Japanese maples have a reputation for being unapproachable – if you're wielding a pair of secateurs, that is. Elegantly aloof, these beautiful small trees are often allowed to form mounds of foliage at the expense of showing off their gracefully arching branches. And that's a shame, says Sara Katz of Toronto's Wild at Heart Design. "You should be able to see the branching structure," she says, "So many of the unpruned trees I see look like blobs. After pruning, the tree should have a lacy quality and the branches should flow like a stream."
Prune any time after the trees leaf out in the spring, but before the first of August when woody plants like Japanese maples start preparing for winter. "Do a little at a time," Katz advises, "and do a lot of standing back and watching as you prune." Ask yourself if it looks too heavy; the branches should appear to be floating.
The goal, says Katz, is to follow the overall shape of the tree, opening it up a little at a time. Starting at one side, look for branches that flip the wrong way, into the centre of the tree rather than outward. Then, identify the most elegant, arching branches and remove the ones above and underneath them to reveal and show off the best ones. Vary the length of the branches, too, says Katz, to create layers of leafy branches. There should also be a balance of older, thicker branches and younger, willowy stems.
Be sure to cut back any branches that reach the ground, too. "Prune these out, and you get a whole lot of garden back," says Katz. The ground beneath the filtered shade of Japanese maples is a perfect spot to plant 'Jack Frost' Siberian bugloss (Brunnera 'Jack Frost') or one of the many great new cultivars of Japanese forest grass (Hakonechloa macra).
You know it's time to stop, says Katz, when you can see the branching structure. But if you're unsure about pruning your Japanese maple, watch someone do it first, then try cutting just a little at a time until you feel comfortable.