Crab apples and Apples are the same species, but different cultivars. An apple that's over 2 inches round is considered an apple, while anything smaller is a crab apple. They are both edible, although crab apples got a bad rep due to the bitter and pithy taste of ornamental varieties commonly grown.
Contrary to urban legends and old wives tales crab apples are not toxic. Like apples, they do contain a natural form of cyanide, primarily in their seeds, but in order for these minute trace amounts to have any effect, you'd have to consume a few hundred pounds of crab apples, seeds and all.
Most crab apples are also more acidic than standard apples and have elevated levels of pectin. This makes them excellent for preserves and even pickling.
Crab apple trees generally require pollen from another apple or crab apple tree to ensure fruit production, there are a few exceptions. Among edible crab apples Wickson, Chestnut and Whitney will produce fruit with only one tree.
Edible Crab Apple Varieties
1. Butterball Crab Apple is used largely as an ornamental but it does have edible qualities. It is self pollinating however pollination by another apple variety will maximize the yield. Pink blossoms drown out the delicate pale green foliage in spring and give way to golden yellow fruits with occasional hints of red orange blushes in summer and early autumn. It produces such an abundance of fruit that the tree is weighed down and droops from the burgeoning weight.
Butterball works exceptionally well as a pollinator for all apple varieties not only due to its abundance of flowers, but the long duration of its flowering which goes on through out the pollination season. Butterball can be eaten fresh, it is like eating a crunchy lime, yes - it is a tad sour. It is best used for preserves and pastries where it works well due its high pectin content.
2. Centennial Crab apple produces high quality fruit that is delicious fresh off the tree. It reaches 8 to 15 feet in height. Sometimes used as a pollinator for other apple trees. The crab apples are a fiery Orange Red with a moist and juicy white flesh.
3. Chestnut Crab apple is frequently used as a pollinator for other apples. It is also one of the few cultivars that is self pollinating. Introduced by the University of Minnesota in 1946, the 15 to 20 foot trees produce a yellow crab apple with red highlights, some say a red crab apple with yellow blushes. The crisp flesh is sweet with an earthy nut like flavor.
4. Dolgo aka Dalgo crab apple serves well as an ornamental and edible fruit producing tree. It is fairly large as crab apple trees go reaching over 30 feet in height at times. Good resistance to scab and fire-blight. It is frequently paired with other fruits in preserves and sauces.
5. Hopa Crab apple is an old heirloom variety that reaches 20 to 25 feet in height. It produces aesthetically appealing blushes of pink flowers and delectable red fruits in early Autumn. Also produces a vivid fall foliage as its dark green leaves turn a vibrant yellow. These apples can be eaten fresh but work best in preserves. Being an older variety it is more susceptible to disease than young whipper snapper hybrids.
6. Pink Spires reaches 12 to 15 feet. It's a Columnar Fruit Tree that grows very narrow and upright, making it an awesome addition to a patio or confined yard space. Spring Flowers are rosy pink and appear earlier than most varieties. Purplish red fruit is ripe by early September into October. The foliage is perhaps the reason this cultivar is so popular in the spring it has Leaves have a purple tinge that offsets the rosy pink blooms. The fruit is very small, sometimes berry sized and will hang on the tree into midwinter if left unharvested. Edible fresh or for preserving.
7. Prairie Fire is another relatively new variety that can reach up to 20 feet in height but averages around 12 -15. It's foliage is strikingly maroon to dark lavender, come Autumn it morphs to variant shades of auburn, orange and red. The biggest detraction from this cultivar is that although the fruit is edible, basically it sucks and is best left for the birds and tree rats. Not even good for preserves. It is classified as an edible crab apple but is more suited for ornamental purposes.
8. Red Vein crab apples are a tad larger than most varieties of crab apple, they are roughly 1 inch round. They have a wider range than many of their cousins being suited for USDA zones 4 to 10. The coloration of Red Veins is unique as it produces fruit in varying shades of red from ruby red to pinks and even golden. The pulpy flesh also varies in color with variegated striations of red and magenta running through it. They are acidicly juicy and crisp, if you like a tart fruit this is one you will enjoy. Most people however use it for preserves and sauces, blended in with other apples it adds a nice accent to apple butters and apple sauce.
9. Rescue Crab apple is hardy as far North as USDA Zone 2 , that is averaging 10 to 20 degrees below zero in the dead of winter. It is also suitable for the deep south, in essence it is a very adaptable and versatile tree. Produces attractive white flowers prolifically in the spring which give way to clusters of sweet crab apples. This hybrid does not have the acidity or tartness associated with most crab apples. The only drawback I noticed so far as taste is concerned is that they are not as crisp as you would expect with a fresh apple. In fact once they hit tehir peak they degrade quickly, so harvesting just before they ripen fully is best in my opinion.
10. Sweet crab apple aka garland crab apple reaches 20 to 25 feet in height. Flowers appear in late spring starting as pink buds and morphing into white flowers sometimes with a hint of rosy pink. The fruit is a yellowish green when young and turn reddish when ripe. The apples grow in clusters and commonly cling to the tree well into winter. Can be eaten fresh, but unlike ts name it is more tart than sweet, if you like to pucker up go for it. Excellent for preserves, jellies, sauces and even cider.
11. Whitney Crab Apple reaches 14 to 16 feet in height. It produces sweet crab apples suitable for preserving and cooking and is not unpleasant when devoured fresh. It flowers in pink and white in spring and produces fruit by mid summer. It is one of the few crab apples that is self pollinating. It is tolerant to temperature extremes, and has more disease resistance than many of the older varieties.
12. Wickson Crab apple is the result of cross breeding of Spitzenberg crab and Newton crab apple varieties. Wickson, like most hybrid crab apple varieties is highly disease resistant and hardy. It does not however resemble other crab apples so far as taste is concerned as it is very sweet and simultaneously acidic, basically a hardy robust apple flavor with a touch of tartness. It is great for eating fresh or preserving and is prized by some 'apple connoisseurs' for cider making as well as pie, [pastries and preserves. It is also larger than the bulk of crab apples averaging about 1.5 inches in diameter. The fruits color ranges from pale yellow to a bright cherry red and at times a variegated meld of the two.