Ohio State University Extension Fact Sheet

Ohio State University Fact Sheet

Horticulture and Crop Science

2021 Coffey Road, Columbus, OH 43210-1086


Selection, Care, and Use of the Ornamental Crabapple

HYG-1029-96

Erik Draper
James Chatfield

There are few plants that create greater intrigue or visual impact during all four seasons than the flowering crabapple. In the spring all eyes are enticed with delicate colors offered by emerging leaves and buds. Unopened flower buds may hint of one color and as flowers open, other hues are revealed in a spectacular floral display. As flowers fade the rich foliage offers another subtle contribution to the landscape.

As autumn arrives crabapple foliage and fruit transform to match the vibrant colors of an artist's palette. Falling leaves reveal the glorious color of the fruit. The snow of winter accents fruit, branches, and tree shape. It is no wonder crabapples are called "jewels of the landscape."

Flowers

Depending on the cultivar and spring temperatures, full bloom in Ohio could occur as early as late April or delay until mid-May. Flowers are classified as single (five petals), semi-double (six-ten petals), or double (more than 10 petals). Double-flowering crabapples retain their flowers longer than other types, but fruiting is usually sparse.

Blossom colors range from pearly white through delicate pinks to a deep red. There are even cultivars with coral or salmon colored flowers.

Figure 1. Malus baccata 'Jackii.' Note the clean, glossy green foliage and shiny burgundy fruits.

Fruit

Apples and crabapples are in the rose family, Rosaceae, in the genus Malus. Crabapples are differentiated from apples based on fruit size. If fruit is two inches in diameter or less, it is termed a crabapple. If the fruit is larger than two inches, it is classified as an apple.

Fruit is borne in the summer and fall. Colors range from dark-reddish purples through the reds and oranges to golden yellow and even some green. On certain selections the fruit can remain attractive well into the late winter. The larger fruited cultivars offer a bonus because the fruit can be spiced or used in jelly.

Growth Habit and Size

Crabapples have diverse growth habits or tree shapes. The shapes consist of weeping (pendulous), rounded, spreading (horizontal), upright (columnar), vase-shaped, and pyramidal.

Flowering crabapples vary greatly in size. At maturity, certain cultivars will only attain a height of eight feet, while others will tower to heights greater than 40 feet. However, most flowering crabapples reach mature heights of 15 to 25 feet.

Due to their versatility, crabapples make excellent choices for use around homes, schools, parks, public and commercial buildings, and in highway plantings.

Figure 2. Malus 'Bob White.' Note golden-yellow small fruits in the November landscape.

Site Requirements

Flowering crabapples are adaptable but thrive in rich loam type soil (a combination of clay, silt, and sand). Regardless of soil type, good drainage is a must for tree health. Crabapples grow best in a moist, slightly acidic soil with a pH of 5.0 to 6.5. Excessively moist areas and low spots should be avoided. On the other hand, relatively dry sites can be tolerated by crabapples if plant stresses are minimized during the first year after transplanting.

Plant stress, evidenced as unhealthy appearance (e.g. leaf scorch, poor leaf color), is a response to unfavorable environmental conditions. Drought stress, for example, is due to a lack of water, either from rainfall or irrigation. Water is essential for every life function of the plant. However, too much water or over-watering, a persistent saturation of the roots, can lead to root rot and eventual plant death. Other plant stresses include too much shade, insect damage, infectious diseases, and physical damage from lawnmowers, weed-eaters, animals, and children playing.

Full sun exposure, 8 to 12 hours of direct sun, is required for optimal development of fruits and flowers. Most flowering crabapples are hardy in Ohio and can endure the colder temperature extremes of zone 4 on the USDA Plant Hardiness Zone maps.

Planting and Establishment

Tree health and vigor depends upon proper site selection and preparation. Before planting, have the soil tested to assure proper pH and nutrient levels. If necessary, make any adjustments to the soil before planting.

Flowering crabapples may be planted almost any time of the year. Balled and burlapped (B&B) stock and containerized trees can be planted any time after spring frosts end through fall until about three weeks before the ground freezes. However, bare root trees should only be planted in the spring. Bare root trees become too stressed if planting is delayed past early spring.

Every effort should be made to keep roots or the root ball from drying out before planting. For bare root trees, the planting hole should be dug wide and deep enough to allow for the natural extension of the root system. None of the roots should be cramped or bent to fit into the hole. This can result in girdling (strangling) roots that will slowly kill the tree. Damaged roots should be pruned just above the break or damaged area prior to planting.

For containerized or balled and burlapped trees, a saucer-shaped hole should be dug. The overall size should be at least two times wider than the root ball diameter. The center depth of the saucer should be the exact height of the root ball. This allows the burlap to be untied and placed down into the hole at planting. Make sure all strings holding the burlap at the base of the trunk are removed or these may damage or even kill the tree in later years.

Containerized plants should be removed from the pots just prior to planting. Using a small, sharp knife slice one inch deep into the compacted root mass, from top to bottom, in at least three different areas. This will help prevent the formation of girdling roots.

Most flowering crabapples are grafted onto other root systems (rootstocks) which must be planted at the original depth they were in the nursery or slightly higher (1-2" maximum). "Long term root decline" may occur if trees are transplanted too deep. When tree roots are buried deeper than originally grown, the tree can languish for years, resulting in lackluster appearance and health, and eventually death.

Backfill the planting holes with a 50-50 mixture of the original soil and organic matter (e.g. leaf humus, compost, peat moss). Do not pack backfill around the root ball. Instead, use water to help settle the soil around the roots when the hole is three-quarters full. When the water has drained, backfill the hole completely and water again.

Place a thin layer of mulch, no more than two inches deep, around the tree to help reduce water loss. Turfgrasses will compete with the young tree for water and nutrients. Keep turfgrasses away from the rooting area of the planted tree to provide optimal conditions for tree establishment and survival. The young tree will need about one inch of water, rain or otherwise, per week. These subsequent weekly waterings, during the first year, are crucial for tree establishment.

Figure 3. Malus 'Sentinel.' Note the carmine red buds opening to white flowers.

Maintenance

Fertilizer

When crabapples are planted in a soil of average fertility and provided moderate amounts of organic matter, they need little additional fertilizer the first year. However, if annual growth is less than five to six inches or leaves are small or pale green, then fertilizer is essential. In general, apply two to three pounds of actual nitrogen per 1,000 square feet of root zone area. For more details on fertilizer analysis see Extension Fact Sheet #4022.

For example, for a fertilizer with an analysis of 20-5-10 (These numbers essentially refer to the percentages of nitrogen, phosphorus, and potassium--NPK--in the bag), to apply two pounds nitrogen per 1,000 square feet, use ten pounds of a 20-5-10 fertilizer spread beneath the trees over an area measuring 31.5 feet by 31.5 feet or its equivalent. See Extension Fact Sheet #1002 for more details on fertilizing trees.

Pruning

Crabapples require little pruning. Watersprouts (rapidly growing shoots from branches), suckers (rapidly growing shoots from roots or base of tree), dead, diseased, damaged, and crossing branches should be removed. Occasionally pruning is necessary to open up the center of the plant to sunlight and air movement or to remove a wayward branch.

When pruning is done it should be completed before early June. By mid-June to early July, flower buds for the next season are beginning to form in most crabapples. Pruning after July will reduce floral display and fruiting for the following year.

Irrigation

If trees are well established after the first year, little additional watering is needed unless drought conditions prevail. In a drought situation it is necessary to water thoroughly and deeply every two or three weeks. Depending on the soil type and drought severity, two to six inches of water should be applied at each watering interval.

If crabapples are not watered during periods of drought they will not collapse and die. However, the trees will use most of their carbohydrates to merely exist and survive. As a result, the next year's floral and fruit display will likely be diminished.

Figure 4. Malus 'Molten Lava.' Note red fruits contrasted with yellow-orange fall foliage color of spreading, cascading branches.

Diseases

Many new flowering crabapples are disease resistant or tolerant. Disease resistance involves genetic resistance to infection by disease causing organisms. Disease tolerance implies the plant may be affected by certain diseases but are of little health significance to the plant.

Unfortunately, few crabapples possess all desirable characteristics of exquisite flowers, fruit, foliage, growth habit, and disease resistance. This does not mean that other cultivars should not be used. Many crabapples are slightly susceptible to certain diseases and yet have great merit. By accepting and understanding their limitations, these plants are perfectly acceptable in many landscape situations.

Apple Scab

This fungal disease first affects emerging leaves in the spring, during moist conditions, and then moves to the fruit. Scab causes dark, leathery spots with a corky appearance on the fruit. On leaves, scab infections first appear in May or early June as olive-green or oil-soaked spots. On mature leaves, the infections appear as black, velvety spots that are slightly raised. As the disease develops, leaves turn yellow and drop prematurely. If the tree is heavily infected, defoliation can occur by early summer.

Control can be achieved one of two ways. Remove the trees that are highly susceptible and select other less susceptible disease-resistant crabapples. Alternatively, apply fungicides as leaves begin to emerge, at two weeks and again four weeks after the first application. See Extension Fact Sheet #3003 for specific information on apple scab.

Frog-eye Leaf Spot

Symptoms of this fungal disease are typically small, dark brown spots (dead leaf tissue) outlined by a thick, dark purple circle. Frog-eye leaf spot is found commonly on many flowering crabapples and its effect, from heavy defoliation to no impact, depends upon susceptibility to this fungus.

The best course of action is to select crabapples which are resistant or tolerant to this disease.

Fireblight

This devastating disease is caused by a bacterium, Erwinia amylovora. Symptoms appear as death of new terminal shoots in late spring or early summer. These shoots appear to be scorched by fire. The leaves remain attached to the blighted shoot which develops a characteristic curvature at the tip, commonly called a "shepherd's crook."

Fireblight often progresses down through the shoot and forms a canker in the older tissue. Cankers are typically sunken areas that are dark brown to purplish in color. An orange or amber gum may ooze from these infected parts. As the bark dies, the area becomes slightly depressed.

Control of fireblight can be easily achieved if these guidelines are followed. First and foremost, select plants that are genetically resistant to fireblight. If that is not an option then sanitation, removal, and disposing of blighted branches and shoots are the best alternatives.

Insects/Pests

Flowering crabapples are relatively undamaged by most insects. Although they are frequented by various types of caterpillars, leafhoppers, leaf-rollers, leafminers, and Japanese beetles, these pests rarely cause significant damage to the tree. The nest forming caterpillars (i.e. eastern tent caterpillar, fall webworm) are easily pruned out or removed with a gloved hand.

Japanese beetles and other pests are easily controlled with insecticides. Control may be warranted in young trees if one-third to one-half of the foliage is affected.

Recommendations

These recommendations are a small synopsis from a more thorough discussion of the ornamental ratings of crabapples by the authors. For a more in-depth commentary of crabapple seasonal profiles see "Aesthetic Evaluation of Crabapples at the Secrest Arboretum in Wooster, Ohio: 1993-1994," Special Research Circular 142.

Weeping-Spreading Form

Malus 'Molten Lava': Highly rated crabapple. White flowers, yellow-orange fruits, 8 to 10 feet. Outstanding weeping-spreading crabapple for much of the year, and never mediocre. Fruits and yellowing fall foliage provide a fiery cascading image. After the fruit falls, the remaining pedicels provide an attractive feathery winter effect that complements the elegant branching structure. Trace of scab, but not a factor ornamentally.

M. 'Red Jade': White flowers, red fruits, 8 to 10 feet. Great strength is its attractive spreading habit, providing interest through the year, especially in winter. Impressive blossom and fruit displays. Strap-like leaves and twisting of petioles are characteristic of this cultivar.

M. 'Mary Potter': White flowers, red fruit, 10 to 15 feet. Very attractive through the summer months due to pleasing spreading growth habit. Trace of scab, but overall very clean foliage. Exfoliating trunk bark is an intriguing feature.

M. 'White Cascade': White flowers, small yellow fruits, 10 to 15 feet. Exquisite flower display with waterfalls of cascading blossom covered branches. Provides an effective presentation from early to mid summer due to its attractive weeping form. However, moderate scab and a trace of frogeye reduce its appeal in late summer.

Small Spreading Form

M. sargentii: White flowers, red fruits, 6 to 10 feet. Attractive low-spreading growth habit is an excellent feature, especially as plant ages. Resistant to scab with just a trace of frogeye leafspot. Fruits tend to shrivel early in fall, diminishing winter impact. M. sargentii 'Rosea' differs from the species in that it has rose-pink buds.

M. 'Red Jewel': White flowers, cherry red fruit, 10 to 15 feet. Attractive, persistent red fruits are outstanding, complementing its small, delicate growth habit. Most effective through fall and winter months. Foliage is relatively scab free with a trace of frogeye.

Large Rounded Form

M. 'Donald Wyman': Highly rated crabapple. White flowers, bright red fruits, 20 feet. Lustrous green foliage, good overall growth habit, and outstanding small glossy fruits make this tree exceptional. Traces of scab and frogeye on leaves are negligible. Alternate flowering pattern results in "off" or sparse bloom, though this selection typically has outstanding blooms.

M. 'Sugar Tyme': White flowers, brilliant red fruits, 15 to 18 feet. Marvelous fruit and flower displays. Foliage remains clean with only traces of scab and frogeye leafspot. Excellent all-purpose tree due to captivating fruit display which begins in mid-fall and persists through the winter.

M. baccata'Jackii': White flowers, maroon-red fruits, 30 to 40 feet. Glossy, large, disease-free, deep green leaves are an exceptional ornamental feature. Handsome overall form and structure. Fruit somewhat sparse, but shiny and in attractive clusters; becoming soft in November. Large tree is mediocre throughout winter months.

M. 'Bob White': White flowers, yellow fruits, 20 feet. Outstanding feature from November through February is persistent, small, firm yellow-gold fruits maturing by January into orange-gold color. Foliage relatively clean with just a trace of scab and frogeye leafspot. Only mediocre during spring and summer months.

Upright Form

M. 'Sentinel': White with pink tinged flowers, red fruits, 15 to 20 feet. Vase-shaped upright habit. Pink buds opening to tinged white flowers are sensational. Trace of scab does not diminish the ornamental effect of this tree. Persistent fruits through the winter are nice but can detract during spring and early summer until they fall off.

Unique Growth Form

M. 'Strawberry Parfait': Pink flowers, fruits start yellow with increasing red blush. Unusual erratic upright-spreading growth habit is one of best features. Good firm fruits into the winter. Foliage was striking as it developed along the upright stems in the spring. Excellent scab resistance with a trace of frogeye leafspot. Unusual shape is not for every landscape.


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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.

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