When & How to Perform a Heavy Pruning
Do your major pruning during the dormant season. The ideal time to prune a crabapple tree is late winter or early spring, before the new set of leaves begin to appear. It is possible to prune in mid- or early winter, as well, though this may make the tree more vulnerable to cold-related injury. Hold off on pruning your crabapple tree until after the first killing frost of the season to ensure that it has gone dormant. In a pinch, it’s okay to prune in early summer after the tree has finished blooming, although this can increase the risk of fire blight and other warm-weather diseases. Aim to have your pruning finished before June (or December, if you’re located in the Southern hemisphere).
Use a pruning saw or chainsaw to prune thick branches. One of these tools will make it easier to cut through large stems. Chainsaws offer more power for quick and easy trimming, while handheld pruning saws allow for greater control so you’ll only take off as much unwanted growth as you need. It may also help to have a pair of telescoping loppers to remove smaller stems and offshoots high up in the canopy of the tree.
Cut large limbs where they connect to the trunk. Start by notching the underside of the targeted branch 4–5 inches (10–13 cm) from where it meets the trunk. Then, make a second cut 2–3 inches (5.1–7.6 cm) further out on the limb, this time sawing all the way through. Go back and remove the remaining stump at the collar, or the thick section where the branch grows out of the trunk. The first undercut you make will prevent excess bark from peeling off the trunk once the limb comes free. Avoid cutting perfectly flush with the trunk. Insects and disease-causing organisms can easily find their way into the tree through open wounds in the trunk.
Clear out dead or dying wood first. Inspect the tree for branches that are rotting or appear brittle and colorless. When you find an affected branch, remove the entire limb at its collar. If you’re unsure whether a branch is dead, scrape the wood with your fingernail to remove a portion of the bark. If the flesh underneath is green-white, it’s still alive. If it’s brown or black, it’s most likely dead. Keep your crabapple tree free of dead wood all throughout the year, not just during pruning. Dead wood is more likely to introduce disease.
Cut away inward-growing branches. Occasionally, a branch will begin to twist in on itself as it grows, reaching back toward the center of the tree rather than out away from the trunk. Saw these branches off as close to the collar as you can without accidentally cutting into the trunk itself or other nearby branches. Removing inward-growing branches will give the tree a neater, more uniform shape.
Trim branches that cross or are growing too close together. Similar to inward-growing branches, it’s possible for some branches to become entwined or compete for space. To get rid of branches that are already crossing, take off both branches where they connect to the trunk. For branches that are growing close together but not yet crossing, remove the weaker or more awkwardly placed branch.
Thin out the lower branches if desired. Low-hanging branches sometimes interfere with walking, mowing, or other activities that require you to pass beneath the tree. If this is the case, saw them off as close to the trunk as possible, as you would with any other large branches. Remember to make your cuts as clean as possible so that no stumps remain. If your tree’s lower branches aren’t causing a problem, it’s usually best to let them stay.
Keeping Your Crabapple Tree Healthy
Remove basal suckers with shears. Suckers are spindly, invasive branches that grow underground and sprout around the bases of mature trees. Most suckers are thin and weak enough to remove using a pair of gardening shears. Clip the suckers down low, at the exact point where they emerge from the ground. Basal suckers most often originate at the rootstock that the crabapple was grafted onto. If left alone, these tiny branches can develop into whole new trees, complete with different flowers and fruits. Removing suckers as soon as you spot them will redirect energy to the parts of the crabapple tree you want to preserve.
Snip off emerging water sprouts. Water sprouts are slender shoots that grow vertically out of the main branches of the tree. Like basal suckers, snip water sprouts with a pair of sharp gardening shears where they emerge from the branch. Try to catch emerging water sprouts when they’re still young and green. At this stage, you’ll be able to simply pull them off by hand, which makes it harder for a new one to grow in its place. Too many of these undesirable shoots can crowd out the other branches and reduce airflow within the tree, leading to disease, rot, infestations, and other complications.
Keep aesthetic pruning to a minimum. Many arborists are tempted to spur their crabapples to grow by continually pruning their live branches. However, this can be risky, as over-pruning can backfire and trigger an explosion of water sprout growth. If you want to shape up your tree, restrict yourself to a few scattered cuts, thinning out smaller branches all the way back to the parent stem. The tree’s upper crown is especially likely to produce an overabundance of water sprouts if cut back too much. Never remove more than ⅓ of your crabapple tree’s total live growth in one year. Doing so could severely stunt its growth or even kill it.
Eliminate entire sections of the tree that are infected with fire blight. Fire blight is a bacterial infection that’s common in crabapples, especially after pruning. If you encounter growth that’s suffering from fire blight, remove the diseased branch along with the parent stem it’s growing from. Dispose of both parts in a leaf bag or similar container and thoroughly disinfect your tools afterwards. Trees affected by fire blight typically have branches that appear burnt or blackened and may produce shriveled, “mummified” fruit. If you notice fire blight on a major limb, you may be able to save it. Try scraping off the outer layer of bark all the way down to the healthy tissue underneath to ensure that the disease doesn’t spread.
Remove any other diseased wood you come across. In addition to fire blight, crabapples are also susceptible to other common plant diseases like scabs, rust, and powdery mildew. Branches showing signs of disease should be cut at the collars and disposed of or discarded a safe distance away from the rest of the tree. Always disinfect your gardening tools thoroughly to prevent disease from spreading from one part of the tree to another. The simplest way to do this is to dip the blades in rubbing alcohol before making a new cut. If the trunk or root system of the tree appears to be infected, it may be too late to save it.
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