Flowering Crabapples (Malus spp.) are common small ornamental trees in the Rose family. These should not be confused with the large-fruited eating apples grown in orchards. Some species are native to North America, but many have come from Europe and Asia. Flowering Crabapples are popular due to their colorful flower, leaf and fruit displays. Their fruits provide an important food source for birds and mammals, although fruits can be messy. There are hundreds of hybrids so exact identification can be difficult.
Many crabapples are riddled with pest issues (chewing caterpillars, rust, scab, and powdery mildew are common) and at some point in the growing season, many trees tend to look ratty and unhealthy. Caring for crabapples usually involves tending to their pest susceptibilities and smart applications of pesticides. Crabapples flower and fruit best if grown in full sun, otherwise too much shade or wet conditions aggravate disease. They have little need for pruning and it is usually done to remove cracked and dead branches or to manage disease. The ideal time of year to prune crabapples is late winter when diseases have slowed and plant defenses are strongest. Pruning should be kept minimal because heavy-handed pruning ALWAYS will respond with prolific sucker/shoot growth.
You will be most successful with a crabapple if you choose a disease-resistant variety, plant in a good location, stay on top of pest issues before they get out of control, and only prune lightly.
The short answer is NO. Many people have seen or heard of wound sealants and wonder if they should be using them for the tree’s health. The tree care industry has done a 180 on this topic, from advocating to discouraging their use, which has confused many. This was a common practice decades ago; old tree care texts recommended it and sealant products are still sold at many garden centers. Many substances had been used from roofing tar to latex house paints. It was believed that using these on trees kept out fungi after a cut exposed its vascular tissues.
Research has since shown that tree cuts need open air to trigger natural wound sealing properties. Trees contain chemicals that inhibit fungi and resist decay in the area where a branch meets the main trunk. This area, called the branch collar, is where we are supposed to make our final pruning cut when removing a branch for this very reason. Therefore, the best way to guard against fungi and decay development is to make accurate and judicious cuts and let them breathe.
Deciding when to prune/trim is confusing to many people because there is no one-size-fits-all answer and even the experts can’t always agree. Yet, it is the most commonly asked question of gardeners, landscapers and arborists! Pruning of live branches is not as critical as many people think, but it is worthy of discussion.
The Best Times for Pruning: (the opposite of Part 1; Worst Times)
In general, the optimal times for ornamental tree and shrub trimming is early spring and summer and those should be the go-to times if you are unsure. Don’t let timing keep you from grabbing your pruners if a haircut is truly needed and you just can’t wait!
If you are trying to figure out the best time to prune/trim, start first with the worst times to prune (because more experts agree on these) and work backwards from there.
So, what are the worst case scenarios in pruning at the ‘wrong time’?
One important point is that pruning at the “wrong” time of year probably won’t kill your tree or shrub, but it may weaken it in the long run. Indeed many plants are trimmed at less than ideal times and yet they survive.
The Worst Times for Pruning:
To be continued in When To Trim, Part 2.