Landscaping with trees
Few ornamental trees offer the variety of tree shapes, sizes, flower colors and ornamental fruit as flowering crabapples. There are over 35 species and 700 cultivated varieties of crabapples and have been a part of the home landscape for many years.
Both apple trees and crab apples have clustered, five-petaled blossoms with 15 to 20 yellow stamens in the center. They typically begin blooming before the leaves unfold and are later joined by the young greenery.
Blossoms often open from pink or red buds and change to paler shades after opening, creating a beautiful pink cloud lasting several weeks. Asian crab apple specimens are usually preferred for ornament because their fruits are more colorful and last into the winter providing food for over-wintering birds.
Tree height may be from 6' - 50' with most in the 15' to 25' range. The varieties vary from weeping, spreading, columnar, vase-shaped to pyramidal which allows many opportunities for use in landscapes.
In some cases, crabapples have developed a poor reputation as a result of disease problems (scab, mildew, and fire blight) as well as susceptibility to certain insect pests such as Japanese beetle. However, extensive breeding and evaluation projects have resulted in numerous selections that are resistant to these problems.
Crabapples planted in average fertility soils and provided moderate amounts of organic matter need little additional fertilizer the first year. If you note that annual growth is less than 5" - 6" or leaves are small or pale green, then supplemental fertilizer is required.
If fertilizer is suggested, apply 2 - 3 pounds of actual nitrogen per 1,000 square feet of root zone area.
Example; a bagged fertilizer with an analysis of 20-5-10 (Nitrogen - Phosphorus - Potassium) apply 2 pounds nitrogen per 1,000 square feet which translates into 10 pounds of the 20-5-10 fertilizer spread beneath the trees over an area measuring 31.5' x 31.5' or its equivalent.
Pruning Crabapple Trees
Crabapples require little pruning other than to keep it in shape or from interfering with other landscape specimens. Rapidly growing shoots from branches, called water sprouts, rapidly growing shoots from roots or the base of the tree, called suckers, dead, diseased, damaged, and crossing branches should all be removed. Sometimes on dense growing crabapples, it's necessary to prune the center of the plant to allow additional sunlight and air movement.
Pruning 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.
Watering Requirements for Flowering Crabapples
If trees are well established after the first year, little additional watering is needed unless drought conditions prevail. In a drought situation water thoroughly and deeply every 2 - 3 weeks depending on the soil type and drought severity. Apply 2" - 6" of water at one time.
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.
Insect & Disease Common to Flowering Crabapples
Common crabapple diseases ...
Many of the newer 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.
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 that have varying degrees of susceptibility to disease, could still possess enough merit in the form of flowering characteristics, growth pattern, and shape. Understanding their limitations, these plants are perfectly acceptable in many landscape situations.
There are four diseases that pose a serious threat to crab apples: apple scab, a fungus characterized by black sooty spots or leaves and corky spots on fruits. Fire blight is a bacterium that turns twigs and branches black, eventually killing the tree. Cedar-apple rust is a fungus that creates rusty, corky spots on leaves and, if serious, can defoliate the tree. Less of a threat is powdery mildew is a white fungus that attacks leaves, flowers, and fruits during warm, humid weather and is unsightly.
Apple scab is a fungal disease that first affects emerging leaves in the spring, during moist conditions, and then moves to the fruit. Apple scab causes dark, leathery spots with a corky appearance on the fruit.
On the leaves, apple scab infections first appear in May or early June as olive-green or oil-soaked spots. On mature leaves, the infections appear as black, slightly raised velvety spots. As the disease develops, leaves turn yellow and drop prematurely. If the tree is heavily infected, defoliation can occur by early summer.
Control of apple scab can be achieved in a couple of ways:
Remove susceptible trees from the landscape and select other less susceptible disease-resistant crabapples.
Apply fungicides as leaves begin to emerge, at 2 weeks and again 4 weeks after the first application.
Frogeye Leaf Spot
Frogeye leaf spot is a fungal disease. It appears as 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 ranges from heavy defoliation to no impact. The impact greatly depends upon susceptibility of the species to this fungus.
Selecting resistant crabapples is the best way to avoid this disease.
This is a devastating disease caused by a bacterium, Erwinia amylovora. Symptoms appear as death of new terminal shoots in late spring or early summer. Shoots appear to be scorched by fire. Leaves remain attached to the blighted shoot which develops a characteristic curvature at the tip, commonly called a "shepherd's crook."
Fireblight progresses down through the shoot and forms a canker in the older tissue. Cankers are typically sunken areas that look 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:
Follow these guidelines to control fireblight: select plants 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 Commonly Affecting Flowering Crabapples
Flowering crabapples are relatively undamaged by most insects. Although various types of caterpillars, leafhoppers, leaf-rollers, leaf miners, and Japanese beetles may attack the tree, 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.
Avoid older cultivars when buying new crab apples
When purchasing crab apples avoid inferior older cultivars that are not resistant to many diseases and blights. Some of the worst are Almey, Bechtels, Eleyi, Evelyn, Flame, Hopa, Radiant, Red Silver, Sparkler and Vanguard.
|Malus 'Adams'||Adams Crabapple|
|Malus x atrosanguinea||Carmine Crabapple|
|Malus baccata 'Jackii'||Jackii Crabapple|
|Malus baccata mandshurica||Manchurian Crabapple|
|Malus 'Baskatong'||Baskatong Crabapple|
|Malus 'Beverly'||Beverly Crabapple|
|Malus 'Bob White'||Bob White Crabapple|
|Malus 'Centurion'||Centurion Crabapple|
|Malus 'Donald Wyman'||Donald Wyman Crabapple|
|Malus 'Doubloons'||Doubloons Crabapple|
|Malus 'Evelyn'||Evelyn Crabapple|
|Malus floribunda||Japanese Flowering Crabapple|
|Malus 'Harvest Gold'||Harvest Gold Crabapple|
|Malus hupehensis||Tea Crabapple|
|Malus 'Jewelberry'||Jewelberry Crabapple|
|Malus 'Katherine'||Katherine Crabapple|
|Malus 'Liset'||Liset Crabapple|
|Malus 'Prairifire'||Prairifire Crabapple|
|Malus 'Prince Georges'||Prince Georges Crabapple|
|Malus 'Professor Sprenger'||Professor Sprenger Crabapple|
|Malus 'Red Jade'||Red Jade Crabapple|
|Malus 'Robinson'||Robinson Crabapple|
|Malus 'Selkirk'||Selkirk Crabapple|
|Malus 'Sentinel'||Sentinel Crabapple|
|Malus sieboldii zumi 'Calocarpa'||Zumi Crabapple|
|Malus 'Snowdrift'||Snowdrift Crabapple|
|Malus tschonoskii||Tschonoski Crabapple|
|Malus 'White Angel'||White Angel Crabapple|
|Malus 'Zumirang'||Zumirang Crabapple|