Saturday, March 31, 2012

The Beauty of the Flowering Crab Tree


Crabapple trees are often called the jewels of the landscape.  Indeed, in every season, they are beautiful.  There are few plants that create greater visual impact during all four seasons than the flowering crabapple. In the spring, delicate colors are 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.

To keep your tree looking beautiful every season it is imperative that you keep the tree healthy and free from the diseases that crabtrees commonly catch.

Flowering crabapples should 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 and can endure the colder temperature extremes of zone 4 on the USDA Plant Hardiness Zone maps.

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.

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.

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. 

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.

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.

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.

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.

Trees are a big investment and you don't want to leave your trees unprotected.  If you are unsure of how to care for your trees, or simply don't have the time, then you can trust your trees to Trees "R" Us, Inc. We have 5 certified arborists on staff to address your tree care questions and provide you with tree maintenance plans.  Our Plant Health Care division specializes in fertilization and treating and preventing tree diseases like Apple Scab.  The season is upon us.  You need to keep your trees healthy starting now.  Contact Trees "R" Us, Inc. to protect your trees and your investment.  Check us out at www.treesrusinc.com.  Call or email to set up your Plant Health Care consultation at 847-913-9069 or nick@treesrusinc.com.

Thanks for reading ,
Nick

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