Ornamental · Saxifragaceae
Astilbe
Astilbe × arendsii
Give it shade and soil that never dries out, and astilbe lights up the dark corners with feathery plumes.
Partial shade
Every 2–4 days
USDA 3–9
1–4 ft · 0.3–1.2 m
Overview
Astilbe is the plant for the damp, shady spot where little else wants to grow. Its feathery flower plumes rise above ferny green foliage in early to midsummer, in shades from white to pink to deep crimson. The hybrid grown in most gardens, Astilbe x arendsii, is a hardy perennial that comes back year after year in zones 3 through 9.
What sets astilbe apart from most shade plants is that it actually flowers, and flowers well, out of direct sun. It earns its old names of false spirea and false goat's beard from those soft, branching plumes. Above the bloom, the cut-leaf foliage stays handsome all season and fills in nicely as a groundcover under trees and along the north side of a house.
The one thing it will not forgive is dry soil. Keep the ground rich and consistently moist and astilbe is close to carefree, shrugging off deer and asking only that you divide it every few years. Let it bake in the sun with dry roots and the leaves brown at the edges and the plant sulks.
Care
The short version: part to full shade, soil that stays evenly moist and rich in organic matter, and a compost mulch through summer to hold the water in.
Light
Astilbe does best in part to full shade, which makes it one of the few perennials that flowers reliably out of the sun. It will take more sun in cooler regions, but only if the soil never dries out, and deep afternoon shade suits it well where summers are hot.
Water
This is the plant's one real demand. Keep the soil consistently moist, watering every 2 to 4 days and going deeper through summer heat. Let the ground dry out and the foliage browns at the edges and declines, sometimes forcing the plant into early dormancy.
Soil
Plant in rich, humusy loam that holds moisture but still drains, with plenty of compost worked in. Astilbe is easygoing about pH, growing well anywhere from 5.5 to 7.5, so the texture and the moisture matter far more than the number.
Humidity
Ordinary garden humidity is fine and there is no figure to aim for. Crowded, damp foliage in still air does invite powdery mildew, so give clumps room to breathe and that takes care of itself.
Feeding
A balanced all-purpose fertilizer through the growing season keeps the plumes coming. A summer compost mulch does double duty, feeding the plant slowly while holding the moisture astilbe depends on.
Pruning
Deadhead the spent plumes for a tidy look, or leave them standing for winter interest, since the dried heads catch frost nicely. Cut the foliage back in late fall or early spring before the new growth pushes up.
Size & spacing
Plants range from 1 to 4 feet (30 to 120 cm) tall by cultivar, from low edgers to back-of-border types. Each clump spreads 12 to 24 inches (30 to 60 cm), so space them to that width to fill in without crowding.
When to plant
Astilbe is grown from divisions, not seed, so its calendar runs on planting and bloom rather than sowing. Set divisions out in spring or early fall, and the plumes open from late spring through summer, with many cultivars peaking in June and July.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Seed is difficult and slow; most gardeners start from divisions rather than seed.
- Plant: Plant divisions in spring or early fall.
- Harvest: Late spring through summer (varies by cultivar; many bloom June-July).
Hardiness
USDA hardiness zones: 3–9
Temperature: down to -40°C
Troubleshooting
Most astilbe trouble shows up in the leaves, and dry soil is behind more of it than any pest or disease. Match what you see below to the cause, then act before scorched foliage or a fungus takes hold across the clump.
Browned, scorched leaf edges and early dormancy
This is drought stress, and with astilbe it traces straight back to soil that dried out, usually in too much sun or a summer heat spell. The plant may shed its scorched leaves and go dormant early to protect itself. Water deeply to keep the soil evenly moist, lay down a compost mulch, and move it into more shade if the spot bakes.
Fix:
- Water deeply and consistently to keep soil evenly moist
- Apply a compost or organic mulch to retain soil moisture
- Move or site plants in part to full shade
A white powdery film across the leaves
This is powdery mildew, a fungus that settles in when the air is humid and stagnant around crowded plants. It rarely kills astilbe but it spoils the look of the foliage. Open the planting up for better airflow, divide tight clumps, pull the worst leaves, and keep water off the foliage.
Fix:
- Improve air circulation by spacing and dividing crowded clumps
- Remove affected foliage
- Avoid overhead watering
Lacy, chewed-up leaves in midsummer
Japanese beetles are the usual culprit, eating the soft tissue between the veins and leaving a skeleton of lace behind. You will often spot the metallic beetles right on the plant. Knock them into a tub of soapy water in the morning when they are slow, and reach for an approved insecticide only if the feeding gets heavy.
Fix:
- Hand-pick beetles into soapy water
- Treat with approved insecticide if infestation is heavy
Toxicity
Astilbe is a safe plant to grow around animals and children. It is not listed as toxic by the ASPCA, and approved sources record no poisoning in pets, so you can plant it freely along paths and play areas without worry.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Astilbe is not on the ASPCA toxic list, so a cat that nibbles a leaf has nothing to fear. The worst you might see is a little drool if it eats a lot of the fibrous foliage.
Dogs None
Dogs can brush against it or chew a plume without harm. A big mouthful of any plant can loosen a dog's stomach for a day, but the astilbe itself carries no toxin.
Horses Safe
No toxicity is recorded for horses, and the plant is far too small to be a real part of their grazing anyway.
Rabbits Safe
Rabbits can graze the foliage safely. The tough, ferny leaves tend to make astilbe one of the plants they pass over in favor of softer greens.
Livestock Safe
Cattle, goats, and sheep face no risk from astilbe, which holds none of the toxins that make some garden plants a worry in pasture.
Birds Safe
The plant poses no threat to birds, whether they shelter in the foliage or pick at it.
People Safe
Astilbe is harmless to handle and grow around children, though it is an ornamental rather than something meant for the kitchen.
Varieties
Astilbe comes in dozens of named cultivars that differ mostly in plume color and height. These three turn up most often and show the range.
Fanal
A compact cultivar carrying perhaps the darkest crimson-red plumes of any astilbe, set off by foliage that emerges bronze and matures to a dark green flushed with red.
Bridal Veil (Brautschleier)
Its arching white plumes have an airy, bridal look that earns the name.
Amethyst
A taller type with lilac-purple plumes that open relatively early in the season.
How to propagate
Astilbe is multiplied by division, which doubles as the routine that keeps an aging clump vigorous. It is easy, and it costs you nothing.
DivisionEasy
Early spring or fall, dividing clumps every 3 to 4 years when overcrowded. · One growing season to re-establish, often flowering the following year.
Astilbe is grown almost entirely from division rather than seed. In early spring or fall, lift a crowded clump, split the rootball, and replant the pieces in rich, moist soil at the depth they sat before. Do this every 3 to 4 years, and each division takes a full season to settle in, usually blooming again the year after.
Myths
Astilbe needs deep shade and will not bloom in any sun.
It does lean toward part shade, but in cooler regions it will grow and flower in full sun without complaint. The real requirement is steady moisture, not darkness, so keep the soil damp and the sun becomes far less of a problem.
Astilbe is poisonous to pets.
There is no evidence behind this. Astilbe is not on the ASPCA toxic plant list, and approved sources record no toxicity to cats or dogs, so it is a safe choice for a garden shared with animals.