Astilbes are one of the easiest perennial flowers to grow. They have long-blooming, plume-like flowers in soft shades of white, pink, and red, and the flowers are held on tall, stiff stalks above the airy foliage. Virtually pest-free, they can light up the shade garden or soften a sunny spot, and they are very low maintenance.
The Astilbe genus contains at least 18 perennial species native to Asia and and North America, but the types most common in gardens are cultivars of Chinese astilbe (Astilbe chinensis) or cultivars of a hybrid known as A. x arendsii , creating by crossing A. chinensis, A. thunbergii and A. astilboides.
You can plant Astilbe in either spring or fall but try and avoid planting in the hottest part of summer. If you must plant then, keep the plant well watered until you see new growth emerging.These are relatively slow-growing plants, but once established they will bloom for many years before needing division.
|Common Names||Astilbe, false spirea, false goat's beard|
|Plant Type||Rhizomatous flowering perennial|
|Mature Size||6 inches to 2 feet tall; 6-inch to 5-foot spread (depends on species)|
|Sun Exposure||Partial shade, full sun|
|Soil pH||6.0 (slightly acidic)|
|Bloom Time||Spring to summer|
|Flower Color||Pink, red, and white|
|Hardiness Zones||3 to 8 (USDA)|
|Native Area||Mountain ravines and woodlands in Asia and North America|
How to Grow Astilbe
Astilbe seed is available, but it can be difficult to germinate. It's easiest to start with a plant or division. Even a small plant will quickly fill out and perform well in its first year. In hot, dry climates, they need to be planted in the shade and/or given plenty of water.
Different varieties will bloom anywhere from mid-spring to late summer. If you plant different types of astilbe, you can prolong the bloom almost all season. The plumes remain in flower for several weeks and continue to look good as they fade and dry on the plant. No deadheading is needed since they will not bloom again.
Astilbe plants grow best in part shade but can also grow in full sun or full shade. Astilbe will bloom in full shade, but the plants prefer some sunlight to achieve their full size. In hot weather and dry soils, their foliage will burn in full sun; here, some relief from the afternoon sun is mandatory.
Astilbe plants prefer slightly rich, moist soil, with a slightly acidic soil pH of around 6.0.
The warmer the weather, the more moisture astilbe plants need, especially when situated in full sun. They do not handle prolonged periods of drought well; the leaves will brown and dry, and if left dry too long, the plants will die.
Temperature and Humidity
Astilbe plants are tough and can survive winter, even in harsh climates. After the first hard frost, put down two inches of mulch around the stem to regulate the soil's temperature.
Astilbe plants need phosphorus to bloom, so choose a fertilizer with the makeup of 5-10-5 or 10-10-10. Rake the fertilizer into the soil two weeks before you plant, or sprinkle a few granules onto the soil after the astilbe has been planted. Once the plant is established, fertilize every spring when the soil is moist but the leaves are not.
Extremely little maintenance is required of astilbe plants. The flower heads will dry on the plant and remain attractive for many months. The flowers can be cut whenever they start to look ragged, or left up for winter interest and cut back in the spring.
Divide astilbe plants every four to five years to keep the plants healthy. In ideal conditions, Astilbe plants can grow quickly and require more frequent division. Keep the plants well-watered after replanting and they will re-establish themselves quickly.
Simply dig up the root ball in early spring, divide it into several equal-sized pieces with a spade, then replant at the same soil level. Water well immediately after planting the pieces.
Common Pests and Diseases
Astilbes are virtually trouble-free, bothered by few diseases or insects. The tender, new growth may be nibbled on by groundhogs or rabbits, but once the plants have filled out, they typically don't suffer any long-term damage.
Astilbe is valued for bringing great long-lasting color to part shade borders, where tall colorful flowers are few. In addition, Astilbe provides a nice textural contrast to plants with large, broad leaves such as heuchera, hosta, and Ligularia. Astilbe can also be grown in containers.
Varieties of Astilbe
There are new varieties introduced every year and recently along with newer breeds with darker foliage, too. Some established standards include:
- Astilbe x arendsii 'Bridal Veil': Mid- to late-season bloomer with full white plumes
- A. x arendsii 'Fanal': Blooms early with blood-red flowers on bronze foliage
- A. x arendsii 'Rheinland': Another early bloomer in a rich pink; very hardy
- A. chinensis taquetii 'Purple Candles': Deep purple, chenille-like plumes
- A. chinensis 'Visions in Red': Compact plant with bronze foliage and deep red flowers