Q: The astilbes in my yard are now blooming. They were planted by the previous homeowner and I really like them. There are pretty white, pink and red flowers, but they don’t seem to last very long. Can you tell me if these plants can somehow be made to bloom for a longer period of time? Thank you.
A: That’s the thing about perennials — each species has its own particular season of bloom, which the gardener awaits with great anticipation. The show begins and then the act is over all too soon, with a year’s long intermission in between acts. And while it works for many flowers, for astilbe, removing the flower heads will not promote continued flowering.
But there is a way to extend blossom time in your astilbe garden. Cultivars of this particular perennial have variations in bloom time, as well as plant height and flower color. That means they range in size from low-growers less than l foot tall to looming 4-foot-tall specimens and bloom from late spring through summer, depending upon the particular cultivar planted. Extending bloom time is simply a matter of popping a few of those plants into your garden to achieve season-long color. Here are just a few of the many astilbe to choose among:
- Early- to-mid-season bloomers (20 to 24 inches tall) include: ‘Deutschland’ (white), ‘Rhineland’ (pink), ‘Bremen’ (deep pink) and ‘Dusseldorf’ (carmine-red).
- Mid-season bloomers (2 to 2-1/2 feet tall) include: ‘Amethyst’ (magenta), ‘Anita Pfeiffer’ (salmon-rose), ‘Erika’ (pink), ‘Etna’ (dark red), ‘Federsee” (carmine), ‘Avalanche’ (white) and ‘White Gloria’ (white, green).
- Late-season bloomers (8 to 12 inches tall) include: ‘Pumila’ (lilac), ‘Sprite’ (pink) and ‘Inshriach Pink’ (pink).
- Late-season bloomers (4 feet tall) include: ‘Taquetti Superba’ (lilac) and ‘Purperkurze’ (reddish-purple).
Astilbe is a delicate, versatile perennial that looks lovely planted in drifts, used as backdrops, and the small astilbes for edgings. They have fern-like foliage and lightly fragrant, feathery flower spikes. The plume-like flower spikes are called panicles, and they bloom in a variety of colors, including red, magenta, pink, salmon, white and cream. They are long-lived perennials and low-maintenance plants when located in lightly shady parts of the garden. Masses of astilbes show very nicely in the garden when planted among daylilies and hostas.
Astilbes prefer a site that receives light to moderate shade and soil with average to slightly below average moisture. The soil should drain well. Astilbes do not like to get water-logged in rain. Provide shade from hot afternoon sun. Astilbes can grow in deep shade but will not flower as prolifically as they do when planted in a space that provides more light.
Astilbes grow quickly and form broad clumps. Their crowns may rise above the soil over time as they mature, so make sure to keep them covered with loamy soil or lift, divide and replant. It is easiest to plant the divisions from other astilbe plants rather than to plant astilbe seed.
Usually, astilbe is divided every three to four years, but I leave mine undisturbed for much longer than that. When it’s time to divide, be prepared. Some astilbe root balls are the weight and consistency of a clump of cement. It takes a very sharp spade or pruning saw to cut through the roots, but it can be done and results in lots of divisions to plant and expand your garden.
Divide in the spring or fall and immediately replant the divisions about 1 to 3 feet apart, depending on the particular growth habit. When planting bare-root plants, make sure the holes are twice as wide as the plants and 4 to 6 inches deep. Place the plants on a mound of soil in the planting hole so the roots are fanned slightly and pointing downward, with the crown planted 1 to 2 inches below the ground level. Backfill with soil and press into place gently, but firmly. Apply balanced organic fertilizer and repeat each spring. Water regularly to keep the soil moist as the plants establish. Water deeply; do not sprinkle.
After blooming has finished for the season, it’s OK to clip off spent flower stems, but I leave them in place for the rest of the growing season in my garden. The flower stems have an unusual ability to look as though they are newly sprouted flower stalks waiting to burst into bloom. I like this effect, so they get to stay. In fall, I cut the plants back hard to pave the way for newly emerging leaves in spring.
For more horticultural information, call The Ohio State University Summit County hotline Tuesdays from 9 a.m. to noon at 330-928-4769, ext. 3.
Dayle Davis is a freelance writer and avid perennial gardener, with a B.A. in communications and coursework in botany, geology and wildflowers. Davis is certified as a Master Gardener under The Ohio State University’s Horticultural Extension. Readers can send in questions regarding lawn and garden issues, which could be featured in a future edition. Questions can be emailed to email@example.com, faxed to 330-665-9595 or sent to Leader Publications, 3075 Smith Road, Suite 204, Akron, OH 44333. Please do not send any leaves, seeds or other organic material.
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