Astilbe

Astilbe, genus of about 14 species of herbaceous perennials, in the family Saxifragaceae, native to eastern Asia and North America. Some species are known by the common names false goat's beard and false spirea. They are often grown in gardens for their erect, featherlike flower spikes of white, yellow, pink, magenta, or purple, which rise above clumps of fernlike leaves from mid- to late summer.



These hardyherbaceous perennials are cultivated by gardeners for their large, handsome, often fern-like foliage and dense, feathery plumes of flowers. They are widely adapted to shade and water-logged conditions, hence they are particularly associated with pond-side planting. They also tolerate clay soils well. Numerous hybridcultivars have been raised. Flowers of at least some Astilbe species have a strong and pleasant aroma.


Table of Contents


Height(Avg)

1 - 8 feet


Width-Circumference (Avg)

6 - 60 inches


Approximate pH

around 6.0


Types of Astilbe


Bridal Veil (A. x arendsii)


Astilbe bridal veil is an astilbe arendsii hybrid that got its name from the pristine white bunches of delicate flowers that spread stylishly over the dark green leaves, resembling a floral rendition of a bride’s veil. This type of astilbe blooms excessively during the months of June and July and with the blend of white and green hues, seem to come straight out of a fairyland.



The evenly-spaced branches bearing the feathery clusters make a fine addition whether you are a fan of an all-white garden or want to add some muted tones in your front or back yard for a well-balanced look. To double the beauty of bridal veil, consider planting them with other types of flowers such as Asiatic Lilies, Jasmines or Oriental Lilies.


Chocolate Shogun (A. thunbergii)



Traditionally there has been little variability in astilbes’ foliage, which generally ranges from light to dark green, sometimes with hints of red or bronze. ‘Chocolate Shogun’ is the result of new breeding that brings true, rich, chocolate-maroon foliage into the mix. What a welcome addition. Be sure to give this astilbe enough sunlight to keep that great color, as deep shade will cause the leaves to turn a muddy dark green. The midseason blooms are pale pink and not very showy, but it’s worth growing this one just for the foliage.


Delft Lace (A. chinensis)



Its attractive, deep red stems are topped with soft apricot-pink flowers in early summer, followed by long-lasting red seed heads. With waxy, blue-green foliage that takes on a slight burgundy glow in autumn, ‘Delft Lace’ looks great throughout the growing season.


Fanal (A.x arendsii)


This cultivar of A. x arendsii produces deep red flowers and lacy foliage that changes colors with the seasons. Although the foliage begins bronze with new growth, it will darken to a deeper shade of brown as the season progresses. It’s the perfect accent to a fall garden, growing to about 24 inches tall and 12 inches wide.



‘Fanal’ is prized for its use in cut flower bouquets. It does not need to be cut back in the winter as the foliage provides interest in the garden even after the flowers have long faded.


Hennie Graafland (A. simplicifolia)


A. simplicifolia plants tend to be smaller than other options, producing fine foliage and feathery blooms. ‘Hennie Graafland’ is a delightful pint-sized pick that’s well-suited to containers. This compact plant only grows to about 10 to 18 inches tall and 24 inches wide.



It is not the most drought-tolerant kind of astilbe you can grow. The soil should remain moist at all times, especially if you are growing in a container where the soil is prone to drying out more quickly. This plan produces showy plumes of pale pink flowers that are small and delicate.


Maggie Daley (A. chinensis)



A. chinensis ‘Maggie Daley’ is best known for its bright purple clusters of flowers that appear atop bright green foliage. It’s a late-flowering variety of astilbe, producing flowers toward the middle to end of summer. It grows to about 28 inches tall and 20 inches wide.

Although all types of astilbe varieties are known for their ability to attract butterflies and other pollinators, this variety has one of the best reputations for doing so.


Peach Blossom (A. x japonica)

Commonly known as Japanese Astilbe, the peach blossom variety is unlike any other type of astilbe flowers. This hybrid species (astilbe x rosea) is a member of the astilbe japonica family and comprises of deciduous plants that have a pyramidal shape.



A graceful clumping perennial, ‘Peach Blossom’ produces elegant plumes of pale pink flowers in the spring and early summer months. With glossy green divided foliage, this cultivar can be grown in full sun or partial shade. This cultivar grows an average of two to three feet tall and wide.


Pumila (A. chinensis var. pumila)


A. chinensis var. pumila is sure to brighten up your garden in late summer. A dwarf variety, it is aptly named, since pumila means “small” in Latin. This variety produces elegant, slender clusters of pink or purple flowers and fine fern-like foliage.



Only reaching mature heights of about eight to 12 inches tall and 12 to 16 inches wide, this cultivar won an Award of Garden Merit from the Royal Horticultural Society in 1993.


Red Sentinel (A. x japonica)



A. x japonica ‘Red Sentinel’ makes a serious impact when grown among other perennial plants. It offers eye-catching clusters of bright scarlet flowers that appear as early as the beginning of summer in lacy plumes. It grows in 18-inch-wide clumps that reach mature heights of more than two feet tall. This cultivar grows best in full shade to partial sun. It is a marvelous flower to choose if you are interested in cutting flower stalks to enjoy in a vase indoors.


Rheinland (A. x arendsii)



A. x arendsii ‘Rheinland’ has feathery pink blossoms and mounds of dark green foliage that give it a light, fairytale-like quality. It grows best in full or dappled shade. This variety grows to about 24 inches tall and wide.


Sprite (A. simplicifolia)



A. simplicifolia ‘Sprite’ is another cultivar that received an Award of Garden Merit from the RHS in 1993. It produces lovely flowers in coral pink. This is a dwarf type that is known for its tiny, delicate blooms. As you might guess from the plant’s name, this hybrid only reaches about two feet or so in both height and width at maturity. Perfect for borders and raised beds, this plant can also be grown in a container on the deck.


Sister Theresa (A. x arendsii)



A. x arendsii ‘Sister Theresa’ is a fast-growing variety. This cultivar grows from 20 to 24 inches tall and spreads just as wide, blooming early in the summer. ‘Sister Theresa’ is best known for her cotton-candy colored plumes and fine, dark-green foliage.


Straussenfeder (A. thunbergii)



Also known as ‘Ostrich Feather,’ this A. thunbergii cultivar has coral plumes of flowers that bloom in June and July. Most plants grow to about three feet tall and just one or two feet wide at maturity, with lovely dark green, mounded foliage. You may find that new foliage is tinged with bronze.


Visions (A chinensis var. visions)



A. chinensis ‘Visions’ is another feathery variety that produces blooms in shades of raspberry pink. It has bronze-green glossy foliage that contrasts nicely with its warmer blossoms. It grows to about 10 inches tall and wide. Like most Chinese astilbes, this variety is more tolerant of dry soil than some, but growers should still avoid allowing it to dry out as a rule. It also produces fragrant flowers, something that is not found with all varieties of astilbe.


Purple Candles (A. chinensis var. purple candles)



This plant can reach heights of three to four feet and features lovely purple flowers.Its flowers emerge violet-red, becoming paler with age in midsummer. This is a big, back-of-the-border astilbe, with coarse, dark green foliage. Its statuesque spires make a statement in the shade, and its A. chinensis genes give it more sun and heat tolerance than many other varieties.


Superba (chinensis var. tarquetti)



‘Superba’ (chinensis var. tarquetti) One of the tallest Astilbe varieties, expect the ‘Superba’ to grow as tall as four to five feet. The flowers are a lovely purple-rose color.


Irrlicht Astilbe (Astilbe × arendsii)



Irrlicht is an incredible garden plant that consists of lacy greens which eventually turn into bronze foliage when bloom time is over. These garden plants are shade-loving perennials that look a lot like the bridal veil astilbe, but unlike the latter which can grow in wet areas, this species prefers clay soils. Compared to other varieties, this type of astilbe is surprisingly quite drought-resistant and can also tolerate greater exposure to the sun.


Planting Astilbe


Astilbes prefer light to moderate shade. Deep shade will result in few and/or poor flowers. The plant requires well-draining fertile soil with compost or aged mature added compost. Also, ensure this plant gets constant moisture (without puddling). In summer, damp conditions are important. Plants that are stressed for water will have burned summer foliage and disappear in a season or two. They prefer a soil pH of slightly acidic to neutral.


When to Plant Astilbe

  • Pots of astilbes are available at garden centers in spring and early summer and should be planted as soon as possible.

  • Divide existing astilbe plants in early spring as soon as you see new growth.

  • When started from seeds, astilbes can be difficult to germinate. The resulting plants tend to be short-lived. Division is recommended to keep the plants producing.


How to Plant Astilbe


If you are planting bare-root plants, make sure the holes are twice as wide as the plants and 4 to 6 inches deep. Place the plants so that the roots are fanned slightly and pointing downwards, with the crown planted 1 to 2 inches below the ground level. Cover the roots with soil and press firmly. Water well.


For plants already growing in nursery pots at garden centers, loosen the soil to about 10 to 12 inches deep. Mix in a handful of compost. The crown (where roots and plant connect) should be just below the soil line. Back fill with soil removed from hole. Water well after planting.


Astilbe Care


Astilbe is valued for great long-lasting color in part shade borders, where tall colorful flowers are few. In addition, the lacy foliage of astilbe provides a nice textural contrast to plants with large, broad leaves such as heuchera, hosta, and Ligularia. It can also be grown in containers.


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.


Light


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, the foliage will burn in full sun; here, some relief from the afternoon sun is mandatory.


Soil


Astilbe plants prefer fairly rich, moist soil, with a slightly acidic soil pH of around 6.0.


Water


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. In the absence of rain, water astilbe weekly and deeply at the base, avoiding overhead watering. Keep the soil moist but not soggy.


Temperature and Humidity


Astilbe plants are tough and hardy plants that can survive winter, even in harsh climates. After the first hard frost, put down 2 inches of mulch around the stem to protect the roots.


Astilbe can grow in a moderately humid climate but in humid weather conditions, it can develop powdery mildew.


Fertilizer


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. Apply the fertilizer on the soil and avoid getting any on the leaves, especially when they are wet, as the fertilizer will stick to them.


Pruning and Propagating Astilbe


Pruning


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.


Propagating Astilbe


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. 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.

  1. Dig up the root ball in early spring and divide it into several equal-sized pieces with a spade,

  2. Replant at the same soil level. Water well immediately after planting the pieces.

  3. Keep the plants well-watered after replanting and they will reestablish themselves quickly.


Harvesting


Astilbes are wonderful cut flowers. Put them in a vase with fresh water. They last 4 to 12 days in a vase. Cut the main stem, which frees up the side shoots to develop. Cut the side shoots as desired.


Pests and Plant Diseases


Pests


The Asiatic garden beetle is common among many plants and you can see them emerging in June, with the highest populations arriving in July. The beetle is reddish-brown and they lay their eggs in the soil at the base of the plant. As the larvae hatch, they feed on the astilbe plant. They are active at night, so one way to rid this pest is to place light traps or to hand-pick them from your plants. Pyrethrins can help in the control of adult beetles, though they aren’t 100% effective.


Black vine weevil is another common pest seen attacking astilbes. The larvae also feed on the roots of the astilbe, causing them to become weak and eventually die. Adult black vine weevils are black and approximately ½ inch long with a beaded appearance to their thorax and long antennae. Place insect pathogenic nematodes in your soil as the first line of defense to kill the larvae that mature into grubs. Since the weevil doesn’t fly, apply diatomaceous earth on the ground for extra protection and for extreme cases consider a biological insecticide containing Beauveria bassiana, a species of fungus found naturally in the soil.


Diseases


Common diseases seen are leaf spots, powdery mildew, and wilt.


The fungal Cercospora species causes leaf spots. Spores are carried by the wind or transferred by splashing water (such as when you water your astilbe and the water hits the leaves or splashes onto the plant).


The infected leaf will develop tiny purple or maroon spots, which increase in size and eventually cause the leaf to fall off. It usually begins at the bottom of the plant and works upward. To prevent leaf spots, remove fallen leaves from around the plant and water at the base of the plant to prevent splashing. Sulfur and copper-based fungicides will prevent spores from erupting but won’t treat once the plant is infected. Remove any leaves that are affected and/or use an organic fungicide.


Powdery mildew is also fungal in origin and can be prevented the same way as leaf spots. Afflicted leaves appear to have been sprinkled with a white powder. If left untreated, the leaves will turn yellow and die. Prevention is the best measure for fungal diseases, but you can use an organic fungicide to treat it. However, if it is severe, remove the affected plant to prevent the disease from spreading.


Fusarium wilt is a pathogen that causes damage to the vascular system of the plant and there is no treatment. Your plant will display signs of not receiving enough water, like wilted and brown leaves. But the plant may exhibit signs only on one side. The leaves eventually hang down and dry up. Remove the plant, all the roots, and any soil the roots were in contact with because the pathogen can survive in the soil for long periods of time. Prevention is the best medicine, and some mycological additives are proving to be helpful in preventing fusarium in the soil.


Uses


Some species, particularly Astilbe rivularis, are used in traditional medicine. It can be used to treat inflammation, headache, bleeding during childbirth, chronic bronchitis, and cancer.


The leaves of Astilbe are used as a tea in Asia and some species do include a fruiting part that is eaten fresh.


Astilbe flowers are great to have in your garden to attract moths, flower flies, butterflies, and bees. By choosing plants that attract pollinators, you can help your entire garden thrive.

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