Taxonomy and Botanical Type for Japanese Willows
Plant taxonomy classifies the Japanese willows (or "dappled willows") with which I deal in this article as Salix integra 'Flamingo'. The cultivar name 'Flamingo' refers to the pink color contained in some of the plants' new leaves at the tips of the branches. "Flamingo willow" is another common name for Salix integra 'Flamingo' (I use them interchangeably).
Plant Characteristics, Landscape Uses
Flamingo willows are fast-growing shrubs with potential for good leaf and stem color. Color may be better if shrubs are pruned regularly. These shrubs are foliage plants; they are not grown for their flowers, which are insignificant and appear on catkins (as with pussy willow). The attraction in growing Japanese willows is in their variegated leaves. But this is not just a plant with two-toned leaves; in spring, it is a tri-colored variegated plant, although not as striking as tricolor beech. Older leaves are merely dappled (light green and white), but new leaves may contain a bit of pink. New branches display a red color, especially in spring. They stand about 6 feet tall (4-foot spread) at maturity if left unpruned, but you will almost surely want to prune them to maximize their coloration.
Flamingo Japanese willows are striking enough to stand alone as specimens.
But they can also be grouped together to form hedges.
USDA Plant Hardiness Zones, Sun and Soil Requirements
These shrubs are easy to grow and are not fussy about soil, although they prefer somewhat moist (but not constantly soaked) ground enriched with soil amendments.
Add humus at planting time and supplement periodically thereafter with compost. Plant in a location with full sun. While these bushes can survive in partial shade, it is only in full sun that they will achieve their best color. Apply mulch to retain moisture.
'Flamingo' Not the Only Type of Japanese Willow
If you know someone who grows a Japanese willow, there is a very good chance that it is not the Flamingo type but, rather, Salix integra 'Hakuro Nishiki,' which has been around longer. In fact, Flamingo is a sport (mutation) of Nishiki. Flamingo's color is supposed to be superior to that of Nishiki.
Flamingo Can Be Somewhat High-Maintenance to Grow
I have seen lots of variations in the color of these shrubs, some living up to the colorful name, 'Flamingo', others exhibiting a rather mediocre coloration. As with other plants, such issues may be influenced by many factors, for example, hours of sunlight received, watering, and soil conditions.
Trying to coax superior coloration via pruning (see below) means having to remember to perform the task. In fact, because it's a vigorous grower, Flamingo would not be considered a low-maintenance plant (if you're looking for a compact shrub) even if you didn't care about achieving optimal color: you would still have to prune it just to keep it within bounds.
I am motivated to prune mine because its summertime leaves are not very attractive (green leaves predominate at this time, with variegated leaves taking a back seat).
Care for Japanese Willows
Japanese willow is a shrub that invites pruning, both because it is a vigorous grower (you may wish to keep it more compact) and because it may perform better, color-wise if you prune it regularly.
I mentioned above the height and width this plant can reach at maturity, if left unpruned, at which point the branches will assume more of an arching habit. But it should not be allowed to reach these dimensions. What you would gain in mass and gracefulness, you will lose in color, potentially. To achieve optimal color, fertilize Japanese willows and maintain the following pruning regimen for them:
- Prune heavily in early spring, when still dormant.
- Prune again in late spring to early summer.
- Prune again in August (I end up pruning mine multiple times in late summer).
When I say "prune heavily in early spring," I mean you can trim 1/3 of the older branches right down to the ground, and prune back the top growth (I typically remove a foot or so, but you may wish to take off less or more, depending upon the growth your bush achieved last year) on the remaining branches. New shoots will emerge to take their place. You can even experiment with more drastic pruning because the Salix genus is very tolerant in this regard. My pruning advice pertains to growing Japanese willows as multi-branched shrubs. If you grow the plant as a standard (small tree), you will, of course, be unable to do such drastic pruning, as you will have only one main branch with which to work. But standard-growers will still be able to trim back the upper branches 2 or 3 times per year, to keep encouraging the development of fresh vegetation.
The idea behind all this pruning is to generate new growth. It is the new growth that is most colorful. As a result of that last pruning I mention (for August) above, in my recommended pruning regimen, growers in warmer areas may be able to enjoy red stems on their Japanese willow during the winter -- not unlike what you would expect from redtwig dogwood. Even in cooler areas, winter color might be a bit better on newer wood than on older. But the critical pruning is the one done in early spring -- if you can remember to include it as part of your spring cleaning yard work.