Acer palmatum, commonly known as Japanese maple, is a gorgeous ornamental tree appreciated for its graceful form, leaf shapes, and fall colors. While Japanese maples require minimal overall maintenance, proper pruning is essential to keep them healthy and looking their best. In this article, we’ll discuss when and how to prune Acer palmatum correctly.
Why Prune Acer palmatum
Pruning serves several important purposes for Japanese maples
- Removes dead, damaged, or diseased branches
- Maintains an attractive shape and form
- Controls size and growth
- Allows light and air flow through the canopy
- Encourages healthy new growth
Japanese maples often look their best when left to grow naturally with minimal pruning. However, occasional judicious pruning helps sustain plant vigor and aesthetics.
When to Prune Acer palmatum
Timing is critical when pruning Japanese maples. They should only be pruned during their dormant season, between late fall and late winter. The optimal pruning window is November through March before sap starts rising and new growth emerges.
Pruning later in dormancy allows you to evaluate the plant’s form without leaves obscuring the branches. However, avoid pruning during below-freezing temperatures or extreme cold snaps.
Never prune Japanese maples during the growing season from spring to fall. Pruning at this time risks significant sap bleeding from the wounds, which can lead to disease and weaken or even kill the plant.
How to Prune Acer palmatum
Follow these tips when pruning your Japanese maple:
Use Clean, Sharp Tools
Use bypass hand pruners for smaller branches up to 1⁄4 inch diameter, loppers for those up to 2 inches, and pruning saws for larger branches. Sterilize tools before each use with a disinfectant like isopropyl alcohol to prevent spreading disease. Keep blades sharp for clean cuts that heal quickly.
Remove Damaged Growth
Inspect the plant and prune out all dead, dying, broken, or diseased wood. Also remove branches that cross or rub together.
Emphasize Natural Form
Japanese maples have an innate dome shape. When pruning for aesthetics, accentuate the plant’s natural form by selectively removing branches that disrupt the plant’s shape or growth pattern. Avoid shearing the plant into unnatural shapes.
Prune Lightly
Never remove more than 20-25% of the total foliage in one year, as excessive pruning can stress the plant. Take out only selected branches back to an appropriate lateral bud or branch.
Leave Lower Branches
Unlike some trees, Japanese maples should retain lower branches to maintain their natural shape. However, remove any branches with leaves that look different than the main canopy, which indicates undesirable rootstock growth.
Maintain Central Leader
Usually Japanese maples look best with one main central leader trunk and an open, tiered branch structure underneath. Remove competing secondary trunks and interior branches that could split the leader.
Stake Young Trees
Stake young maples for their first 1-2 years until well established. Attach ties loosely to allow some movement while preventing blowing over by wind.
Pruning Mature Acer palmatum
For mature Japanese maples, yearly light maintenance pruning is often sufficient after the tree’s initial structure is established. Minimal pruning preserves the plant’s natural form and vitality.
Focus on removing any dead or damaged branches, cleaning out the interior, and maintaining form with conservative trimming. Keep cuts clean just outside the branch collar without leaving stubs.
More extensive pruning is only needed periodically to reduce size or rejuvenate old plants. If major corrective pruning is required, take a gradual approach over 2-3 years. Never remove more than 30% of the canopy at once.
Weeping Varieties
Pruning for gracefully cascading weeping or laceleaf Japanese maples involves allowing a long central leader with branches trained horizontally. Tie down select branches to encourage the weeping habit. Remove any vertical shoots that disrupt the umbrella form.
While not an absolute requirement, regular pruning targeted at the right times of year will help keep your Acer palmatum healthy and looking its best. By following proper pruning techniques, you can maintain an attractive Japanese maple as a focal point in your landscape for years to come.
Fine Gardening Project Guides
Japanese maples are elegant in all seasons, with delicate leaves, fine fall color, and the loveliest branch patterns in the world. The two most common forms of this tree are the upright, understory tree (Acer palmatum and cvs.) and its little brother, the Japanese laceleaf maple (Acer palmatum var. dissectum and cvs.), a much smaller, weeping tree often used as a garden focal point. When planted in the sun, as opposed to a partly shaded understory, these trees become fully foliated rather than open and airy. Some simple pruning can restore or enhance their natural form, bringing the most out of them for summer and winter viewing.
Learn more: Potential Sources of Trouble for Your Japanese Maple
Japanese maples less than 15 years old are prone to put on new growth that looks like a buggy whip: unattractively skinny with no side branches. This problem is exacerbated by pruning, often done by the impatient tree owner hoping to create an open look sooner than nature intended. Shortening or removing the buggy whips only stimulates more of the same. My best advice is to leave the tree alone for as long as possible. You will be surprised to find that, as the whips age, they fatten up, develop lateral branches, and turn into nice-looking scaffold limbs. Trust me. Sit on your hands and wait to start the thinning process until after the tree has aged and developed some grace.
Another practice to avoid is attempting to restrict the height of a Japanese maple. It won’t work. The tree will simply grow faster with thin, unruly branches. The width of these trees, on the other hand, can be somewhat modified.
Further reading Enchanting Japanese Maples
The old gardener’s adage is “Prune when the shears are sharp”—and in general this is true. If you prune selectively, almost anytime is the right time to prune a Japanese maple. With that said, these maples are most easily pruned in winter or summer.
With the leaves out of the way in winter, it is easy to see the branch structure and, in turn, make the right cuts. In summer, however, you can judge the right amount of thinning needed to see the tree’s bones. Summer pruning also stimulates less plant growth than winter pruning, so you can get away with a little more and the tree will stay thinned out longer. I avoid pruning when the temperature is 80°F or higher, especially when the plant is located in full sun. Removing foliage will expose the tree’s thin, previously shaded bark to the light, inviting sunscald.
To avoid causing stress or stimulating unsightly growth, never remove more than one-fifth of a Japanese maple’s crown; you should also not prune a branch that is more than half the diameter of the parent stem. In addition, don’t remove more than a quarter of the foliage of any given branch. Each branch is fed by its leaves through photosynthesis. Removing too much of the foliage will starve the tree of nutrients.
If you prune selectively, almost anytime is the right time to prune a Japanese maple.
If you are going to “limb up” your tree by pruning the lowest branches, avoid stress to the plant by removing only a few at a time, not many at once. Never make one cut directly above another or opposite another limb being pruned off in the same year. That might cause decay to coalesce inside the trunk.
The trick to making Japanese maples look great is to separate the branches into overlapping layers that don’t touch each other. Most single-stemmed plants have a series of scaffold branches that radiate in a roughly spiral fashion up the trunk. If a lateral branch from any of these scaffolds grows downward, crossing into the layer below, it should be removed or cut back to a side branch facing up and out. This is how the tree becomes layered, like a series of fans.
While the average tree can handle light pruning, all cuts wound a plant. If your maple is in poor health, make minimal cuts or limit yourself to deadwood removal. To be extra kind, avoid pruning during the tree’s low-energy times: just as leaves emerge in the spring or when leaves are dropping in the fall (just two weeks in each case).
When pruning a Japanese maple, cut up to—but not into—the branch collar. If you cut too far out, you will leave an unsightly stub. If you cut too close to the parent stem (a flush cut), a column of rot will enter the stem. To minimize stress, dieback, and regrowth, do not remove a side branch that exceeds half the diameter of the parent stem.
Bonsaify | When to Pinch Japanese Maples and When to Let ’em Run!
FAQ
When should I prune my Acer palmatum?
When should you prune acers? The golden rule when pruning an acer is to do it only when the tree is dormant. This means pruning between November and March when the tree is not actively growing, and preferably before the end of January.
What is the best month to trim a maple tree?
The best time to prune maple trees is mid-July to August.
How do you encourage new growth on Japanese maples?
Pruning & Trimming Japanese Maples:
You can trim back long shoots a bit to encourage denser growth, but avoid heavy pruning as it can ruin the tree’s natural shape, which is its best feature.
When should I prune my Acer & Japanese maple?
If any pruning is done, then it should be carried out during late, and in any event, before the early spring sap rising. Again, the exception is if there is any damaged wood after a severe winter. Regardless of all the preceding information and advice, someone, somewhere, will want or need to prune their Acer or Japanese maple.
How do you prune Acer palmatum?
Follow these tips for pruning Acer palmatum: 1. Assess and Plan Examine tree structure and identify areas needing pruning. Look for diseased, damaged, and crossing/congested branches. Decide on pruning goals: health, structure improvement, size control. Have a vision for ideal shape and form. Don’t remove too much interior foliage. 2.
When should Acer palmatum be pruned?
Acer palmatum should be pruned in late fall, winter, or early spring while fully dormant. Late November to February is ideal timing in most climates. Here’s why: Pruning during active growth periods of spring and summer risks heavy sap bleeding from cuts. This can lead to fungal infection and weaken the tree.
When should you prune Acer trees?
Pruning Acer trees should be done when the tree is dormant, which is typically around November to January but a few weeks on either side of these months won’t do any harm either. At this time, the tree has no leaves making it easier to access the branches. The idea is to remove any dead or diseased branches while cutting back to the desired shape.
How do you prune Acer trees?
When pruning acers, always try to prune to just above an outward-facing bud. Also, use a clean sharp pair of secateurs or loppers. For larger trees, you may need to use a pruning saw. There are common mistakes that I have learnt to avoid when dealing with Acer trees. Things to keep in mind include:
Should I prune Acer palmatum or Acer platanoides?
Regardless of whether you have a smaller variety like Acer palmatum or Acer platanoides, which is a larger variety; occasional pruning is essential in maintaining the shape and size of many varieties and most respond very well to a good pruning, especially once there established.