Jennifer Schultz Nelson
Extension Educator, Horticulture
The crabapple is a tree highly valued for its springtime flowers, small to medium growth habit, and its fruit. This time of year, the crabapple grabs the spotlight with its spectacular flower display.
There are about 35 different species of crabapple in the world. They are sometimes commonly referred to as "wild apples". There are an additional 20 or so domesticated apple species, from which we harvest their fruit, the apple.
Crabapples are great specimen trees for the landscape because of their relatively small stature of 10 to 25 feet depending on the cultivar, and their moderate growth rate of eight to ten inches per year. They are a good choice for planting near utility lines because of their relatively small size. Bonsai enthusiasts also love crabapple for its naturally small stature, and small fruits.
Typically a mature crabapple develops a dense crown of twiggy branches. In the spring, those branches bear thousands of five petaled, white, pink, or red flowers, depending on the cultivar.
The flowers are perfect, botanically speaking. This means they contain both the male stamens and the female pistil. However, the flowers cannot pollinate themselves. They are self-sterile. All apples, including crabapple, depend on insects, especially bees, to act as pollinators and cross pollinate between different apple species and cultivars.
Different species and cultivars of crabapple and domesticated apples hybridize freely. So crabapples have been important historically for use as a source of pollen in apple orchards. It is not uncommon to see crabapples planted periodically amid eating apples in an orchard.
Sometimes growers even graft a crabapple branch onto an apple tree. As a temporary fix, growers may place bouquets of blooming crabapple branches near beehives to try and entice the bees into grabbing some crabapple pollen before they head to the main orchard.
This also means that if you want to grow apples in your home landscape, you don't necessarily need to plant more than one cultivar for cross pollination. If there is a crabapple tree in the neighborhood, it can serve as a source of pollen for your tree.
The fruit of crabapple is typically much smaller than the apples we routinely eat. They are usually red, but there are some yellow-fruited cultivars. They may be marble to golf ball sized. They are also extremely sour, and in some species they also have a woody texture. Crabapples are not an apple you would want to pick up and eat raw.
However, they are a rich source of pectin, and can be cooked and sweetened to make flavorful jelly, or other tasty treats. They may also be fermented and made into wine.
Depending on the cultivar, crabapple may or may not have good fall color. Some people have never seen their crabapple's fall color because of a fungal disease called apple scab.
Apple scab is a serious disease in both crab and domesticated apples caused by the fungus Venturia inaequalis. In this disease, fungal spots, or lesions, develop first on the undersides of leaves, and enlarge and spread. The fruits may also contract the fungus, and the lesions develop a scab-like appearance. The scabs are only skin deep, but they detract from the fruits appearance. In extreme infections the fruit may be deformed.
The fungus survives year to year in old leaves that are on the ground under the tree. The fungus produces spores that are released into the air in April, May and June. Wet, cool weather helps the fungal spores grow when they contact young leaves, flowers and fruits on the apple tree. The more rainy and cool the spring, the more likely that apple scab will be a problem.
Unfortunately, some older cultivars of crabapple are extremely susceptible to apple scab. In these extreme cases, the leaves become so heavily infected that they are distorted and even drop from the tree by midsummer. While this doesn't harm the tree to any great extent, most homeowners would agree that having bare trees in your yard during midsummer detracts from the landscape.
To control apple scab, good sanitation is one strategy. Rake the leaves that fall and destroy them. They are the source of fungal spores for the following spring. There are fungicides available to control apple scab, but they need to be applied at very specific times. Also, application may be an issue if your tree is very large. If you would like information on fungicides to control apple scab, contact my office.
The best (and easiest) method for controlling apple scab is to plant resistant varieties. A few crabapple varieties resistant to apple scab are: Anne E., Bob White, Molten Lava, Ormiston Roy, Prairiefire, Red Jewel, Sargent, Sentinel, Strawberry Parfait, and Sugar Thyme.
Prairiefire is one of my personal favorites, blooming an intense red-pink. Its flowers are striking, and groupings of more than one tree together are particularly beautiful. This cultivar was developed at the University of Illinois.
Saturday May 3rd, from 9 a.m. to 1 p.m. is the annual U of I Extension Master Gardener Plant Sale. The sale will take place at our office at 2535 Millikin Parkway, Decatur. This year the Master Gardeners have planned many new features for their sale.
There will be several popular named hosta cultivars offered, plus "grab bags" of hostas. A wide variety of annuals, perennials and herbs will be available, as well as a container garden workshop. There will be close to 50 different cultivars of tomato and pepper seedlings available, including heirlooms.
Master Gardeners will be on hand to offer their expertise. I will teach a grafting workshop at 10 and 11 a.m. using tropical hibiscus for $5. Graft your own hibiscus with multiple flower colors on each plant. There will also be a garden garage sale, and a bake sale sponsored by HCE. Join us for a morning of gardening fun!