Photo by Mark MacLennan
By Alan Branhagen, Arboretum Director of Operations
Crabapples (and apples!) are in the Rose Family in the Genus Malus which is of North American origin. They spread to Eastern Asia (and westward to Europe) which now has the greatest diversity of species. Apples evolved in the Tian Shan of western China–Kyrgyzstan-Tajikistan and spread globally by humans starting with the Silk Road.
Minnesota has one native species: prairie crabapple (Malus ioensis) and there are several other American species and subspecies. The rare Biltmore crabapple (Malus glabrata), from the American Southeast thrives in the Arboretum’s collection. Native crabapples are the most fragrant and latest blooming crabapples of soft shell-pink, with added ornamental exfoliating bark. Unfortunately, they are very susceptible to foliar maladies. Their fruit (which drops when ripe in fall) looks like a small Granny Smith apple, used mainly for making pickles.
Many crabapples (besides the native species) are susceptible to foliar diseases “Malus maladies” including apple scab, cedar-apple rust and fire blight. These are usually just cosmetic issues that diminish some crabapples’ ornamental value in traditional landscapes, however these cultivars are still suited to historic landscapes or in the case of native species in natural landscapes and restorations. Note that disease resistance of varieties can change as diseases mutate, some formerly resistant crabapples like ‘Red Splendor’ were once resistant but now, after being widely planted, are susceptible to apple scab.
Rosy-pink and red flowering crabapples didn’t come about until the ‘Niedzwetzkyana’ apple with purple foliage and rosy purple flowers was brought from what is now Kazakhstan in 1897 by Niels Hansen of the South Dakota Ag Experiment Station. He crossed these with hardy Siberian crabapples and created “rosybloom” crabapples that revolutionized ornamental flowering crabs. The first introduction was ‘Hopa’ in 1920. The University of Minnesota released “improvements” including ‘Radiant’ in 1957. Rosybloom crabapples are susceptible to foliage diseases and often leafless by late summer though they are spectacular in bloom. They are a historic component to the Arboretum’s crabapple collection.
Crabapples most popular ornamental appeal are their flowers which may be white, pink or rosy red to purplish red. The fruit are actually much longer lasting and of greatest ornamental appeal for the landscape. In selecting a crabapple for the landscape, one should think first about a tree’s fruit size, color and persistence. Most traditional landscapes don’t want the varieties that drop fruit. Most crabapples bear fruit every year but some older varieties bear alternate years. The crabapple tree’s ultimate size, shape/or form is also important when selecting a crabapple. Newer cultivars are compact, upright (columnar, vase or fan shaped), spreading or weeping.
The Arboretum’s Crabapple Collection includes 138 taxa (cultivars, species and subspecies). It includes historic cultivars from the Arboretum’s beginning, some trees dating to 1958. The current Arboretum’s crabapple collections intent is to showcase disease resistant selections suitable for our Upper Midwest climate. 16 new varieties were planted in the spring of 2018.
Crabapples rate very high in wildlife value from pollinators and beneficial insects, and as host to many insects that feed the food chain as well as providing food from their fruit, especially important for winter to early spring. All have “edible” fruit, but some better for culinary use.