Plant astilbe in spring or fall (RHS, Almanac), when it is warm but not hot. Give it part shade and moist, rich soil that never dries out but is not waterlogged (Iowa State). Set potted plants with the crown just below the soil line, and bare-root crowns 1 to 2 inches deep (Almanac, South Dakota State). Spacing runs 1 to 3 feet depending on the variety (Almanac). Water two or three times a week through the first season (RHS).
Astilbe, sometimes called false spirea, is a shade perennial with ferny leaves and feathery plumes of white, pink, red or purple flowers (Iowa State). Each variety blooms for 2 to 3 weeks, from late May or June for early types to late July or August for late ones, so mixing varieties stretches the show over two or three months (Iowa State). Heights range from 6 to 12 inches for 'Sprite' and 'Perkeo' to about 4 feet for 'Purple Candles' (Iowa State).
When to plant astilbe
| Timing | What the sources say |
|---|---|
| Spring | A preferred window (RHS, Almanac). Iowa State divides clumps in early spring as the foliage emerges, and the Almanac's editors suggest spring for bare-root plants so the roots are not hit by cold |
| Fall | The other good window (RHS, Almanac); NC State also divides in spring or fall. Water well and protect the crown if you plant bare-root in fall (Almanac) |
| Summer | Not ideal: astilbes dislike drying out (Almanac). If you buy a flowering plant in summer, the RHS says plant it straight away and water generously |
| Where it is hardy | NC State lists zones 3a to 9b for hybrid astilbe. In hot climates it needs more shade and steady moisture (Almanac, NC State) |
Our planting calendar shows your frost dates. For spring, plant once the soil has thawed and can be worked, around your last frost; for fall, plant early enough that roots grow before the ground freezes (GardenPal suggestion). The RHS's UK window of late September to mid-October is a guide for mild climates, not a fixed date.
How deep and far apart to plant astilbe
| Astilbe plants | |
|---|---|
| Depth (potted) | Loosen soil 10 to 12 in deep and set the crown just below the soil line (Almanac) |
| Depth (bare root) | Hole 4 to 6 in deep and twice as wide as the roots; crown 1 to 2 in below the soil (Almanac). South Dakota State gives the same 1 to 2 in for bare-root buds |
| Spacing | 1 to 3 ft apart by variety (Almanac). Hybrid astilbe spreads 18 to 24 in (NC State) |
| Light | Part shade, with fewer flowers in full shade; full sun only with abundant moisture (Iowa State). NC State's toolbox lists 2 to 6 hours of direct sun |
| Soil | Fertile, moist and rich in organic matter. Avoid waterlogged or heavy clay soil, or improve it with compost before planting (Iowa State) |
| Bare-root storage | If plants arrive early, keep the packing moist and store them cool, around 40°F (South Dakota State) |
Watering, feeding and dividing
- Water often the first year. Two or three times a week through the first growing season (RHS). After that, water deeply whenever the soil is dry about 1 inch down (RHS).
- Mulch to keep the roots cool and moist; Iowa State suggests adding compost or organic matter around plants every year.
- Feeding: sources differ. The RHS says astilbes in rich, moist soil need no feeding, while the Almanac calls them heavy feeders and suggests a balanced fertilizer in spring and fall. Annual compost is a middle path (GardenPal note).
- Divide clumps every 3 to 4 years (Almanac), every 4 years (RHS, NC State) or every 4 to 6 years (Iowa State), in early spring as the foliage emerges.
- Crowns rise above the soil over time; top them up with soil or compost (Almanac).
Astilbe in containers
Only dwarf astilbes, 1 to 3 feet tall, suit containers, and potted plants need watering all through the growing season (RHS). The Almanac suggests pots at least 16 inches wide, and in cold areas, burying the pot in the garden or wrapping it for winter. Use a mix that holds moisture but still drains (GardenPal suggestion).
Fall and winter
- Leave the plumes. Faded plumes turn brown and look good through winter (Iowa State). The RHS cuts stems and old leaves to the ground in December or January, before new shoots appear.
- Mulch lightly in fall (Almanac). Astilbe is hardy to about zone 3 (NC State, Almanac).
- Self-sown seedlings may appear if plumes are left; they take about three years to flower and may not match the parent (RHS).
Pests and problems
NC State reports no serious pests, with occasional whitefly, Japanese beetle and black vine weevil. Vine weevil adults leave notches along leaf edges (RHS). Possible diseases include powdery mildew, wilt and leaf spots (NC State); good spacing and watering at the soil line help (Almanac). Scorched or browning leaves usually mean too much sun or dry soil (RHS, Almanac). Deer and rabbits tend to avoid astilbe (NC State).
Astilbe near the vegetable garden
Astilbe is a shade plant, so it fits the shady edge of a yard rather than a sunny vegetable bed (GardenPal note). Iowa State pairs its fine leaves with bold hostas, and NC State says the flowers attract butterflies. The RHS suggests other moisture lovers such as primulas. For more shade color, see when to plant hellebores, when to plant tuberous begonias and when to plant caladiums.
Frequently asked questions
When is the best time to plant astilbe?
Spring or fall, when it is warm but not hot (RHS, Almanac).
How deep do you plant bare-root astilbe?
With the crown 1 to 2 inches below the soil (Almanac, South Dakota State Extension).
How far apart should astilbe be planted?
About 1 to 3 feet apart depending on the variety (Almanac).
Can astilbe grow in full sun?
Only with abundant moisture; part shade is best (Iowa State).
How often should I water new astilbe?
Two or three times a week through the first growing season (RHS).
How often should astilbe be divided?
Every 3 to 6 years depending on the source, in early spring (Almanac, RHS, Iowa State).
Enter your frost dates to time a spring or fall astilbe planting.
Open itSources
- Virginia Cooperative Extension, "Companion Planting in Gardening" (SPES-620P)
- University of Maryland Extension, "Vegetable Succession and Companion Planting"
- Oregon State University Extension, "Companion Planting"
- Penn State Extension, "Herbs Make Good Plant Partners and Companions"
- University of Minnesota Extension, "Planting the vegetable garden"
- USDA Plant Hardiness Zone Map
- NOAA NCEI U.S. Climate Normals (frost/freeze data)
- Iowa State University Extension, "Astilbe site requirements"
- Iowa State University Extension, "Growing astilbe in Iowa"
- NC State Extension Gardener Plant Toolbox, "Astilbe x arendsii"
- Royal Horticultural Society, "How to grow astilbes"
- The Old Farmer's Almanac, "Astilbe"
- South Dakota State University Extension, "How to plant bare-root perennials"
Pairings are summarized in our own words from extension-service guidance. Research support for many companion effects is limited, so treat them as good habits, not guarantees.