repeat application every 6 to 8 weeks.
XL should be applied at 4 to 6 lb ai/A to control certain annual grasses and broadleaved weeds. To avoid possible injury, do not apply XL 2G to unrooted liners or cuttings that have been planted in pots for the first time, or to pots less than 4 inches wide.
Hand pulling is the weed control method of last resort in container production operations. There are always some weeds that escape preventive measures. If these weeds are not pulled, they will thrive and rapidly spread in the irrigated, nutrient-rich container environment.
The postemergence grass herbicides Fusilade II, Vantage, and Prism can be applied over the top of most ornamentals to eliminate grasses that escape preventive weed control measures. All should be applied to actively growing grasses less than 8 inches tall. Allow at least 1 hour between application and irrigation.
Envoy should be applied at 13 to 34 fl oz per acre. For spot treatments, use a 0.5% solution (0.6 fl oz/gal). Add a nonionic surfactant at 0.25% v/v to all spray solutions (0.3 fl oz/gal or 1 pt/50 gal).
Fusilade II should be applied at 16 to 24 fl oz per acre. For spot treatments, apply 0.75 fl oz/gal. Add a nonionic surfactant at 0.25% v/v to all spray solutions (0.3 fl oz/gal or 1 pt/50 gal).
Vantage should be applied at 36 to 60 fl oz per acre. For spot applications use 2 to 3 oz/gal. Vantage includes a surfactant; no additional surfactant is needed.
DeMoss can be used to kill mosses, algae, lichens, and liverworts.
The following herbicides are registered for use on annual or perennial flowers or ground covers and vines. The plants for which they are registered are listed.
Betasan, Lescosan, others (bensulide)
Herbaceous plants: Alyssum, Aster, Bachelor's Button, Calendula, Campanula, Candytuff, Coral Bell, Daffodil, Dahlia, Daisy, Daphne, Freesia, Gazania, Gladiolus, Marigold, Narcissus, Pansy, Periwinkle, Primrose, Ranunculus, Sedum, Star Jasmine, Stock, Sweet Pea, Tulip, Wall Flower, Wild Strawberry, Zinnia.
Ground covers and vines: Ajuga, Hypericum, Ice Plant, Ivy, Myrtle, Pachysandra.
Devrinol, Hurdle (napropamide)
Herbaceous plants: Ageratum, African Daisy, Aster, Bird of Paradise, Bottle-brush, Dahlia, Daisy, Eucalyptus, Gardenia, Gazania, Geranium, Gladiolus, Heather, Hibiscus, Hosta, Lantana, Nandina, Narcissus, Petunia, Sedum, Zinnia.
Ground covers and vines: Ajuga, Bougainvillea, Carpobrotus, Delosperma, Dichondra, Erysimum, English Ivy, Euonymus, Ice Plant, Liriope, Osteospermum, Pachysandra, St. Johnswort, Vinca.
Eptam (EPTC)
Herbaceous plants: Ageratum, Alyssum, Amaranthus, Aster, Balsam, Begonia, Chrysanthemum, Dahlia, Daylily, Dianthus, Gazania, Marigold, Nasturtium, Pansy, Petunia, Sedum, Strawberry (ornamental), Sweet Alyssum, Zinnia.
Ground covers and vines: Ajuga, Ice Plant, Ivy, Pachysandra, Periwinkle, St. Johnswort.
The label warns against use on the following plants: Allium, Crocus, Daffodil, Hyacinth, Iris, Lily, Narcissus, Pepper (ornamental), Phlox, Salvia, Snapdragon, Tulip.
Factor, Barricade, RegalKade G (prodiamine)
Herbaceous plants: Achillea, Allium, Anemone, Aqualegia, Artemesia, Aster, Begonia, Bergenia, Boltonia, Cassia, Coreopsis, Delphinium, Dianthus, Echinacea, Euonymus fortunei, Fountain Grass, Gaillardia, Gentiana, Gladiolus, Gypsophila, Hedera helix, Helianthemum, Hemerocallus, Heuchera, Hosta, Iris, Lavendula, Lilium, Liriope, Lonicera japonica, Lythrum, Mondo Grass, Miscanthus, Narcissus, Osteospermum, Tree Peony, Physostegia, Rudbeckia, Russian Sage, Santolina, Saxifrage, Scabiosa, Sedum, Thalictrum, Tulip, Veronica, Vinca minor, Yucca.
Ground covers and vines: Euonymus fortunei, Hedera helix, Liriope, Lonicera japonica, Osteopermum, Vinca minor.
Gallery (isoxaben)
Herbaceous plants: African Daisy, Blue Fescue, Daffodil, Daylily, Fountain Grass, Miscanthus, Gardenia, Gazania, Heather, Hibiscus, Hosta, Hyacinth, Iris, Jasmine, Lantana, Nandina, Ribbon Grass, Tulip.
Ground covers and vines: Ice Plant, English Ivy, Euonymus, Liriope, Pachysandra, Periwinkle, St. Johnswort.
The label warns against use on the following plants: Ajuga, Hydrangea, Iberis, Sedum, Yucca. Do not use Gallery on tulip plants that have emerged more than 0.75 inch, gladiolus prior to emergence if the corms are less than 1 inch in diameter, or any bulbs while they are flowering. Do not use it on bedding plants or in areas where bedding plants will be planted within 1 year following application or on ground covers until they are established and well rooted.
OH2 (oxyfluorfen + pendimethalin)
Ground covers and vines: Euonymus, Pachysandra, Vinca.
Pendulum, Ornamental Weedgrass Control (pendimethalin)
Herbaceous plants: Ageratum, Anemone, Artemesia, Balloon Flower, Beach grass, Black-Eyed Susan, Blue Fescue, Butterfly Weed, Cabbage (ornamental), Caladium, California Poppy, Canna Lily, Carex, Celosia, Chrysanthemum, Columbine, Coneflower (purple), Coreopsis, Crocus, Daffodil, Daisy (african, shasta, oxeye), Daylily, Dianthus, Dicentra, Dusty Miller, Fountain Grass, Foxglove, Gallardia, Gazania, Geum, Gladiolus, Gypsophila, Hosta, Hyacinth, Hydrangea, Kale (ornamental), Lantana, Liatris, Lily, Marigold, Mondo Grass, Morningglory, Pansy, Pampas Grass, Penstmon, Petunia, Purple Loosestrife, Ribbon Grass, Rose, Sweet Flag, Tufted hair grass, Tulip, Yarrow.
Ground covers and vines: Ajuga, Cape Weed, Euonymus, Gazania, Ice Plant, English and Geranium Ivy, Liriope, Pachysandra, Periwinkle, St Johnswort, Sand Strawberry, Sedum, Verbena, Vinca, Zinnia. Use no sooner then 4 weeks after transplant: Alyssum, Aster, Begonia, Dahlia, Portulaca, Salvia, Snapdragon, Statice, Vinca.
Pennant (metolachlor)
Herbaceous plants: African Lily, Ageratum, Allium, Alyssum, Asclepias, Aster, Bellflower, Canna Lily, Carex, Chrysanthemum, Columbine, Coreopsis, Crocus, Daisy, Daylily, Delphinium, Dusty Miller, Gaillardia, Gazania, Geranium, Geum, Gladiolus, Hosta, Hyacinth, Hydrangea, Impatiens, Iris, Leopard's Bane, Lily, Lupine, Marigold, Muscari, Narcissus, Obedient Plant (Physostegia), Pampas Grass, Pansy, Petunia, Phlox, Potentilla, Primrose, Purple Loosestrife, Queen Anne's Lace, Rose, Scillia, Sedum, Snapdragon, Star of Bethlehem, Statice, Sweet William, Tulip, Veronica, Zinnia, Yucca.
Ground covers and vines: Ajuga, English Ivy, Euonymus fortunei, Ice Plant, Liriope, Pachysandra, Periwinkle, St. Johnswort.
Ronstar (oxadiazon)
Herbaceous plants: African Daisy, Carnation, Chrysanthemum, Gazania, Rose, Sedum.
Ground covers and vines: Ajuga, Carpobrotus, Euonymus, Honeysuckle, Iberis, Ice Plant, Algerian and English Ivy, Osteospermum, Pachysandra, Periwinkle.
Rout (oxyfluorfen + oryzalin)
Herbaceous plants: Candytuft, Iberis, Marigold, St. Johnswort, Salvia, Verbena.
Ground covers and vines: Bearberry, Bougainvillea, Cotoneaster, Euonymus.
Snapshot TG (isoxaben + trifluralin)
Herbaceous plants: Beech Grass, Blue Fescue, Daffodil, Daylily, Fountain Grass, Gazania, Gladiolus, Hosta, Hyacinth, Iris, Miscanthus, Mondo Grass, Plumbago, Ribbon Grass, Snow-in-Summer, Tulip.
Ground covers and vines: Cape Marigold, Carex, Descampsia, Euonymus, Honeysuckle, Ice Plant, Ivy, Japanese Painted Fern, Jasmine, Liriope, Pachysandra, Periwinkle, St. Johnswort. Do not apply to bedding plants or beds where they may be planted within 1 year.
Surflan (oryzalin)
Herbaceous plants: Aster, Astilbe, Baby's Breath, Bellflower, Bird of Paradise, Black-Eyed Susan, Blazing Star, Bleeding Heart, Blue Fescue, Bottle-brush, Caladium, California Poppy, Campanula, Cape Marigold, Carnation, Chrysanthemum, Coneflower, Coreopsis, Cosmos, Daffodil, Daisy, Dahlia, Daylily, Dianthus, Dusty Miller, Geranium, Geum, Gladiolus, Hosta, Hyacinth, Impatiens, Iris, Lupine, Marigold, Morningglory, Moss Rose, Nandina, Nasturtium, Nicotiana, Pansy, Petunia, Phlox, Portulaca, Rose, Sage, Salvia, Sedum, Snapdragon, Stock, Sunflower, Sweet William, Tulip, Yarrow, Yucca, Zinnia.
Ground covers and vines: Ajuga, Euonymus, Gazania, Honeysuckle, Ice Plant, Ivy, Liriope, Pachysandra, Periwinkle, Vinca.
Treflan (trifluralin)
Herbaceous plants: African Daisy, Ageratum, Asparagus Fern, Aster, Astilbe, Bachelor's Button, Balsam, Bellflower, Black-Eyed Susan, Calendula, Calliopsis, Cape Marigold, Chrysanthemum, Cosmos, Dahlia, Daisy, Dusty Miller, Forget-Me-Not, Four O'clock, Gaillardia, Germander, Gladiolus, Hens and Chickens, Impatiens, Lobelia, Lupine, Marigold, Morningglory, Moss Rose, Mourning Bride, Nasturtium, Nicotiana, Petunia, Phlox, Pink, Poppy, Rose, Salvia, Sedum, Shasta Daisy, Snapdragon, Snow-in-Summer, Snow-on-the-Mountain, Speedwell, St. Johnswort, Stock, Stoke's Aster, Strawberry, Sunflower, Sweet Alyssum, Sweet Pea, Sweet William, Verbena, Yarrow, Zinnia. Ground covers: Euonymus, Gazania, Ice Plant, Ivy, Liriope, Periwinkle, Vinca.
XL (oryzalin + benefin)
Herbaceous plants: Achillea, Baby's Breath, Bellflower, Bleeding Heart, Bird of Paradise, Blue Fescue, Bottle-brush, Cape Marigold, Cape Weed, Chrysanthemum, Coneflower (purple), Coreopsis, Daisy, Daylily, Dianthus, Eucalyptus, Gardenia, Gazania, Geranium, Geum, Gladiolus, Hibiscus, Hosta, Impatiens, Iris, Liatris, Liriope, Marigold, Mondo Grass, Nandina, Narcissus, Pampas Grass, Pansy, Petunia, Portulaca, Ranunculus, Rose, Rudbeckia, Salvia, Sedum (Stonecrop), Snapdragon, Tulip, Zinnia. note: Do not apply to tulip plants that have emerged to a height greater than three-fourths inch.
Ground covers and vines: Euonymus, Honeysuckle, Algerian and English Ivy, Ice Plant, Periwinkle, St. Johnswort.
Acclaim Extra (fenoxaprop)
Herbaceous plants: African Daisy, Astilbe, Baby Blue Eyes, Baby's Breath, Bachelor's Button, Begonia, Bellflower, Black-Eyed Susan, Bleeding Heart, Bluebell, Blue Flax, California Poppy, Calliopsis, Candytuft, Catchfly, Chrysanthemum, Coleus, Columbine, Coneflower, Coreopsis, Cosmos, Daisy, Dames Rocket, Daylily, English Wallflower, Forget-Me-Not, Gaillardia, Gayfeather, Gazania, Geranium, Gilia, Hosta, Iris, Leopard's Bane, Liatrus, Lily, Liriope, Maiden Pink, Phlox, Peony, Petunia, Pimpernel, Poppy, Red Yarrow, Rose, Shasta Daisy, Siberian Wallflower, Snapdragon, Snow-in-Summer, Soapwort, Statice, Sundrops, Sweet Alyssum, Sweet William, Wild Thyme, Yarrow, Zinnia.
Ground covers and vines: Ajuga, Ivy, Vinca.
Basagran T/O (bentazon)
Can be applied over the top of the ground covers listed below, but will injure most herbaceous plants contacted.
Ground covers and vines: English Ivy, Liriope, Pachysandra.
Envoy (clethodim)
It can be applied over the top of the following plants.
Herbaceous plants: Ageratum, Alyssum, Asparagus Fern, Chrysanthemum, Cinquefoil, Coleus, Cranesbill, Creeping Fig, Dahlia, Daylily, Gazania, Geranium, Iris, Jasmine Tobacco, Marigold, Partridgeberry, Petunia, Phlox, Pinks, Portulaca, Salvia, Saxifrage, Rockfoil, Sedum, Snapdragon, Sweet William, Touch-Me-Not, Verbena, Violet, Zinnia.
Ground covers and vines: Ajuga, English Ivy, Variegated Yellow Ivy, Variegated White Ivy, Green Liriope, Variegated Liriope, Moneywort, Creeping Charlie, Mondo Grass, Dwarf Mondo Grass, Periwinkle.
Fusilade II, Ornamec (fluazifop-p-butyl)
Group 1: It can be applied over the top of plants in this group.
Herbaceous plants: Ageratum, Alyssum, Astilbe, Bellflower, Bird of Paradise, Calendula, Campanula, Candytuft, Cassia, Chrysanthemum, Coleus, Coreopsis, Crownvetch, Daisy, Daylily, Dusty Miller, Eucalyptus, Fountain Grass, Gardenia, Gazania, Geranium, Hibiscus, Hollyhock, Hosta, Iris, Lantana, Lavender cotton, Liatris, Liriope, Marigold, Mesembryanthemum, Periwinkle, Petunia, Rose, Salvia, Sedum, Shasta Daisy, Snapdragon, Statice, Ornamental Strawberry, Sweet William, Yarrow, Yucca, Zinnia.
Ground covers and vines: Bougainvillea, Bearberry, Cotoneaster, Algerian and English Ivy, Grape ivy, Ice Plant, Myrtle, Pachysandra.
Group 2: It should be applied as a directed spray to prevent contact with the foliage of plants in this group.
Herbaceous plants: Bleeding Heart, Cinquefoil, Columbine, Fountain Grass, Gazania, Gladiolus, Lantana, Mondo Grass, Primrose.
Ground covers and vines: Ajuga, Japanese Honeysuckle, Juniper.
Vantage (sethoxydim)
It can be applied over the top of the following plants.
Herbaceous plants: Alyssum, Asparagus Fern, Aster, Begonia, Bird of Paradise, Bleeding Heart, Blue Fescue, Butterfly Weed, Camellia, Candytuft, Canna, Cape Weed, Carnation, Chrysanthemum, Cockscomb, Coleus, Coral Bells, Crownvetch, Dahlia, Daisy, Daylily, Dusty Miller, Euonymus, Gardenia, Gazania, Geranium, Gerbera Daisy, Gladiolus, Heather, Hibiscus, Honeysuckle, Hosta, Hydrangea, Impatiens, Iris, Jack-in-the-Pulpit, Jade Plant, Jasmine, Lantana, Lavender, Lily of the Valley, Liriope, Lobelia, Purple Loosestrife, Marigold, Mondo Grass, Moneywort, Moss Rose, Nandina, Nicotiana, Pampas Grass, Pansy, Pepper (ornamental), Periwinkle, Petunia, Phlox, Plumbago, Sage, Salvia, Sedum, Snapdragon, Speedwell, Statice, Stock, Sweet William, Verbena, Zinnia.
Ground covers and vines: Ajuga, Bittersweet, Bougainvillea, Cape Weed, Grape Ivy, Heather, Honeysuckle, Hypericum, Ice Plant, Ivy, Pachysandra, Periwinkle, Plumbago, St. Johnswort, Trumpet Vine, Vinca, Wisteria.