Key wheat management decisions need to be made at certain growth stages. Exact growth stages cannot be determined by just looking at the height of the crop or based on calendar dates. A careful examination of the developing crop is needed to tell growth stages apart. Correct growth stage identification and knowledge of factors that affect grain yield can enhance management decisions, avoiding damage to the crop and unwarranted or ineffective applications. These decisions can make wheat production more profitable. Several scales can be used to identify wheat growth stages, including the Feekes and Zadoks scales. Here we focus on the Feekes Growth Scale.
|Figure 1. Wheat main stem and tiller.|
Using this scale, growth stages are identified and assigned numerical codes based on the occurrence of key developmental events such as tillering, leaf and head emergence, and flowering. Since growth and development usually vary among tillers and across the field, it is important to sample and examine primary tillers at multiple locations to come up with a representative growth stage for the field. Commonly used sampling schemes include walking and examining tillers across the field at regular intervals along a zig-zag or M-shaped pattern, but the uniformity of the field and visual differences in crop development are also very useful for determining how and where to sample tillers. Usually the crop (or a section of a field) is said to be at a given growth stage when approximately 50 percent of the primary tillers reach that growth stage.
Feekes 1.0: Emergence
The number of leaves present on the first shoot (main stem) can be designated with a decimal. For example, 1.3 is a single shoot with three leaves unfolded. The most significant event in achieving high yields is stand establishment, i.e, the number of plants or tillers per square foot. Late-planted wheat has less time to tiller and should be planted at a higher seeding rate to compensate for fewer tillers.
Feekes 2.0: Beginning of Tillering (usually in fall)
A tiller is a shoot that originates at the coleoptilar node. Tillers share the same root mass with the main stem (Figure 1). During tillering, the major management consideration is whether stands are adequate to achieve yield goals. Management inputs will not compensate for skimpy or erratic stands caused by insects, seedling diseases, poor seed quality, herbicide injury, etc. A producer may want to apply 20 to 30 pounds per acre starter N to promote tillering, especially if planting without tillage. Excess N applied at this time leads to a lush, vegetative growth which makes the crop more susceptible to winterkill and foliar fungal diseases. Adequate phosphorus (P) and soil pH above 6.0 are needed for good root and tiller development.
Feekes 3.0: Tillers Formed (late fall or early spring)
Winter wheat can continue to tiller for several weeks. Depending upon the planting date and weather conditions, tillering can either be interrupted by or completed prior to the onset of winter dormancy. Most of the tillers that contribute to grain yield are completed during this stage.
Winter wheat plants are prostrate or “creeping” at this stage. In the spring, between Feekes 3.0-4.0, wheat “greens-up.” Green-up is not a definable growth stage, but occurs when the new growth of spring has covered the dead tissue from winter giving the field a solid green color. Spring N should not be applied before green-up.
Feekes 4.0: Beginning of Erect Growth (March-April)
Most tillers have been formed by this stage, and the secondary root system is developing. Winter wheats, which may have a prostrate growth habit during earlier vegetative developmental stages, begin to grow erect at Feekes 4. Leaf sheaths thicken. The key management step at Feekes 4.0 is continued scouting for insects and weed infestations.
Feekes 5.0: Leaf Sheaths Strongly Erect (early- to mid-April)
Further development of the winter wheat plant beyond Feekes 4 requires vernalization, or a period of cool weather between Feekes 1 and Feekes 4. After the appropriate amount of chilling, followed by the resumption of growth, the growing point (located below the soil surface) differentiates. At this stage of growth, the size of heads—or number of spikelets per spike—is determined. No effect on yield is expected from tillers developed after Feekes 5.0.
Nitrogen applied at Feekes 5.0 can affect the number of seeds per head and seed size, but not the number of heads per square foot or the number of spikelets per head. This is an ideal stage of growth for the spring topdress N application. Weed control decisions should be made before or during Feekes 5.0 with 2,4-D and similar phenoxy herbicides being applied during Stages 5 and 6. This is also a good stage to begin scouting for foliar diseases.
Feekes 6.0: First Node Visible (mid-late April)
Prior to Feekes 6.0, the nodes are all formed but sandwiched together so that they are not readily distinguishable. At 6.0, the first node is swollen and appears above the soil surface. This stage is commonly referred to as “jointing.” Above this node is the head or spike, which is being pushed upwards eventually from the boot. The spike at this stage is fully differentiated, containing future spikelets and florets. Figure 2 shows a split wheat stem showing the developing wheat spike.
Growers should remove and carefully examine plants for the first node. It can usually be seen and felt by removing the lower leaves and leaf sheaths from large wheat tillers (Figure 3). A sharp knife or razor blade is useful to split stems to determine the location of the developing head. The stem is hollow in most wheat varieties behind this node.
|Figure 2. Split wheat stem showing developing spike.||Figure 3. Feekes Growth Stage 5 showing no node on the main wheat stem and Feekes Growth Stage 6 with the first node visible. Note: Lower leaves and leaf sheaths have been removed.|
By Feekes 6.0, essentially all weed-control applications have been made. Do not apply phenoxy herbicides such as 2,4-D, Banvel or MCPA after Feekes 6.0, as these materials can be translocated into the developing head, causing sterility or distortion. Sufonyl-urea herbicides are safe at this growth stage, but for practical reasons, weed control should have been completed by now. Small grains can still show good response to N topdressing at this time.
Feekes 7.0: Second Node Becomes Visible (late April-early May)
|Figure 4. Feekes Growth Stage 8 where flag leaf is visible, but still rolled up.|
This stage is characterized by the rapid expansion of the head and a second detectable node. Look for the presence of two nodes—one should be between 1.5 and 3 inches from the base of the stem and the other should be about 4 to 6 inches above the base of the stem. These nodes are usually seen as clearly swollen areas of a distinctly different (darker) shade of green than the rest of the stem. Note: the upper node may be hidden by the leaf sheath; you may have to run your fingers up the stem to feel for it. If only one node is present, then your wheat is still at Feekes Growth Stage 6. Wheat will still respond to N applied at Feekes 7.0 if weather prevented an earlier application; however, mechanical damage may occur from applicator equipment.
Feekes 8.0: Flag Leaf Visible, but Still Rolled Up (late April-early May)
This growth stage begins when the last leaf (flag leaf) begins to emerge from the whorl (Figure 4). This stage is particularly significant because the flag leaf makes up approximately 75 percent of the effective leaf area that contributes to grain fill. It is therefore important to protect and maintain this leaf heathy (free of disease and insect damage) before and during grain development. When the flag leaf emerges, three nodes are visible above the soil surface. To confirm that the leaf emerging is the flag leaf, split the leaf sheath above the highest node. If the head and no additional leaves are found inside, Stage 8.0 is confirmed and the grower should decide whether or not to use foliar fungicides to manage early-season and overwintering foliar fungal diseases. This decision should be based upon the following considerations:
- Is a fungal disease present in the field?
- Is the variety susceptible or are weather conditions favorable (wet and humid) for rapid spread and development of the disease(s) found in the field?
- Does the crop yield potential warrant the cost of application of the fungicide in question to protect it?
- Is the crop under stress?
If a positive answer applies to the first three questions, and a negative response to the last, plans should be made to protect the crop from further damage. Check product labels and apply as soon as possible. In most situations, the greatest return to applied foliar fungicides comes from application at Feekes Stages 8 through 10. Nitrogen applications at or after Feekes 8.0 may enhance grain protein levels but are questionable with respect to added yield. Moreover, additional N may increase the severity of some foliar diseases, particularly the rusts.
Feekes 9.0: Ligule of Flag Leaf Visible (early May)
Stage 9.0 begins when the flag leaf is fully emerged from the whorl with the ligule visible (Figure 5). From this point on, leaves are referred to in relation to the flag leaf (i.e., the first leaf below the flag leaf is the F-1, the second leaf below is the F-2, and so forth). After the flag leaf emergences, army worms can seriously damage yield potential.
|Figure 5. Feekes Growth Stage 9 where the ligule of the flag leaf is visible.||Figure 6. At the boot stage, the head is fully developed and can be easily seen in the swollen section of the leaf sheath below the flag leaf.|
Feekes 10.0: Boot Stage (mid-May)
At the boot stage, the head is fully developed and can be easily seen in the swollen section of the leaf sheath below the flag leaf (Figure 6). This is another important growth stage for making fungicide applications for foliar disease management, particularly late-season diseases such as Stagonospora leaf and glume blotch and rusts.
Feekes 10.1-10.5: Heading (mid- to late-May)
|Figure 7. Wheat flag leaf, ligule, awns and spike (or head) at Feekes 10.5.||Figure 8. Feekes Growth Stage 10.5.1 or beginning flowering is often marked by the extrusion of anthers from florets in the center of the spike.|
Heading marks the emergence of the wheat head from the leaf sheath of the flag leaf, and is subdivided into stages based on how much of the head has emerged. Stage 10.5 is shown in Figure 7.
- 10.1 Awns visible, head beginning to emerge through slit of flag leaf sheath.
- 10.2 Heading one-quarter complete.
- 10.3 Heading one-half complete.
- 10.4 Heading three-quarters complete.
- 10.5 Heading complete.
Feekes 10.5.1-10.5.3: Flowering (mid-May to early-June)
- 10.5.1 Beginning flowering. This stage is often marked by the extrusion of anthers from florets in the center of the spike (Figure 8). For that reason, this growth stage is also referred to as “anthesis.” Although, on rare occasions under growing conditions in Ohio, flowering may occur without anthers being extruded or with anther extrusion occurring after flowering, depending on the weather and the variety. Feekes 10.5.1 is the growth stage at which fungicides are recommended and are most effective against wheat head scab and vomitoxin.
- 10.5.2 Flowering complete at the top of the spike.
- 10.5.3 Flowering complete at the base of the spike.
Wheat is self-pollinating. Most florets are pollinated before anthers are extruded. Although tillers have developed over several weeks, bloom in a given wheat plant is usually complete four to five days after heading. The grain-fill period of wheat varies somewhat, depending upon climate. It is typically as little as 13 days in high-stress environments, and may exceed 20 days in high-yield, low-stress environments. After Feekes Stage 10.5.3, remaining growth stages refer to ripeness or maturity of the kernel.
Feekes 10.5.4-11.4: Ripening and Maturation
- 10.5.4 Kernels watery ripe, clear fluid can be squeezed from the developing kernel.
- 11.1 Milky ripe, milk-like fluid can be squeezed out of the kernels when crushed.
- 11.2 Mealy ripe, material squeezed out of the kernel has a doughy consistency.
- 11.3 Kernel hard, but dividable with thumbnail (late June).
- 11.4 Harvest ready. Kernel is hard and not dividable with thumbnail (late June-early July).
At maturity, timely harvest is important. Risks of delayed harvest include disease, lodging and seed sprouting which ultimately reduce grain yield and test weight.
|Table 1. Wheat morphological terms.|
|Anther||The male (pollen-producing) part of the flower.|
|Awn||The bristles on the wheat head (spike).|
|Coleoptile||Protective sheath covering the emerging shoot.|
|Flag leaf||The last leaf to emerge before the head (spike).|
|Floret||Each individual flower (containing anthers and stigma). Several florets form a single spikelet.|
|Spike||Also known as the wheat head.|
|Spikelet||The basic unit of a wheat flower. Each spikelet consists of at least three florets.|
|Stigma||The female (pollen-receptor) part of the flower.|
|Tiller||A shoot originating from the main stem from the coleoptilar node.|
Original Author: James E. Beuerlein, retired. (Originally published in 2001.)