Crabapple, Bob White - Malus 'Bob White'

Bob White Crabapple - Malus 'Bob White' [2]
Rose Family: Rosaceae
Ormiston Roy Crabapple is cited as one variety resistent to apple scab [4]
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Bob White Crabapple's white flowers are a spring highlight. Newer varities are more disease
resistant, but this spreading tree still yields deep red fruits and winter food for birds.

One of the most stunning trees used in the Midwestern landscape is the crabapple. Most crabapples are small trees, making them an appropriate size for most home gardens, but their spring blooming is prolific and showy. They are exciting throughout the year, with craggy branches and persistent fruits in winter.

Crabapples (Malus) are the most stunning of spring flowering trees for Midwest landscapes and are a great choice for the home garden. Many of them are small in stature and can maintain visual interest throughout the changing seasons (spring flowers, fall fruit, textured bark and craggy branches in winter).

There are about 55 different species in the genus Malus, and there are innumerable cultivars available in the landscape trade. The Arboretum's Crabapple Collection was started in 1924. Part of this collection on the West Side participated in the National Crabapple Evaluation Program which evaluated new and disease-resistant varieties. As a result of the multi-year evaluation and additions, it has transformed into the West Side Malus collection which now contains 60 different kinds and over 140 specimens with highly desirable qualities.

Some of the specimens in this collection are almost large enough to be considered shade trees, while others are quite small. There is a great variety of shape as well, from wide to upright and narrow, weeping, and multi-stemmed. There is variety in flower color, ranging from white to pink, red, purple, and crimson. Some flower buds will be one color, and then open up to a completely different color! Fruits range in size from smaller than a pea, to nearly the size of most apples; they can be red, purple, orange, yellow, or green. Some of the smaller fruits persist on the tree throughout winter, providing a splash of color in the cold months. [1]

Bob White Crabapple - Malus 'Bob White', Morton Arboretum acc. 37-84*1, from a planting, is 25 years old [2]

Crabapples are versatile, small, ornamental trees used in the urban landscape. Crabapples bloom in spring, usually in May, bearing flowers that vary a great deal in color, size, fragrance, and visual appeal. It is common for flower buds to be red, opening to pink or white flowers. The fruit ripens between July and November, and varies in size from ¼”to 2” long or wide. Crabapples thrive in full sun and grow best in well drained, slightly acidic soils (pH 5.5-6.5); however, they will grow well in many soil types. Most crabapple selections tolerate the cold winters and hot, dry summers prevalent in the Midwest.

For many years, crabapple cultivars have been selected on the basis of their flowers, but with some cultivars, undesirable features, such as disease problems and early fruit drop, outweigh their short-lived spring beauty. No single cultivar can fulfill every landscaping need. Consider the following information when choosing a crabapple cultivar for your landscape. [3]

Bob White Crabapple Foliage

DISEASE
Disease resistance should be your first consideration. Many resistant cultivars are available and recommended in order to avoid the most common disease problems. Before making a selection, keep in mind that not all crabapples do well in every location. Disease intensity varies from region to region, and disease strength can vary from year to year. For instance, some crabapples will be more prone to disease susceptibility in areas with greater rainfall than in drier climates. Careful consideration of the following information will be helpful in choosing the right crabapple cultivar. There are four diseases that seriously affect crabapple:

Apple scab is one of the most serious diseases from an aesthetic standpoint, but usually not a serious threat to the health of the tree. It is a fungal disease, which develops in cool, wet springs. On susceptible crabapples, apple scab causes spotting of the leaves, premature defoliation, and unsightly spots on the fruit. There are numerous cultivars that are resistant or very tolerant (still susceptible but with little defoliation) so choose one based on its resistance.
Cedara-apple rust is a less serious leaf-spotting disease common to our native crabapple cultivars. It is usually a problem in areas where native junipers (Juniperus) are planted. Selecting resistant cultivars can control this disease.

Powdery mildew is a fungal disease that can cause considerable damage to leaves and fruit of susceptible cultivars without threatening the health of the tree. Poor air circulation, close association with susceptible apple cultivars, and wet, humid weather conditions will greatly influence disease incidence and severity. Fire blight is a serious bacterial disease of crabapples. Though it is less common then the others, if left untreated it can be fatal to susceptible crabapple cultivars. Select resistant cultivars. [3]

References

Morton Arboretum, Crabapple: A Tree For All Seasons
Bob White Crabapple - Malus 'Bob White', Morton Arboretum acc. 37-84*1, photographed May 4th, 2009. Photographer: Bruce J. Marlin
Morton Arboretum, Crabapples for the Home Landscape
Morton Arboretum, Plant Health Care Report, Issue 2009.07, May 22- May 28, 2009

Excerpts from Morton Arboretum articles used with permission.

Pink Spires Crabapple - Malus 'Pink Spires'

Purple Prince Crabapple - Malus 'Purple Prince'

Mary Potter Crabapple - Malus 'Mary Potter'

American Masterpiece™ Crabapple - Malus 'Amaszam'

Klehm Prairie Crabapple - Malus ioensis 'Klehmii'

Christmas Holly Crabapple - Malus 'Chrishozam'

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