Ornamental · Saxifragaceae
Astilbe
Astilbe × arendsii
Give it shade and soil that stays damp, and astilbe will fill your dark corners with feathery plumes.
Partial shade
Every 2–4 days
USDA 3–9
1–4 ft · 0.3–1.2 m
Overview
If you have a damp, shady corner where nothing seems happy, astilbe is your answer. Its feathery flower plumes lift above soft, ferny foliage in early to midsummer, in colors that run from white through pink to deep crimson. The hybrid you will find in most gardens, Astilbe x arendsii, is a tough perennial that returns faithfully each year across zones 3 through 9.
Here is the lovely part: unlike most shade plants, astilbe truly blooms, and blooms generously, away from direct sun. Those branching, downy plumes are why it picked up the old nicknames false spirea and false goat's beard. When the flowers fade, the cut-leaf foliage carries on looking good all season and knits together into a soft groundcover beneath trees or along a shady wall.
There is really only one thing it cannot abide, and that is dry soil. Keep the ground rich and steadily moist and astilbe is just about effortless, brushing off deer and asking only for a division every few years. Let the roots go thirsty in hot sun and the leaf edges brown and it pouts, but a good soaking is usually all it takes to set things right again.
Care
The short version: part to full shade, soil that stays 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, which makes it one of the rare perennials that flowers well without much sun at all. It can take a bit more sun in cooler areas, but only where the soil never dries out, and a stretch of deep afternoon shade suits it perfectly in hot-summer gardens.
Water
This is the one thing astilbe really insists on, so do not stress about the rest. Keep the soil evenly damp, watering every 2 to 4 days and soaking it more deeply when summer turns hot. If the ground dries out the leaf edges brown and the plant fades, sometimes slipping into an early rest, but a good watering usually coaxes it back.
Soil
Set it into rich, humusy loam that stays moist yet still lets water drain away, and mix in plenty of compost. Astilbe is relaxed about pH, growing well anywhere between 5.5 to 7.5, so put your attention on the soil texture and the moisture rather than fussing over the number.
Humidity
Everyday garden humidity is just right, and there is no target you need to hit. Damp leaves crowded together in stale air can invite powdery mildew, though, so leave clumps room to breathe and the problem mostly looks after itself.
Feeding
A balanced all-purpose fertilizer through the growing season keeps fresh plumes coming along. A compost mulch in summer earns its keep twice over, feeding the plant gently while holding onto the moisture astilbe leans on.
Pruning
Snip off the faded plumes for a neat look, or leave them in place for winter interest, since the dried heads catch the frost beautifully. Trim the foliage back in late fall or early spring, just before the new shoots start to rise.
Size & spacing
Depending on the cultivar, plants reach 1 to 4 feet (30 to 120 cm) tall, from tidy little edgers to taller back-of-the-border types. Each clump widens to 12 to 24 inches (30 to 60 cm), so give them that much room and they will knit together without crowding each other out.
When to plant
Because astilbe is grown from divisions and not from seed, its calendar is about planting and blooming rather than sowing. Tuck divisions into the ground in spring or early fall, and the plumes will unfurl from late spring through summer, with plenty of cultivars hitting their stride 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
Almost all astilbe woes turn up in the leaves, and dry soil causes more of them than any bug or fungus ever will. Find the symptom you are seeing below, match it to the cause, and step in early before scorching or disease spreads through the whole clump.
Crispy brown leaf edges and a plant that quits early
Take heart, because this is just drought stress, and it is one of the easiest things to put right. The roots got too dry, often because the spot sits in too much sun or a heat wave rolled through, and the plant drops its scorched leaves and naps early to keep itself safe. Give it a long, deep drink so the soil stays evenly damp, tuck a compost mulch around the base, and shift it somewhere shadier if the ground keeps baking. It will come back for you.
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 dusty white film spreading over the leaves
What you are seeing is powdery mildew, a fungus that moves in when the air sits still and damp around plants packed too close together. The good news is that it almost never kills astilbe, it mostly just dulls the look of the leaves. Let some air move through by spacing things out and splitting tight clumps, snip off the worst leaves, and try to keep water off the foliage when you water.
Fix:
- Improve air circulation by spacing and dividing crowded clumps
- Remove affected foliage
- Avoid overhead watering
Leaves chewed to lace in the middle of summer
The likely visitors are Japanese beetles, which munch the soft green tissue and leave only the veins behind, giving the leaves that lacy look. You can usually catch the shiny metallic beetles sitting right on the plant. Head out in the cool of the morning while they are still sluggish and tip them into a bucket of soapy water, and only turn to an approved insecticide if they show up in large numbers.
Fix:
- Hand-pick beetles into soapy water
- Treat with approved insecticide if infestation is heavy
Toxicity
You can plant astilbe with a clear conscience around animals and children. The ASPCA does not list it as toxic, and trusted sources record no poisoning in pets, so go ahead and use it along paths and near play areas without a second thought.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax if a curious cat takes a bite, because astilbe does not appear on the ASPCA toxic list. About the worst that might happen is a little drool after a mouthful of the stringy foliage.
Dogs None
A dog can lean into it or chew on a plume with no harm done. Eating a big helping of any plant can upset a dog's tummy for a day, but there is no toxin in the astilbe itself to worry about.
Horses Safe
Nothing in astilbe is recorded as harmful to horses, and the plant is far too little to ever make up much of their grazing in the first place.
Rabbits Safe
Rabbits are welcome to nibble it safely. In practice the tough, ferny leaves are something they usually walk past, choosing softer greens instead.
Livestock Safe
Cattle, goats, and sheep have nothing to fear from astilbe, since it carries none of the toxins that make a few garden plants a problem near pasture.
Birds Safe
Birds are perfectly safe around it, whether they tuck into the foliage for cover or peck at the plant.
People Safe
It is gentle to handle and fine to grow with little ones nearby, though do remember it is an ornamental for the garden, not something for the dinner table.
Varieties
There are dozens of named astilbe cultivars, and they vary mostly in the color of their plumes and how tall they grow. The three below are the ones you will meet most often, and together they show off the range.
Fanal
A neat, compact choice that may hold the deepest crimson-red plumes you will find on any astilbe, lifted above leaves that start out bronze and settle into a dark green tinged with red.
Bridal Veil (Brautschleier)
Soft, arching white plumes give it a light, bridal feel, and that is exactly how it came by its name.
Amethyst
A taller grower topped with lilac-purple plumes that tend to open on the early side of the season.
How to propagate
Astilbe is multiplied by division, which happens to be the very same task that keeps an older clump healthy and full. It is simple, and it will not cost you a penny.
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.
Almost every astilbe is started by division rather than from seed, and it is a friendly job. When spring is just waking up or fall is settling in, dig up a crowded clump, gently pull or cut the rootball into pieces, and tuck them back into rich, damp soil at the same depth they were sitting. Repeat this every 3 to 4 years. Each new piece takes one season to find its feet, and the blooms usually return the year after.
Myths
Astilbe must have deep shade and will refuse to bloom with any sun on it.
It does favor part shade, yet where summers stay cool it will happily grow and flower in full sun. What it truly asks for is steady moisture, not gloom, so keep the soil damp and the sun stops being much of a worry at all.
Astilbe will poison your pets.
There is nothing to back this up. Astilbe is not on the ASPCA toxic plant list, and trusted sources note no toxicity in cats or dogs, which makes it a comfortable pick for a garden you share with animals.