Dictionary of Flowers: Astilbe (False Spirea)

Beautiful raspberry-red Astilbe flowers. Image used under a Creative Commons licence with the kind permission of Dan Kristiansen and Flickr
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Beautiful raspberry-red Astilbe flowers. Image used under a Creative Commons licence with the kind permission of Dan Kristiansen and Flickr

  • Astilbe
  • Common name: astilbe, false spirea
  • Family: Saxifragaceae
  • Category: Perennial in USDA zones 3-8, depending on species
  • Height: 24" and up, depending on species. 
  • Width: 18" and up, depending on species
  • Sun/shade
  • Blooms: early summer to summer
  • Growth habit: upright, vertical. Used as a thriller in container combinations
  • Maintenance: easy
  • Soil: average to fertile, moist, well drained. Water regularly if grown in containers. 
  • Garden uses: containers, mixed border, cutting garden, pond gardens
  • Diseases: mildew, rot, blight
  • Pests: aphids, spider mites, Japanese beetles

Astilbes are native to Asia and Europe's wooded areas. Their small flowers appear in large feathery plumes that grow six to twenty four inches long. Their leaves are smooth, glossy and fern like.

Flower colors range from white to pink, rose, red and shades of lavender. The foliage can be green or reddish green.

Most garden astilbe plants are hybrids.

Most astilbes prefer shady conditions and moist, humus rich soils. They can handle more sun if watered more frequently.

Mulching around the plant helps to maintain the moisture they need. A water retentive potting soil is helpful when growing astilbes in containers.

To achieve best bloom, they need a period of winter cold. 

They only require division if they become too crowded, every three to four years in spring or fall. If divided in spring, plant the divisions in the garden, but if divided in fall, pot them for planting after winter.

They are not repeat blooming, so deadhead them just to keep tidy looking.

Pale violet and mauve colors are common in False Spirea. Image used under a Creative Commons licence with the kind permission of Distant Hill Gardens and Flickr
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Pale violet and mauve colors are common in False Spirea. Image used under a Creative Commons licence with the kind permission of Distant Hill Gardens and Flickr

Astilbes are heavy feeders. They like a top dressing of compost in early spring. They need to be fertilized during summer months with a bloom boosting formula. After they stop blooming, apply nitrogen rich fertilizer once. 

Astilbes are available in nurseries in spring and early summer, as both plants and bareroot stock.

They are difficult to start from seed; germination rate is usually low. They can be wintersown.

Propagation is easier by division. 




Close-up of the lovely delicate petals. Image used under a Creative Commons licence with the kind permission of Tony Hisgett and Flickr
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Close-up of the lovely delicate petals. Image used under a Creative Commons licence with the kind permission of Tony Hisgett and Flickr

Astilbes can be affected by mildew, crown rot and blight. Apply fungicide as needed and improve drainage and air circulation. If pest problems appear, use insecticide only as required.

Popular varieties:

  • Astilbe Japonica hybrids - medium sized plants up to three feet. Bloom in midseason. Flower colors include pink, red, magenta, white, peach and violet
  • Astilbe simplicifolia hybrids - compact plants that bloom in early summer. White flowers
  • Astilbe arendsii hybrids – this group offers very little resistance to dry conditions. Early bloomer group, with varieties in several colors and heights
  • Astilbe chinensis hybrids - one to three feet tall varieties that bloom in late summer
  • Astilbe thunbergii hybrids - nodding flowers on two to three feet plants. They bloom in late summer
False Spirea growing wildly in clumps. Image used under a Creative Commons licence with the kind permission of Kristine Paulus and Flickr
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False Spirea growing wildly in clumps. Image used under a Creative Commons licence with the kind permission of Kristine Paulus and Flickr

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