Why America Loves Astilbes

American gardeners are in the midst of a passionate love affair with Astilbes. Native to the far east, these beautiful plants and their hybrids have revolutionized the perennial possibilites of moist, shaded American gardens. Astilbes are companions of ferns and impatiens--they're some of the few flowers that make big color in full or partial shade.

The vast majority of the scores of hybrids now available are the work of one man, master hybridizer Georg Arends (Yes, that's why you keep seeing "arendsii" tacked onto hybrid names.) Mr. Arends, working in Ronsdorf, Germany spent decades hybridizing sedums, phlox, campanulas... and his first love, astilbes.

From tiny dwarfs to big draping hybrids, astilbes are all quite easy to grow, as long as their ground is not in the blazing sun and does not dry out for long. They must have plenty of moisture, so choose your locations carefully. If the soil is not loamy, add some peat moss or other moisture-retaining material. You'll know after one growing season whether your plants are happy where you've put them. If not, think about moving them to a better spot before they weaken.

With these plants, mulching is important, especially if they are planted where they will get some direct sun. Bark chips or any other good moisture-retaining top mulch will be very helpful in maintaining the constantly-moist ground they prefer.

They need no more than the usual feeding, like most flowering perennials. For feeding perennial gardens, my favorite perennial expert, Frederick McGourty, recommends familiarizing yourself with standard perennial flower fertilizers, which are always labeled with three numbers in a sequence, such as 5-10-5 or 5-10-10, or 10-10-10. These numbers on the bag refer to percentages of Nitrogen, Phosphorus and Potassium, in that order. McGourty explains that the most important element here for flowering plants is the middle number, Phosphorus, so he recommends choosing a fertilizer with the middle number no lower than the other two.

If your garden is new, try to rake in your fertilizer a week or two before planting. And in later years, one feeding in spring (remove the mulch, and rake it in) should do. If you use dry granular fertilizer, remember to scatter it when the soil is wet and the foliage of your plants is dry. Dry fertilizer sticking to stems and leaves can burn the plants.

If you're new to the neighborhood, it's always good to give your local county extension agent a call, and discuss soils and feeding with him or her. That's what they're there for. It's great local advice, and it's free. You'll find the number in the phone book under US Government, Cooperative Extension Services.

In the right locations, astilbes grow vigorously. In fact, after a year or two, you'll have big clumps you'll want to divide. And that's easy too. The best time is just after flowering. Water deeply, and then just dig up the clumps and pull the roots into pieces. Try to keep the pieces large, so each one will quickly become a full size plant. Of course, get them back into the ground as soon as possible.

One of the beauties of this perennial group is that you can use them in either informal ways for casual fountains of color as you see in the big photo at the top of this page, or you can also use them in a more formal way. I once divided about 5 big clumps into about 30 plants, and planted 15 on each side of a short pathway. The next spring, the path was elegantly lined with perfectly matching plants, all with identical plumes in height and color. After bloom, the walk was edged with neat handsome hedges of their foliage. Garden designers also know that many astilbes put on a second show with changes in fall foliage color, too.

Great companion plants include Japanese and Siberian iris, trilliums, ferns, hostas, cimicifuga, ligularia and of course, annual impatiens.

Fortunately, most all astilbes are dependably winter hardy. I've grown them in Zone 3, and never lost one. Normally, they need no special protection.