Perennial Overview: Astilbe

astilbe

Discover how to grow Astilbe with instructions on starting seed, transplanting, site selection, care and maintenance, water and fertilization requirements, pests and disease, and harvesting and storage.

Astilbe Stats at a Glance

Botanical Name: Astilbe x arendsii

Common Name(s): False spirea

Height: 18”-4 feet

Soil Conditions:  Well-drained, moist, fertile

Sun: Partial shade

Soil pH Conditions: Slightly acidic

Planting Instructions

Can I Start Astilbe from Seed?

Astilbe is notoriously difficult to grow from seed.  Many seed catalogs and garden centers sell astilbe plants.

The best method of propagation is through division or cutting.

To start indoors, fill individual peat pots with a fertile commercial soil starter and moisten.  Sprinkle the seeds on the surface of the soil. Press them lightly into the soil to ensure contact with growing medium. Place in a room with a constant temperature of 65-70°F.  Cover with clear plastic wrap to maintain the soil moisture and temperature.  Keep the soil moist.  When seedlings appear, remove the plastic wrap and move to a sunny location.

 

When to Start Seeds: >6-8 weeks prior to planting
Time to Germination: 4-5 weeks
Light/Darkness Requirements: Dark

 

When Do I Plant Astilbe?

Astilbe are cold sensitive and should not be planted until after the last frost and the soil has warmed.

You can hasten the warming of the soil with black plastic mulch.

 

Where Do I Plant Astilbe?

Astilbe plants prefer shady, moist locations with high fertility but can be planted in sunny locations as long as they are kept moist.

Astilbe plants perform best in loamy, well-drained soil, high in organic matter that is slightly acidic. Does not tolerate heavy clay soils.  Incorporating several inches of organic matter into the soil when preparing the bed will improve growth and development.

Soil Conditions:  Well-drained, moist, fertile
Sun: Partial shade
Soil pH Conditions: Slightly acidic

 

How Far Apart Do I Plant Astilbe?

Give astilbe plants plenty of room for air circulation. 12-18” apart.

Astilbe Plant Care and Maintenance

Once established, most perennials require very little routine care and maintenance.

 

How Often Should I Water Astilbe?

For many perennials, average rainfall is sufficient to keep the plants healthy.  Supplementation may be necessary in droughty conditions.

New plantings should be monitored regularly to ensure that the soil is consistently moist.

Astilbe plants prefer moist locations. Under hot, dry conditions, the plant will begin to wilt and cease flowering.  In these cases, supplemental watering is necessary to keep a constant moisture level.

Mulch around the plant will help to lock in moisture.

 

Should I Fertilize Astilbe?

Most perennials do not require a specific fertilization regiment.  Fertilizing decisions should be based on a soil test.  If a soil test cannot be obtained and you feel that your perennial bed would benefit from fertilization, keep it light.  Work in a small amount of a low nitrogen fertilizer, such as 5-10-5 around the plants in the early spring and once or twice at six-week intervals.

Astilbe is a heavier feeder than most perennials and will benefit from a high nitrogen fertilizer added in the fall.

Fertilize the soil around the plant at least 6” from the plant base. Irrigate into the soil.

 

Additional Care Instructions

Divide plants every 3-4 years in the spring.

Deadhead spent flowers if you don’t want them to self-seed.

Cut the plant back in the spring.

Astilbe Diseases

The most common diseases associated with this plant include bacterial leaf spot, cercospora leaf spot, and powdery mildew.

Astilbe Pests

The most common pests associated with this plant include black vine weevils, Japanese beetles, tarnished plant bug, and whiteflies .

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