How to Grow and Care for Flowering Crabapple

Within the large Malus genus, which also includes the species grown for large table apples, there are more than 30 species that feature smaller tart fruits and magnificent flowers. These are the flowering crabapples, of which there are many dozens of named cultivars. Many of these are grafted types, produced by joining the branch cuttings of more ornamental species onto rootstocks of hardier Malus species. These small to medium-sized trees are extremely popular for their fragrant, delicate spring blossoms. Crabapple trees are normally planted from potted nursery specimens in the fall. They have a moderate growth rate of 12 to 24 inches per year, and a 5-gallon potted tree may take three to five years or even longer before it flowers heavily.

Like all apples, crabapples have seeds with trace amounts of amygdalin, a substance that breaks down into cyanide. However, large numbers of seeds must be chewed and swallowed to have a serious impact. Since crabapples are generally sour and unpalatable to humans, there is little chance that many seeds will be digested.

Flowering Crabapple Care

Select a location with plenty of sun, not too close to a foundation, and a good distance away from other large trees. Follow general rules for tree planting: Loosen the root ball gently, use soil amendments (peat moss and coffee grounds both help keep soil slightly acidic), dig the hole twice as large as the root ball, and water frequently and deeply during the first few weeks.

Regular pruning and frequent evaluation for disease and pest problems are essential for growing a long-lived tree. These are relatively high-maintenance trees.

Light

If you have other trees on your property, make sure the crabapple is not too shaded, will as it needs at least six hours of sun a day to guarantee ample blossoming and fruiting. Some cultivars can tolerate a partial shade location.

Soil

When planting, be sure to add plenty of organic soil amendments to give your tree roots a good start. Rich soil with good drainage is ideal, and they prefer a slightly acidic soil pH.

Crabapples do well with natural mulch. If turf lawns surround them, this can make the tree somewhat more susceptible to fungus or pests. Mulch also helps to keep the roots cool and moist in summer if a heatwave arrives.

Water

Once established, your crabapple tree should not need extra watering unless there is an exceptionally dry season. They tend to be drought-tolerant, but if the rainfall for your area is particularly low, give your tree a deep watering at the base of the tree, in the morning or evening once a week, to keep it healthy. About 1 inch of water per week, through a combination of rainfall and irrigation, is ideal for these trees.

Excessive rainfall can harm the tree's growth cycle and productivity. You can place a tarp or other barrier over the tree's roots during rainy periods to keep the soil from getting too soggy.

Temperature and Humidity

Crabapple trees are best suited for regions with cold winters and warm but not stifling summers—the typical climate in USDA zones 4 to 8. There are a few cultivars that can tolerate zone 3 cold and some that can be coaxed into surviving in zone 9. But most crabapple trees require an extended winter period at 45 degrees Fahrenheit or less, so they are not good choices for most warm climates.

When high humidity (above 60 percent) is combined with prolonged temps above 70 degrees Fahrenheit, fungal and bacterial diseases are notable problems.

Fertilizer

Most apple trees don't need much in the way of fertilizer. A good rule of thumb is to put a small amount of compost around the tree's roots in the spring and a light application of composted manure in the late fall. Using natural mulch (wood chips or pine bark) can help keep nutrient-rich soil intact.

Types of Flowering Crabapple

There are many crabapple cultivars, and they can vary dramatically in size, form, hardiness, fruit production, and bloom color. Much of the breeding work in recent years has been in developing cultivars that are resistant to the common diseases that plague crabapples, such as fireblight and scab. Some of the more popular cultivars include:

• 'Prairifire' has a rounded, upright habit, dark pink flowers, reddish-brown leaves, and fruit that persists well into the winter. They typically grow to around 15 to 20 feet tall.
• 'Red Splendor' has a spreading, dense form, bright pink blooms, yellow fall leaves, and cherry-like and very persistent fruit. It is known for its cold hardiness and decent disease resistance.
• 'Beverly' has a rounded, dense form, white blooms, glossy red and retentive fruits, and yellow fall foliage. It is known for good disease resistance, particularly for apple scab.
• 'Adams' is a standard-sized crabapple with a broadly rounded shape and deep pink flowers. The crabapples are small and glossy red, and very attractive to birds.
• 'Abarina' is a small 10-foot tree with creamy white flowers. Avoid spring pruning, as this tree is somewhat susceptible to fireblight.
• 'Amerispirzam' is an 18-foot tree with deep rosy red flowers and clusters of glossy red crabapples.
• 'Adironkak' is an 18-foot tree with pure white flowers and orange-red fruits. It has an upright, columnar shape that makes it perfect for narrow spaces.
• 'Callaway' is known as a good crabapple for southern climates, as it has low chilling needs and is quite resistant to scab, fireblight, powdery mildew, and rust.
• 'Cinderella' is a dwarf 8-foot tree with white flowers and yellow fruits.
• 'Harvest Gold' is a fairly wide-spreading tree that makes a good small shade tree. Growing to 25 feet tall and wide, it has white blossoms and yellow fruits.
  

Pruning

All crabapple trees benefit from regular annual pruning. Dead branches, water sprouts, and smaller new growth can be trimmed at any time, but you may want to wait until after blossom season. If you want to prune branches larger than 1 inch in diameter, it's best to wait until late fall and use a pruning saw. Pruning during the active growing season can open the tree up to bacteria and insect damage.

An old adage regarding applet tree pruning says you should be able to throw a cat through the branches without hitting any of them. Kindness to cats notwithstanding, this kind of spacious pruning practice allows for good air circulation, which helps reduce disease risks.

Never prune away more than about 20 percent of a tree's canopy in a single season; with a neglected tree, you should gradually prune it back into shape over the course of several years. Branches that are crossed, or heading in that direction, should be pruned away. The more sunlight that reaches into the center of the tree, the more blooms the tree will produce.

Applewood is fragrant when burned and can also be used for barbecue cooking or smoking to impart flavor.

Propagating Flowering Crabapples

Most named crabapple cultivars are grafted trees, produced by skilled nursery professionals who meld branches from ornamental varieties onto hardier rootstocks. Such a procedure is not practical for most amateurs. While it is certainly possible to take softwood cuttings from your crabapple tree, root them, and grow them into trees, the resulting specimen may not have the hardiness or performance of the parent tree.

The exception to this rule is if you happen to have a pure ungrafted crabapple species, such as Malus floribunda (Japanese crabapple) or Malus mandshurica (Siberian crabapple). If you wish to try propagating your crabapple tree from cuttings, here's how to do it:

1. During the early growing season, use sharp pruners to clip 8- to 12-inch cuttings from flexible green growth at the tip of the crabapple's branches.
2. Strip off the lower leaves, then use a sharp knife to scrape off the bark on the bottom 3 inches of the cuttings.
3. Dip the stripped end in rooting hormone, then plant each cutting in a pot filled with moist, coarse sand.
4. Place the cutting in a loosely secured plastic bag to hold in moisture, then set the pot in a sunny location. Keep the cutting moist until roots form, which generally takes about 4 weeks. Check periodically to add moisture, if necessary.
5. When roots have developed, remove the plastic bag and continue to grow the cutting in full sunlight. After another few weeks, you can transplant the sapling into a larger container filled with commercial potting soil.
6. Continue growing the tree in the pot until it is large enough to transplant into the garden. A cutting started in spring should be ready to plant in the garden by fall.

How to Grow Flowering Crabapple From Seeds

Because most named crabapple cultivars are grafted plants, propagating by seeds collected from the fruit usually does not produce a plant with the same hardiness and disease resistance as your parent tree. However, if you wish to try it, collect some seeds from fruits that are fully ripened and dried. If the seeds are collected in fall, it's generally best to store them through the first part of the winter and start them indoors in late winter.

Plant the seeds in small pots filled with a mixture of commercial potting soil, peat moss, and perlite or vermiculite. Press the seeds down into the potting mix and cover them with a bare covering of additional potting mix. Moisten the pots and set them in a right, warm spot. Cover the pots with a plastic cover. When the seeds germinate and sprout, remove the plastic cover and continue growing them, making sure the potting mix remains moist.

When the seedlings are about 6 inches tall, transplant them into larger containers filled with commercial potting mix. Pinch back the tops to encourage side branching. When the seedlings reach a height of about 18 inches, they can be acclimated to outdoor conditions for a week or two, then planted in the garden.

Overwintering

Within its hardiness range, a crabapple tree generally requires no winter protection, though you may want to shield the trunks of young trees with metal hardware cloth or fencing to prevent damage from rabbits or deer. Young trees can be susceptible to winter sunburn, and the trunks should be wrapped with a commercial-grade tree wrap for their first few years.

The ground beneath a crabapple should be raked clean of leaf and fruit debris before winter sets in, to prevent fungi and insect larvae from overwintering. A thin layer of well-decomposed manure applied in late fall will help enrich the soil for the following spring.

Common Pests and Plant Diseases

Like other apples in the Malus genus, crabapples are quite susceptible to several diseases, including:

• Fireblight is caused by the Erwinia amylovora bacterium. Its symptoms are oozing wounds in the tree's bark and blackened, burned-looking leaves. Good sanitation is key to preventing the spread of the disease, for which there is no cure. Make sure to plant cultivars that are resistant to fireblight, and avoid fertilizing with high-nitrogen fertilizers on lawn areas beneath the tree, which can encourage the bacteria.
• Rust is caused by several different fungi that cause orange-yellow spots on the leaves. Mild disease usually doesn't require treatment, but fungicides can be used on severely diseased trees.
• Apple scab is a fungal disease that causes olive-black spots on the leaves and fruits of the tree. Symptoms usually begin in May or early June. Infection is hastened by prolonged wet weather and sometimes will completely defoliate the tree by late June. Keeping ground areas well-tended can prevent the fungi from overwintering. Properly timed application of fungicide can also help treat the disease.
• Powdery mildew is a fungal disease that causes a coating of grayish-white powder to cover leaves. Though unattractive, powdery mildew usually does no lasting harm. Regular pruning to improve air circulation often helps prevent powdery mildew.

These are the most common insect pests:

• Mites are most often identified by the reddish appearance created on the twigs, followed by withering leaves. Smothering the insects and eggs with horticultural oil is the best remedy.
• Aphids are tiny insects that feed on leaf juices. They are most often identified by the sooty black mold that grows on the sticky honeydew excretions left by the insects. Spraying with horticultural soaps or oils is an effective treatment.
• Japanese beetles chew holes between the veins of leaves, often giving them a skeletonized look. While carbaryl insecticide will kill beetles, its use often encourages intense mite infestations, so it's best to ignore Japanese beetle damage unless it is very severe. Beetle infestations are cyclical, and populations do not necessarily persist year after year.
• Appletree borer is the larval stage of the Chrysobothris femorata beetle. These worms often attack young or sickly trees, boring into the trunk and main branches. Cracks may appear in the bark of the tree. Eventually, the damage can girdle the limb or trunk, killing major branches or the entire tree. There is no control for this pest, other than keeping your tree healthy so it can fight off the damage.

How to Get a Flowering Crabapple to Bloom

There are a number of reasons why a crabapple tree might fail to bloom:

• Tree is too young: A crabapple tree often takes three or four years before it is mature enough to bloom and bear fruit. Be patient with a young tree.
• Weather patterns: A fall that is too dry may prevent a crabapple tree from blooming the following spring. If late summer and fall weather is especially dry, make sure to keep your tree well-watered. Similarly, late frost in the spring can sometimes kill flower buds for that season. If your winter was too mild, the tree may not have received the prolonged time at sub-45 degree temperatures necessary to promote budding. Once weather patterns normalize, your tree should return to a normal flowering pattern.
• Not enough sun: If surrounding shade trees have grown up to block the sun, your crabapple may respond by withholding flowers. A tree that is badly overgrown will shade its own inner branches, which can also limit flowering.
• Disease: Look for signs of fireblight or fungal diseases. Sickly trees will not flower as robustly.
• Severe pruning: A neglected tree that was pruned too hard may not flower the following spring. This is not a cause for concern, as it will probably return to healthy blooming after a year off.
  

Common Problems with Flowering Crabapple

Flowering crabapples are prone to almost as many complaints as they are compliments. In addition to the many disease and pest issues already described, homeowners often express these concerns:

Cracked, Oozing Bark

Unfortunately, these all-too-common signs on a flowering crabapple can point to a number of serious pest and disease issues, including fireblight or apple borers. Make every effort to keep your tree healthy and treat the problems that are diagnosed. It's best to have a professional look at your tree and make recommendations for how to treat it.

Lots of Dead Branches

While it's possible that dead branches are signs of insect or disease, it's more often caused simply by neglect of the annual pruning routine that is necessary to keep a crabapple tree looking its best. Faced with a ragged-looking tree, establish a three-year plan to gradually restore the tree to its healthy state.

Wasps Swarm Around Tree

Fallen rotting fruit beneath an apple tree is an invitation to yellow jackets and other stinging wasps, who love to feed on the sweet juices. As the tree begins to shed ripe fruit, make sure to routinely rake the ground to remove debris.