The dappled willow is very popular, but when and how do you prune it? Source: springmeadownursery.com
Question: I planted a dappled willow in my garden this summer. Should I prune it in the fall? And does it need any kind of winter protection?
Lili
Answer: First, the dappled willow (Salix integra ‘Hakuro-nishiki’*) is a shrub that is also known as variegated willow, flamingo willow or dappled Japanese willow. It’s grown for its narrow leaves mottled white and pink in the spring. As the spring progresses, the pink fades away, leaving a white and green color, then the white disappears too, giving entirely green leaves by the end of the summer. There is no noticeable fall leaf coloration, but younger branches take on a reddish tinge that offers some winter appeal.
*S. integra ‘Flamingo’ is also widely sold and is claimed to be an improved version of ‘Hakuro-nishiki’ with a better pink coloration in the spring. I must admit I can’t see any difference and the Royal Horicultural Society seems to agree with me, as they list S. integra ‘Nishiki Flamingo’ as a synonym.
To Prune or Not to Prune?
“Should I prune it in the fall?”
In my opinion, you didn’t ask the right question. The question should be “do I have to prune it… ever?”, because one of the laidback gardener’s main principles is that you never prune plants just because they’re there. You have to have a good reason to do so.
And gardeners usually have two reasons for wanting to prune their dappled willow.
First, it is commonly pruned to keep it dense and compact. Indeed, the dappled willow is actually a large shrub with a somewhat arching branches that can grow to about 12 feet (3.5 m) in height and 8 feet (2.5 m) or more in diameter if it’s never pruned. Personally, I like it that way and never prune mine. My specimen is now about 8 feet (2.5 m) in height and 5 feet (1.5 m) in diameter after 18 years, which I consider quite acceptable. Of course, I planted it taking into account its future size, in the company of other large shrubs in a spot where access for pruning would be difficult anyway. I like that fact that it requires no pruning whatsoever under my conditions.
Late Winter/Early Spring Pruning
But I’m an exception to the rule. Most people prune their dappled willow severely each year, down to about at 6 to 12 inches (15 to 30 cm) from the ground. This results in a modestly sized, rather rounded shrub about 5 feet (1.5 m) in height and diameter.
And fall is not the usual pruning season. Rather, it is generally pruned in late winter or early spring, at snow melt or, in warmer regions where there is no snow, around the same time as the shrub blooms, which it does quite discretely, with rather small catkins.
As a laidback gardener, I find forcing plants to take on an unnatural shape time-consuming and unnatural. If I want a shrub 5 feet (1.5 m) tall and wide, I’ll put in a modestly sized shrub that naturally matures at 5 feet (1.5 m) in height and diameter and stays there (there are so many of them!), not a big shrub I’ll need to cut back every year.
A Mid-Summer Trim
That’s pruning number 1, but a lot of gardeners, much harder working than myself, give the shrub a second trim in mid-summer (July or early August) too, when its foliage has lost much of its variegation. This is just a quick trim, shortening all the branches by about 6 inches (15 cm). This quickly stimulates dense regrowth just as variegated pink and white as it was in the spring, although the color is not as long lasting. (The pink, especially, fades quickly under the effect of the summer heat.) Trimming a dappled willow in this way gives you something that looks like a shrub with a poodle cut. Not exactly what I want in my haphazard garden, with its “back to nature” theme!
Lollipop Willows
The dappled willow is often sold grafted onto a straight trunk (this is called top-grafted or standard form) in order to form a small tree, looking rather like a lollipop at the time of purchase. Does this change anything in how you prune it?
Not really: it’s the same shrub, except now lifted off the ground as if on stilts, and will need essentially the same care. So prune it once a year, twice a year or not at all: it’s your choice.
Basic Dappled Willow Care
The dappled willow is a pretty easy plant to grow, doing fine in most garden conditions.
It prefers full sun or, in a pinch, partial shade, in soil of just about any quality, well-drained, but still, always a bit moist. You may need to water several times the first year until it settles in. Like most shrubs, it will prefer a good mulch to keep its root zone cool and moist. Note too that, unlike large willows (some are huge trees!), its root system is not invasive.
Although some sources claim the dappled willow is to hardy to only zone 5, the species (S. integra) is native to cold northern regions of Eastern Asia, from Japan to northern China and even Siberia and is perfectly hardy in zone 3b. The cultivar seems just as hardy as the species.
Beware of fertilizers rich in nitrogen with this plant: they stimulate meteoric growth … but the beautiful pink and white colors are lost. Use instead a slow-release organic fertilizer where the first of the three numbers (nitrogen) is less than 8. Moreover, it’s not a needy shrub and won’t require a lot of fertilizer: a single fertilizer application of slow release every three or four years will probably be plenty.
Finally, when buy a standard (tree-form) dappled willow (i.e. a lollipop), remember that it’s actually two plants in one: a dappled willow grafted on top of a trunk-forming willow* with green leaves. Any branches that appear from the base of the plant or from below the graft point will be from from the rootstock, not dappled willow, and will not bear variegated leaves, but entirely green ones. You’ll have to prune off these reversions to maintain both the lollipop look and the variegated coloration.
*Although S. integra itself is very hardy, top-grafted forms (lollipops) are often grafted onto a less hardy rootstock. If you live in a cold climate, make sure the rootstock is at least as hardy as the top-graft!!
The dappled willow: striking whether you prune it or not… and may I suggest the latter!