Astilbe as Ground Cover: Dense Planting & Coverage Guide
Your astilbe plants reach 18 to 30 inches wide at maturity while your neighbor’s identical variety spreads into dense sweeps covering twice the ground. The difference comes from strategic spacing paired with moisture management. Clumps spread quickly when grown in optimal conditions and require dividing every 3 to 4 years to keep them contained[1]. Here is how to achieve full ground coverage with astilbe.
Understanding Astilbe as Ground Cover
Astilbe has good utility as ground cover in those shaded regions where grass and conventional groundcovers struggle. These herbaceous perennials travel through the underground rhizomes, building increasing clumps that can repress weeds and retain interest all year round[2]. Fern-like foliage becomes bronze or green in early spring, retains an attractive texture throughout the summer and transitions to dried seed heads that persist through winter[2]. The height varies from 8 inches to 4 feet based on the type of landscape the coverage is applied to, enabling coverage solutions for different landscape scales[3].
Partial to full shade with consistent moisture is best for ground cover applications. Full sun locations are effective within northern zones when soil moisture is still present, while southern regions require afternoon-based shading to avoid leaf scorching[2]. Excellent spreading is not easy to achieve and organic matter enriched, well-drained soil provides a base for spreading. Optimal growth can be achieved if soil pH lies in the range of 6.0-neutral[5]. Soil under heavy clay soils should be supplemented with compost to assist drainage and avoid waterlogged soils contributing to root rot.
Best Astilbe Varieties for Ground Cover
Astilbe chinensis varieties have better ground cover performance than other breeds of the genus. These Chinese types of Astilbe spread more through rhizomes, tolerate more sun exposure, and are capable of coping with drought better than Astilbe arendsii hybrids[6].
Top Spreading Varieties
Astilbe chinensis var. pumila is one of the most suitable spreading cultivars to use, with the plants growing 6 inches tall with flower spikes of up to 9 to 12 inches[6]. The dwarf form establishes rapidly and establishes dense mounds of dark green foliage crowned with lilac-pink blooms in early to mid-summer[6].
Another great ground cover is Astilbe simplicifolia Sprite, with small plants that can grow up to anywhere from 10 to 12 inches tall and soft pink flowers that reach up to 18 inches[7]. This species has glossy foliage and relatively slower spreading rate compared with chinensis types[7].
Taller varieties are suitable for use as a ground cover for large spaces. Astilbe chinensis var. taquetii Superba stands 4 to 5 feet high and has purple-rose flowers and readily can span large distances. The sturdy stems hold the plumes upright without staking, while the basal foliage forms multi-layered cover below it.
The secret to effective astilbe ground cover lies in selecting varieties with spreading habits matched to your site conditions.
Calculating Spacing and Plant Quantities
The spacing controls how rapidly astilbe can fill in with uninterrupted coverage. Under ideal conditions this spacing allows plants in space of two or three growing seasons to touch and overlap.
Recommended Spacing by Variety Type
| Variety Type | Recommended Spacing | Coverage per Plant | Plants per 100 sq ft |
|---|---|---|---|
| Dwarf (pumila, Sprite) | 12-18 inches | 1.5-2.25 sq ft | 44-66 plants |
| Standard varieties | 18-24 inches | 2.25-4 sq ft | 25-44 plants |
| Tall varieties (Superba) | 24-30 inches | 4-6.25 sq ft | 16-25 plants |
Dwarf varieties such as pumila require at least 12-18 inches spacing for greater plant cover in order to reach full coverage more quickly. A plant placed 18 inches apart covers about 2.25 square feet at maturity, leaving about 44 plants required for a 100 square feet area. 24 inch space between plants covers 4 square feet per plant so there are about 25 plants needed to fill the same 100 square ft area.
Coverage Calculation Steps
Plant quantities for coverage projects are calculated by dividing by all plant covers at the mature spread size:
- Combine length in feet with width to get square footage
- Take that number and divide it by the square foot covered by one mature plant, per spacing you have chosen
- Round up to get all the area covered
Larger initial spacing promotes coverage but adds to plant expenses. Longer spacing means cost savings in the short term, but time to build with seamless carpet is increased.
Site Conditions and Spacing Adjustments
The spacing decisions aren’t only of the plant size, but also of site conditions. Shadier sites have more rich, moist soil, and consequently faster spreading and should be spaced slightly more widely. Drier areas with more sun exposure like this are better able to use closer spacing to get the right plants established before they’ve been threatened by stress. Slopes require tighter spacing to prevent erosion during establishment and create quicker coverage.
Planting Astilbe for Ground Cover Success
When frost warning wanes or if fall strikes, plant astilbe in spring (early to mid fall[5]). Astilbe cannot stand the drier part of establishment and so summer planting is not advised[1]. Pave holes in twice the area as root balls, incorporating compost to the native soil. Make sure to position the crown about 1 inch below the soil surface, roots spread outward[5]. Backfill with the amended soil and tamp firmly.
Plants should be spaced in staggered rows instead of in straight rows. Place plants in triangular lines and each plant offset from the row above, like this. This configuration eliminates the regimented format of grid patterns and reduces gaps between plants to accelerate coverage.
Watering and Moisture Management
Effective ground cover establishment is driven by a consistent moisture supply. Water extensively once a week throughout the growing season 1 to 2 inches per application during a period of at least one hour of the growing season[1]. Deep watering promotes extensive root development that supports growing. Lower, shallow frequent watering forms poor root systems with weak root systems that develop fragile root systems susceptible to drought stress and fail under severe drought stress under severe water scarcity.
Soil must remain moist but must never become waterlogged. Check that moisture levels check the moisture level with a finger or trowel 2 to 3 inches deep in the ground, or 2-3 inches deep in the ground. Dry soil at this depth shows an area that will need water.
Mulching for Moisture Retention
For spring applications, layer up approximately 2–3 inches of organic mulch around plants. Bark mulch or compost is also used to retain soil water, attenuate temperature extremes, and add organic matter as it decomposes. Mulch should always draw away from a plant crown slightly to avoid rot. The mulch layer should be re-applied annually as it decomposes and integrates into the earth.
Fertilizing and Crown Management
Season early-spring to fertilize astilbe before active growth. If the nutrient is the fertilizer (the nutrient of choice is the nutrient D), a proper fertilizer (10-10-10) applied at the rate as specified on the package can be applied[5]. Phosphorus, which promotes bloom development, and nitrogen, which promotes the growth and spreading of leaves. A second application during autumn after flowering helps early-blooming species plant buds for the next season[2]. Because Chinese astilbe varieties bloom later, they must be fertilised on a fall basis.
Eventually, the crowns of a cultivar of astilbe grow in height, eventually lifting into the air. When rhizomes fully develop, astilbe crowns begin to grow and gradually ascend from the ground as they extend. Push raised crowns back down into the ground gently and put another layer of compost over the area[2]. By doing the above, it prevents crown exposure and desiccation for plants – which will weaken plants to be put under growing speed.
Dividing Astilbe to Expand Coverage
By splitting established clumps, plant vitality remains high while new plants can be sprouted over long distances. Divide astilbe every 3 to 4 years beginning in early spring as new growth can be observed. Dig around the perimeter of the clump and pull up the whole root mass. Cutting through the thick fleshy roots with a sharp spade or knife to form divisions with 3 to 4 eyes. Re-plant divisions right away at the same depth as the original plant. If they become inflamed, water very well and keep the moisture constant until new roots anchor the divisions.
Division is designed to do both during ground cover plantings:
- It avoids overcrowding of flowering in spots as it supports weak growth
- Has free plants to spread cover to other places
Time-wise it would be divided in time divisions should the weather be cool and moisture levels natural.
Drought Tolerance and Recovery
If soil dries out in hot weather, astilbe leaves will curl and brown up. In particular, this temporary setback does not usually make established plants die of such plants. Cut browned foliage to the ground, soak water heavily, and keep moisture stable from then on. If the stress happened during a busy growing season, new foliage typically regrows within weeks. Drought damage from late season does not produce new growth until the next spring.
The Chinese astilbe varieties demonstrate notably better drought tolerance than other species but still perform best with regular moisture. Use them as ground cover when you are unable to irrigate regularly.
Low-Maintenance Ground Cover Benefits
Keep dried flower plumes post-bloom finishes. The seed heads provide winter interest and structure. Many gardeners prefer this naturalistic look over cutting back on wasted blooms. The dried stems must be stripped back in early spring before new vegetation arrives, trimming foliage to ground level if not in style.
Astilbe ground cover requires minimal ongoing maintenance once established. When the dense foliage is in one’s grasp and the weed grows naturally in a stable atmosphere, then that is that–weeding is natural. The problems of pests and diseases that Astilbe has come up are rarely to be found. Even although they thrive in wet conditions, slugs are known to avoid astilbe. Deer and rabbits are not interested in eating the foliage.
Designing with Multiple Varieties
Best ground cover planting will be used with varieties chosen according to the type of flowering period and height. While early season bloomers such as Astilbe Rheinland produce flowers in late spring, late range bloomers like the Astilbe chinensis variety, allow color into late summer; when bloom periods are combined, months of floral interest are added in over the continued coverage of foliage. Mixture heights for up to 24 inches also gives a textural variation and boosts visual interest throughout the planting.
Put astilbe on the ground cover in groups of three to five plants of the same kind for consistent color blocks. Do these groupings over the area where you cover, to create rhythm as you repeat. Mix in various types so that it is not just isolated dots of colour, but an entire color scheme.
Companion Plants for Astilbe Ground Cover
Fellow stalks are closely intertwined in the air-covered by soil covered of asthma grasses and also other shade-tolerant vegetation. Hosta give contrasting leaf shapes and sizes and the conditions under which they grow are similar; however they require very similar situations to be maintained. Ferns provide some lovely textural detail and add subtle frills, and contrast closely to the fluffy astilbe foliage. Brunnera brings spring blue flowers before the astilbe flowers start. These pairings yield layered plantings with increased seasonal significance beyond what astilbe can deliver alone.
Planting on Slopes
Slopes are also particular ground cover challenges that astilbe solves with ease. The spreading root systems stabilize the soil and avoid erosion. Sow astilbe on slopes with closer spacing and in gradual row pattern spacing for slope spacing. Use erosion control cloth during initial installation and after application until plants form. Water must be carefully sloping so as to not lead to runoff before moisture makes its way to the root zone. Drip irrigation or soaker hoses bring moisture right to soil surface without waste.
Hardiness Zones and Regional Considerations
Astilbe forms successfully in zones 4 through 8 and can extend into zone 9. Northern zones can support full sun plantings, provided moisture is sufficient. In the South, astilbe ground cover is restricted to shaded areas, where the dark afternoon sun will not scorch the vegetative leaves. Choose selections based on your specific hardiness zone and site conditions for optimum performance.
Container-Grown vs Bare Root Plants
When establishing ground cover, container-grown astilbe grows more rapidly than bare root plants. The developed root systems transplant, shock free, and start spreading rapidly. Bare root divisions work great for a budget-conscious project because it needs a good enough number of plants to cover. Rehydrate bare roots for 1 to 8 hours prior to planting and keep the hands close while not damaging roots.
Establishment Timeline
The new astilbe ground cover can receive full coverage in 2 to 4 growing seasons, depending on starting space, variety, and site. Fast spreading varieties like Astilbe chinensis pumila are done with thinner spacing, reaching full coverage after 2 seasons given the right moisture and fertility levels. Wider spacing but slow growth will take 4 full seasons for those smaller varieties to close a gap fully. Track and compensate for under-growth with additional plants as necessary during the set-up period.
Site Assessment for Success
The good ground cover is dependent on the extent to which varieties resemble the reality of a site. Calculate daytime sun exposure throughout the year by seasons because deciduous tree canopies give different levels of shade in the spring compared to summer. Dig a 12-inch deep hole to test the drainage of soil and fill it with water, and see how long it drains. Water left after 8 hours is evidence of bad drainage and will need soil amendment before planting. Choose varieties with appropriate heights for the coverage area scale, then try out hardiness zone ratings for your location. Starting with suitable varieties coupled with proper site preparation gives ground coverage that requires little intervention for many years.
Key Sources:
[1] How to Grow Astilbe | American Meadows
[2] Growing Astilbe | Garden Design
[3] How to Plant and Grow Astilbe | Better Homes & Gardens
[5] How to Grow Astilbes | Old Farmer’s Almanac
[6] Astilbe chinensis var. pumila | Missouri Botanical Garden
[7] Astilbe | Chicago Botanic Garden
Lily Morgan is a home gardener. She grows houseplants and designs small-space gardens. She shares what she learns from experience. Lily offers simple, practical tips for plant lovers. Her goal is to help others garden with confidence. She wants to help them grow, one leaf at a time.
