Rose family (Rosaceae)
Description: This small tree is 15-25' tall at maturity. It has a short trunk that is often crooked and a broad irregular crown. The trunk bark is variable, but it is often reddish gray-brown, rough-textured, and covered with longitudinal scales that often curve. Sometimes the trunk bark is more flat and less developed. The bark of branches is reddish brown or dark reddish gray and smooth. Along the larger branches, thorny side branches often develop. The blades of the alternate leaves are 1½-3" long and ¾-2" across; they are more or less ovate, coarsely toothed, and often shallowly cleft. The upper blade surface is yellowish green to bright green and hairless, while the lower surface is pale green and hairless (or nearly so, except for very young leaves). The slender petioles are ¾-2" long, light green to bright red (often the latter), and hairless to nearly hairless.
Cymes of 2-6 flowers are produced from short spur-like branches. Individual flowers are 1-1¾" across, consisting of 5 pink petals (often becoming white with age), a green to reddish green calyx with 5 narrowly triangular lobes, a pistil with 5 styles, and 10-20 stamens. The exterior surface of the calyx (facing away from the petals) is smooth and hairless, while its interior surface is densely covered with appressed silky hairs. The slender pedicels are 1-2" long and hairless to nearly hairless. The blooming period occurs from mid- to late spring and lasts about 2 weeks. The flowers have a pleasant fragrance. Fertile flowers are replaced by a globoid fruit (pome) that is ¾-1½" across. The fragrant fruit is initially green, but it later becomes yellowish green or yellow at maturity; its surface is smooth and waxy. The hard flesh of the mature fruit is slightly juicy and sour-tasting; it contains several seeds toward the center of its interior. The root system is woody and branching, sometimes producing underground runners that form clonal offsets.
Cultivation: The preference is full or partial sun, moist to dry-mesic conditions, and soil containing loam or clay-loam. This small tree is vulnerable to a variety of insect pests and foliar disease organisms. It should not be planted near Juniperus virginiana (Red Cedar), which can spread cedar-apple rust.
Range & Habitat: The native Wild Crab Apple is occasional in southern Illinois and uncommon or absent in the central and northern sections of the state (see Distribution Map). Habitats include open woodlands, woodland openings, woodland borders, savannas, and thickets. Wild Crab Apple can be found in both upland and bottomland areas where other deciduous shrubs and trees are present, particularly where there has been some disturbance to reduce the overhead canopy of dominant trees.
Faunal Associations: The flowers are cross-pollinated by honeybees, bumblebees, long-horned bees (Synhalonia spp.), and other long-tongued bees. Other floral visitors include small short-tonged bees (Andrenid, Halictid), butterflies, and skippers. These insects obtain nectar from the flowers, although some of the bees may collect pollen. Like other Malus spp., Wild Crab Apple attracts its fair share of insect pests. The caterpillars of many moths feed on the leaves and other parts of this small tree (see Moth Table). The caterpillars of the butterflies Limenitis archippus (Viceroy), Limenitis arthemis astyanax (Red-Spotted Purple), Papilio glaucus (Tiger Swallowtail), and Satyrium liparops strigosum (Striped Hairstreak) also feed on the leaves. Beetles and weevils that feed on Malus spp. include Rynchaenus pallicarnis (Apple Flea Weevil), Anthonomus quadrigibbus (Apple Curculio), Conotrachelus nenuphar (Plum Curculio), Macrodactylus subspinosus (Rose Chafer), Popillia japonica (Japanese Beetle), Saperda candida (Round-Headed Apple Tree Borer), Saperda cretata (Spotted Apple Tree Borer), Agrilus vittaticollis (Apple Root Borer), Chrysobothris femorata (Flat-Headed Apple Tree Borer), Monarthrum mali (Apple Wood Stainer), Amphicerus bicaudatus (Apple Twig Borer), and Paria fragariae (Strawberry Root Worm).
Other insects feeders include aphids, leafhoppers, treehoppers, and other insects (see Insect Table). Among vertebrate animals, many upland gamebirds and songbirds occasionally eat the fruit (see Bird Table), as do such mammals as the Black Bear, Gray Fox, Red Fox, Opossum, Raccoon, Striped Skunk, Fox Squirrel, Gray Squirrel, Meadow Vole, and Deer Mouse. Cottontail Rabbits browse on the foliage and twigs of young saplings during the summer, and gnaw on the bark of older trees during the winter. White-Tailed Deer also browse on the twigs and foliage. Because it is densely branched and thorny, Wild Crab Apple provides nesting habitat and cover for the Yellow-Breasted Chat, Song Sparrow, Orchard Oriole, and other birds.
Photographic Location: A thicket near the Maumee River in NW Ohio.
Comments: Other common names of Malus coronaria are American Crab Apple and Sweet Crab Apple. The latter name probably refers to the fragrance of the flowers or fruit, rather than the taste of the fruit, which is sour. This small tree is quite attractive during the spring when its relatively large flowers are in bloom. There is a narrow-leaved variant of Wild Crab Apple, Malus coronaria dasycarpa, that can be found in southern Illinois. Another native species, Malus ioensis (Prairie Crab Apple), differs from Wild Crab Apple by having leaf undersides, petioles, pedicels, and calyx exteriors that are conspicuously hairy. Most cultivated apples and crab apples can be distinguished from the preceding native crab apples by the lack of thorns on their branches and lack of cleft lobes on their leaves. Many of these cultivated species have originated from Eurasia or East Asia, and they occasionally escape into both disturbed and natural areas, especially around suburbs and cities.