Ornamental · Saxifragaceae
Astilbe
Astilbe × arendsii
Hand it shade and soil that stays damp, and astilbe answers with soft, feathery plumes lifting out of ferny foliage.
Partial shade
Every 2–4 days
USDA 3–9
1–4 ft · 0.3–1.2 m
Overview
Astilbe is the plant for that damp, shaded corner where almost nothing else will settle in. Soft, feathery flower plumes push up above ferny, finely cut green leaves in early to midsummer, ranging from white through pink to a deep crimson. The hybrid most gardens grow, Astilbe x arendsii, is a tough perennial that returns season after season across zones 3 through 9.
What marks astilbe out among shade plants is that it truly flowers, and flowers heavily, away from direct sun. Those soft, branching plumes are the reason for its old names, false spirea and false goat's beard. Below the bloom the cut-leaf foliage holds its looks all season and knits together as a groundcover under trees and along a shaded north wall.
Dry soil is the one thing it will not put up with. Keep the ground rich and steadily moist and astilbe is nearly self-sufficient, brushing off deer and asking only for a division every few years. Let it cook in the sun with parched roots and the leaf edges scorch brown and the whole clump sulks.
Care
The short version: part to full shade, soil kept evenly damp and full of organic matter, and a compost mulch over summer to lock the moisture in.
Light
Astilbe is happiest in part to full shade, one of the few perennials that flowers dependably out of the sun. It will accept more sun in cooler regions, but only where the soil never dries, and deep afternoon shade serves it well in hot-summer areas.
Water
Here is the plant's single real demand. Hold the soil evenly moist, watering every 2 to 4 days and reaching deeper through summer heat. Let the ground go dry and the leaf edges brown and the foliage falters, sometimes driving the plant into early dormancy.
Soil
Plant it in rich, humusy loam that grips moisture yet still drains, with plenty of compost dug through. Astilbe is relaxed about pH, doing fine anywhere from 5.5 to 7.5, so the texture and the dampness count for far more than the number.
Humidity
Plain garden air suits it and there is no target to chase. Packed, damp foliage in dead air does coax out powdery mildew, so leave clumps room to breathe and that problem looks after itself.
Feeding
A balanced all-purpose fertilizer across the growing season keeps the plumes coming. A summer compost mulch pulls double duty, feeding slowly while holding the moisture astilbe leans on.
Pruning
Snip off the spent plumes for a neat finish, or let them stand for winter interest, since the dried heads hold frost well. Cut the foliage down in late fall or early spring before the new shoots push up.
Size & spacing
Plants stretch from 1 to 4 feet (30 to 120 cm) tall depending on cultivar, from low edgers to back-of-border kinds. Each clump reaches 12 to 24 inches (30 to 60 cm) across, so set them at that spacing to fill in without crowding.
When to plant
Astilbe grows from divisions rather than seed, so its year turns on planting and bloom instead of sowing. Set the divisions out in spring or early fall, and the plumes unfurl from late spring through summer, with many cultivars at their fullest 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
Nearly all astilbe trouble surfaces in the leaves, and dry soil drives more of it than any insect or fungus. Match the look of the damage below to its cause, then step in before scorched foliage or mildew spreads through the clump.
Crisped brown leaf margins and a plant shutting down early
What you are looking at is drought stress. With astilbe the trail leads straight to soil that went dry, usually under too much sun or during a heat spell. The leaves crisp at their edges, the plant drops the scorched foliage, and it can slip into dormancy ahead of schedule to spare itself. Soak the ground deeply so it stays evenly damp, spread a compost mulch, and shift the clump into deeper shade if the spot runs hot.
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 chalky white dusting settling over the leaf surfaces
That pale film is powdery mildew, a fungus that moves in when the air sits humid and still around plants packed too closely. It seldom finishes off an astilbe, but it dulls and mars the cut-leaf foliage. Open the planting so air moves through, split tight clumps apart, strip off the worst-coated leaves, and keep the water off the foliage when you irrigate.
Fix:
- Improve air circulation by spacing and dividing crowded clumps
- Remove affected foliage
- Avoid overhead watering
Foliage reduced to lacy skeletons at the height of summer
Japanese beetles are almost always the cause. They strip the soft green tissue from between the leaf veins, so what remains is a thin lacework of ribs. You can usually catch the metallic-shelled beetles working right on the foliage. Flick them into a bucket of soapy water early in the day while they are sluggish, and bring out an approved insecticide only when the chewing turns heavy.
Fix:
- Hand-pick beetles into soapy water
- Treat with approved insecticide if infestation is heavy
Toxicity
Astilbe is a safe plant to keep around animals and children. The ASPCA does not list it as toxic, and approved sources record no poisoning in pets, so you can set it along paths and play areas without concern.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Astilbe is absent from the ASPCA toxic list, so a cat that takes a bite of leaf has nothing to fear. At worst, a mouthful of the fibrous foliage might bring on a bit of drool.
Dogs None
A dog can rub past the clump or chomp a plume with no harm done. A large helping of any plant may loosen the stomach for a day, but the astilbe itself holds no toxin.
Horses Safe
Nothing toxic is recorded for horses, and the plant stands far too low to make up any real share of what they graze.
Rabbits Safe
Rabbits can nibble the foliage safely. The tough, ferny leaves usually leave astilbe among the plants they skip in favor of softer greens.
Livestock Safe
Cattle, goats, and sheep run no risk from astilbe, which carries none of the toxins that turn certain garden plants into a pasture worry.
Birds Safe
The plant is no danger to birds, whether they tuck into the foliage or pick at the plumes.
People Safe
Astilbe is safe to handle and to grow around children, though it is an ornamental and not something for the kitchen.
Varieties
Astilbe runs to dozens of named cultivars that part ways mostly in plume color and height. These three appear most often and map out the range.
Fanal
A compact selection bearing what may be the deepest crimson-red plumes in the genus, lifted above leaves that break out bronze and settle into a dark green washed with red.
Bridal Veil (Brautschleier)
Its white plumes arch over in loose, gauzy sprays, the bridal look that gave it the name.
Amethyst
A taller form whose lilac-purple plumes open comparatively early in the season.
How to propagate
Astilbe is increased by division, the same job that keeps an aging clump going strong. 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 raised almost entirely by division rather than from seed. In early spring or fall, lift a crowded clump, cut or pull the rootball into pieces, and set each one back into rich, moist soil at the depth it grew before. Repeat every 3 to 4 years; each piece needs a full season to root in and usually sends up plumes again the year after.
Myths
Astilbe will only grow in deep shade and refuses to flower with any sun on it.
It does favor part shade, yet in cooler climates it grows and blooms in full sun without trouble. The true demand is steady moisture, not gloom, so keep the soil damp and the sun stops being much of an issue.
Astilbe will poison your pets.
Nothing supports this. Astilbe is not on the ASPCA toxic plant list, and approved sources note no toxicity to cats or dogs, making it a sound pick for a garden shared with animals.