As gardeners, we aim to provide beauty to our world and sustenance to the many insects that live around us. We are always on the lookout for ornamental plants that attract pollinators and look gorgeous too. Thus, we dedicate this article to astilbe care: everything you need to know about it and how to grow it in your own shade garden.
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Astilbe has plume-like flowers and glossy green foliage that brightens up the flower garden. It’s a superb choice because it’s virtually trouble-free and easy to grow astilbe. Since it’s one of the best shade-tolerant plants you can plant astilbe in porch planters, under trees, and along part shade borders to add interest to your space.
Not only do they attract bees, but butterflies and hummingbirds love the plumage and this compact plant is resistant to deer and rabbits. Plus, they look great when planted with other ornamentals such as peonies, daylilies, and many iris varieties.
The name astilbe means “without brilliance”, but because of hybridization they are anything but dull in these modern times. You can find a variety of colors within this species that are related to hydrangea and bergenia. Now that you are as excited as we are about astilbe, let’s go into more detail about this lovely ornamental.
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Quick Care Guide
All About Astilbe
The botanical name is Astilbe spp. and there are at least 16 astilbe varieties of this herbaceous perennial. Other common names are false goat’s beard and false spirea. They are native to Eastern Asia and North America and are known for their beautiful foliage. Gardeners especially love the contrasting deep purple to magenta flowers.
They have fern-like foliage with dark green leaves with thick stems and showy flowers that range in color from white to purple. Bridal Veil astilbe showcases pure white flower spikes with contrasting dark green foliage. Each plume has multiple tiny flowers, with early blooming from early summer into early fall. The ideal location for these ornamentals is in the shade garden where they are protected from hot weather- avoid planting in full sun.
You can grow different varieties to receive a multitude of colorful blooms throughout the summer. Or for a compact version that grows to a max of 2 feet tall is the Chinese astilbe (Astilbe chinensis). Since astilbes are a symbol of patience and dedication, they are frequently given to others as a declaration of love.
Planting Astilbes
The best time of year to plant astilbes is the spring once the danger of frost has passed. If you are dividing an existing astilbe, you can do this in the spring or fall when the plant isn’t putting too much energy into growing.
You’ll want to pick a location that has partial shade to full shade. If you choose a location in full sun, your astilbe may not thrive if your environment is too hot. However, if you plant astilbe in full shade it may not receive enough light to produce its brightly colored flowers, but it will have attractive foliage.
Another option is to grow astilbe in containers and garden beds, as long as it receives plenty of moisture and the soil drains well. Providing nutrients throughout the season will also ensure they remain attractive. You can grow it from seed, buy a plant from a local nursery, or divide existing plants.
Care
Now that you have a better idea about this shade-loving perennial, you may wonder how and if you can grow the astilbe plant in your own shade garden. This section covers all the growing requirements of astilbe to get you started.
Sun and Temperature
Generally, astilbe prefers light or part shade but will tolerate full sun in northern zones as long as they get shade in the afternoon. The dark green foliage will grow well in deep shade but in order to get lovely flowers, they will need at least 4-6 hours of sunlight per day.
Depending on the variety, the growing zones for this ornamental are USDA zones 3-8. That being said, the ideal growing temperature is between 65 and 75 degrees Fahrenheit. They don’t thrive in an environment that experiences extreme cold or heat. In the winter months, provide a layer of mulch around the crown to protect it and the roots after you have pruned it for the season.
Water and Humidity
Water your astilbe in the morning to give it plenty of moisture for the warmth of the day. You’ll want to keep the soil moist, but not soggy – they dislike it when the soil becomes dry and you will know this if the leaves curl and droop. Astilbe is not drought tolerant, but some varieties such as the Chinese astilbe (Astilbe chinensis) have better drought tolerance than others.
Water deeply at least once per week (more often if it is especially hot), and apply mulch to help hold in the moisture- dry soil will affect the plants. Water at the bottom of the plant to prevent water from splashing on the foliage, which could encourage fungal diseases. Continue to water until the ground freezes and then prepare the plant for winter.
Soil
Astilbe plants prefer well-drained soil, high in organic material. The organic matter improves soil moisture and prevents it from drying out during hot summer months. They do not thrive in heavy, clay soils and prefer a slightly acidic pH of 6.0. If your soil contains more clay, add extra organic content such as peat moss, perlite, or coarse sand to improve the drainage.
Fertilizing
Astilbe plants are heavy feeders, and will need plenty of nutrients throughout the growing season to remain healthy and to produce beautiful flower heads. The best time of year to fertilize is in the spring with a slow-release balanced organic fertilizer that has an NPK ratio of 3-1-2 (nitrogen, phosphorus, potassium). Amend the garden soil regularly through the season with compost, and in the late summer feed with a high nitrogen fertilizer.
Pruning
As the flowers fade in the fall, you can leave them in place for winter interest if you live in a warmer climate. For those that experience a harsher winter, we recommend pruning your astilbe plants to help them survive the cold months. Cut all the foliage off within 3 inches from the top of the soil. After the first hard freeze, mulch around the plant to protect the roots. New foliage will grow in the spring.
Propagation
There are three methods for propagating astilbe: starting astilbe seeds, dividing existing plants, or by stem cuttings. Each one has its advantages and disadvantages with some being more preferred over others.
Starting seeds is a fun method, but will take the longest because astilbe are relatively slow-growing plants. You can collect seeds from any current astilbe plants you have, but aged seeds have the highest germination rate. Alternately, purchase seeds from a local seed company, starting them indoors at least 8 weeks before the last frost. You want your transplants to be large enough to tolerate outdoor temperatures, usually late spring.
Mature astilbe plants benefit from division, so if you already have some in your garden, division is a great option. Divide either in the early spring or late fall when the plants aren’t putting a lot of energy into growing. Water the existing plant generously to make it easier to dig up the root ball. Once the root ball is exposed, divide clumps into sections. Dig holes that are double the size of each section to be planted and amend the soil with compost. Water the divisions well to prevent shock.
The last method of propagation is by stem cuttings, but it is the least popular. This can be done anytime during the growing season, but choose stems that are free from flower buds. Cut the stem above a leaf node, remove ⅓ of the lower leaves and place the stem into prepared soil or root them in a container. Keep the cutting soil moist but not soggy and allow at least 3 weeks for the plant to root.
Troubleshooting
There is always the potential for growing problems, pests, or diseases when growing ornamentals. This section will cover common issues and potential concerns with ideas on how to prevent and treat them.
Growing Problems
Astilbe needs moist soil and plenty of nutrients to remain healthy. The most common growing problem is the soil drying out, which will cause the leaves to curl, turn brown, and then die off. Provide frequent watering when the weather is hot. Sometimes astilbe won’t bloom if they aren’t getting enough light, transplant them to an area that receives more sun.
Another issue is not providing enough nutrients since astilbe is a heavy feeder and won’t bloom unless they have plenty of reserves to pull from. Follow the recommendations for fertilizing and watering as mentioned earlier in the article to get the best results.
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.
Frequently Asked Questions
Q: Do astilbe need to be cut back in the fall?
A: Yes, in late autumn cut back the stems to 3 to 4 inches above the soil level. Cover the roots with mulch to provide protection during the winter months. However, do not mulch until the first freeze to prevent root rot and to deter rodents from taking residence.
Q: When should I prune astilbe?
A: Unlike other flowering plants, dead-heading astilbe won’t encourage new flowers to grow. Trim off old flowers as they die throughout the season or leave in place if you prefer the look of the dried flowers. Then prune the whole plant back in the fall to prepare for winter.
Q: How do you keep astilbe blooming all summer?
A: Provide plenty of nutrients to this heavy feeding plant. In the spring or early summer feed a slow-release fertilizer, amend the soil regularly through the season with compost, and in the late summer feed with a high nitrogen fertilizer. Also, do not place them in an area that receives full sun without any afternoon shade.
