If you have a sunny site in your yard and want to grow crabapples, propagate your own from the seeds or cuttings of an existing healthy crabapple. Wild crabapples produce numerous shoots and suckers that are easily propagated, and if you have the time and patience, you can even grow them from seed. Crabapples are gorgeous in the spring, covered with beautiful blossoms, and will produce a heavy crop of small, tasty apples in the fall.
Choose a sunny site outdoors and loosen the soil down to about 10 inches. Add potting soil or rich compost, then shove a pencil or the handle of a wooden spoon down into the soil about 6 inches to create a planting hole. You can also prepare containers if not planting directly outdoors.
Take cuttings of green crabapple wood, 7 to 9 inches long, from the ends of young branches, using a very sharp knife or pruners dipped in alcohol or a bleach solution. Strip off all the leaves from your cutting, except for two or three at the tip of the stem. Dip the cut end into a container of rooting hormone, shake off the excess, and plant the cutting in the prepared spot. Keep the soil moist but not wet --- rooting will take at least two months.
Dig around shoots or suckers to uncover the roots, cut them, and plant them outdoors or in containers. According to Ron Smith with the North Dakota State Extension Service, you can also nick older roots that may produce new shoots. Use a plant growth regulator (PGR) high in cytokinnins and low in auxins (both plant hormones) to help with shoot development. You can "stool" the new shoots after they're nicked by mounding up potting soil or compost around the base of the shoots.
Remove crabapple suckers in early spring before new growth is under way. Prune the branches if necessary, but don't remove more than 25 per cent of the branches each year. Excessive pruning will cause increased sucker growth.
Consult your local extension service if you find numerous little holes in the bark of your crabapple; you may have borers or bark beetles. Crabapples are also susceptible to "apple scab," a fungal plant disease that will cause crabapple leaves to drop in the summer. Clean up and remove all the fallen leaves and fruit in the fall, and spray in the spring with lime-sulphur before the tree buds out and again after it's fully leafed out. Captan is a recommended fungicide for treating scab.
Crabapples often exhibit peeling bark as they get older; this is normal. Prune crabapples before growth begins in the spring. Don't prune more than 25 per cent of the tree each year. Young crabapple trees need five or six years of growth before they bloom; it takes about five to six years for young trees to grow up enough to produce flowers. Do not fertilise crabapples at the base with turf fertiliser; this causes excessive leaf growth and will reduce flowering and thus fruiting. Crabapples make wonderful jelly and applesauce; wait until after the first frost for peak flavour. Good crabapple varieties for jelly include Dolgo, Centennial, and Chestnut.
According to Purdue University, crabapples grafted onto rootstocks of other crabapples cannot be propagated from seed or cuttings.