When to prune astilbe?

Astilbe Winter Care: How To Winterize Astilbe Plants

Astilbe is a tough flowering perennial that is hardy from USDA zones 3 through 9. This means that it can survive the winter in even very harsh climates. While it should survive for years, there are a few steps you can take to give it a serious leg up and make sure it survives the cold. Keep reading to learn about care for astilbe plants in winter and how to winterize astilbe.

Winterizing Astilbe Plants

Astilbe plants like to be kept moist, so it’s important to keep watering yours until the ground freezes. After the first hard frost, put down about two inches (5 cm) of mulch around the stem. This will help regulate the temperature of the soil and keep the roots moist through the winter.

Be careful not to put the mulch down until the frost, though. While the roots like to be moist, mulch in warmer weather can trap too much water and cause the roots to rot. Astilbe winter care is as simple as that – plenty of water before the frost and a good layer of mulch to keep it there.

How to Care for Astilbe Plants in Winter

When winterizing astilbe plants, there are a couple routes you can take with the flowers. Deadheading astilbe won’t encourage new flowers, so you should leave them in place through the fall. Eventually, the flowers will dry on the stalks but should stay in place.

When winterizing astilbe plants, you can cut all the foliage off, leaving just a 3-inch (7.5 cm) stem above ground. It makes astilbe winter care a little easier, and all new growth will come back to replace it in the spring.

You can also save the flowers for dry arrangements indoors. If you want, though, you can leave the flowers in place through the winter. They’ll dry out and provide some interest in your garden when most other plants have died back. You can then cut back all the dead material in early spring to make way for new growth.

Mistakes to Avoid when Growing Astilbes

Although astilbes are relatively easy to grow, they are a little different than some other varieties of perennial flowers. The ways that astilbe flowers differ from other perennials tends to cause many gardeners to make common mistakes when planning and caring for them.

Avoid Direct Sunlight

Unlike many other perennials, astilbes generally grow and thirve better in shaded areas rather than in direct sunlight. The astilbe flowers have above average water requirements for a perennial, and too much direct sunlight may cause the soil to dry out and cause your astilbe to wilt or die.

No Deadheading Required

Deadheading astilbe flowers has no positive effect at all and produces no new blooms or flowers. While many other perennials benefit from clipping faded blooms (deadheading) by actually encouraging new bloom and flower growth., your astilbe flowers will not benefit from this practice.

Avoid Overcrowding

Astilbe flowers are relatively resistant to most types of diseases; however, spacing your astilbe flowers too close together may result in powdery mildew being caused by fungi that thrive in overcrowded plant environments. So, make sure to space the astilbe flowers about 1 to 3 feet apart depending on the variety.

Deadheading for Extended Bloom

Let’s face it. Even the name is scary.

But deadheading, despite the ominous sound, is nothing more than trimming off spent flowers, keeping plants tidy, and ensuring maximum bloom time. Some gardeners worry that if done imperfectly, it might harm the plant. But unless you really whack away at it, it’s tough to kill or badly deform a plant by deadheading.

First and foremost, deadheading keeps your garden attractive. Nearly all flowering plants benefit from at least a little deadheading. When blooms start to fade, brown, curl, or otherwise look unattractive, that’s the time to trim them off, allowing the other flowers to shine.

Summer’s end is a great time to take a close look at your plants; find more tips for seasonal care here.

Which Plants to Deadhead?

You can often get a clue about which plants to deadhead and which to leave alone simply by watching them. If the flowers stay on the plant and become brown and unattractive, it’s time to deadhead.

Shrubby Plants with Many Small Flowers

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These include Coreopsis, feverfew, golden marguerites, Lobelia, sweet alyssum, smaller mums, Potentilla, flax, Aster, Gaillardia, and Ageratum. Trimming one flower at a time would be too time consuming, so instead, shear off with grass shears. Get as much of the flower stalk as possible. Avoid buds, but don’t worry about taking a little foliage off with the blooms — it’ll grow back.

Shrubby Plants with Large Flowers

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These include large marigolds, summer phlox, Astilbe, peonies, purple coneflowers, black-eyed Susans, daisies, annual and perennial Salvia, petunias, and zinnias. With hand pruning shears (also known as secateurs or pruning snips), cut off each flower individually, getting enough of the stalk so it doesn’t protrude awkwardly. It’s OK (and in the case of leggy plants, such as petunias, desirable) to take off a bit of the foliage, too.

Roses

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Not to be confused with pruning, deadheading roses means taking out only the minimum amount of stem to remove the flower. Make the cut at a 45-degree angle that slopes down toward the center of the rosebush. The cut should be located on a spot 1) that occurs after the first pair of leaves and 2) is directly above an outward-facing stem, that is, a stem that points away from the plant’s center.

Long-stem Flowers on Tall Stalks

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These include daylilies, larkspur, foxgloves, hostas, tulips, daffodils, Oriental poppies, and irises. Simply cut back each flower with hand pruning shears as close as possible to the spot where the stalk meets the leaves.

Bloom Longer if Deadheaded

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  • Hardy geraniums
  • Coreopsis
  • Petunias
  • Marigolds
  • Snapdragons
  • Begonias
  • Roses
  • Campanula
  • Blanket flowers
  • Delphinium
  • Zinnias
  • Sweet peas
  • Salvia
  • Scabiosa
  • Annual heliotrope
  • Geraniums (Pelargonium)
  • Tulips
  • Daffodils
  • Yarrow

No Need to Deadhead

  • Grasses
  • Sedum ‘Autumn Joy’
  • Melampodium
  • Impatiens
  • Most flowering vines
  • Most groundcovers
  • Crocuses and other “minor” spring-blooming bulbs
  • Wishbone flower (Torenia)

Other Ways to Extend Blooms

Image zoom Tulips will bloom longer if deadheaded.

Deadheading is just one way to stretch the bloom season. Try these other ways to make color last.

Set potted annuals in the garden and move them around to areas that need an instant color lift.

Plant late-summer and autumn-flowering bulbs in early to midsummer for lovely late-season bloomers.

Apply organic mulch (bark chips or shredded leaves) to stifle weeds and retain soil moisture. Organic mulches break down and improve soil, too.

Water deeply every three to four days while young plants are establishing themselves, then cut back to weekly waterings. Later in the season, water as needed when soil is dry.

Feed perennials monthly (spring through summer) with a fertilizer that’s low in nitrogen but high in phosphorus. Feed annuals every three weeks with a balanced (5-10-5) organic fertilizer.

Weed out any unwanted plants so flowers won’t have to compete for nutrients.

Remove rose suckers — the stems that grow below where the plant is grafted to the roots — right at the rose’s base as soon as you see them.

Propagate existing plants by dividing them or collecting seeds from one or two faded blooms that you don’t deadhead — the more the merrier!

Astilbe Care Guide: How to Grow False Goat’s Beard

Astilbe Care

Astilbes require a semi-shaded location in soil that does not dry out. Smaller varieties can be grown in containers but will need regular watering. The plants are perennials and will come back year after year. Most are hardy and will tolerate freezing conditions and snow. The plants will cope with most soil types, including acid soils, as long as the soil is not dry.

Light requirements

Most astilbes prefer semi-shade. They do not tolerate direct sun at the hottest part of the day. They do need some sun to flower well, but this can be as little as an hour of dappled light each day. This makes them the perfect flowering plant for shady conditions.

Water requirements

As woodland plants, they do need to be kept moist and will not tolerate drying out especially if they are in full sun. They will do well in relatively boggy areas of the garden such as by ponds and streams. However, if they are well watered they will manage in most conditions.

Soil requirements

Astilbes are suitable for all soil types, including acid soils, the only exception is dry soil. Some varieties will do okay in sandy soil as long as they have shade. If the soil is poor, dig in organic material, such as compost, to a depth of at least 20cm before planting. A mulch will help the roots stay cool and moist.

Fertilizer requirements

Refresh the mulch yearly. The mulch helps retain moisture and provides a natural fertilizer as it breaks down. A granular slow release flowering perennial fertilizer may be applied in spring to ensure plentiful flowers. Phosphorus will help the plant bloom well so choose a 5-10-5 or 10-10-10 fertiliser (the middle number is the phosphorus ratio).

Pruning advice

Astilbes do not need pruning. You can, however, tidy back the plant as required and cut back any old growth as the new growth begins to appear in spring.

Planting

Astilbe is often sold bare-rooted in the early spring. If you buy these plants, make sure you get them in the ground as soon as possible after buying so that they do not dry out. Keep them wrapped in moist newspaper until you can plant them. The plants will thrive in moist, humus-rich soil. Add potting compost or organic matter if the soil is poor.

When planting, ensure the hole is twice as wide as the plant and 6 inches (15 cm) deep. Fan out the roots into the hole and make sure the crown is an inch (2.5 cm) or so below the ground. This will prevent it from drying out. Backfill the hole and water well. Applying a mulch will keep the roots, moist, provide nutrients and repress weeds.

If you are planting astilbes that have been divided, you can plant them either in spring or autumn. Plant these 1-3 feet apart, depending on the variety.

After 3 to 4 years your plant may become overcrowded and congested. At this point, you can dig up the plant in late summer and divide it, then replant the divisions or put them in pots until they are more established ready for planting out in early summer of the next year (see Propagation for details on how to do this).

If you have an astilbe that is not thriving, and you think it needs a change of position, the best time to transplant it is in late summer or autumn. You can also divide the plant at this time if necessary.

Container-Grown Astilbe

Smaller varieties of astilbe can be grown in pots. They are useful for adding a splash of colour to a shady patio or seating area. Be careful that they are not in full afternoon sun as they will dry out and die. A little, dappled sunlight each day will help them flower, though.

Plant in a large container with good quality potting compost. Keep them well-watered as they hate having dry roots. During the growing season, a fortnightly application of soluble fertiliser will keep them healthy and flowering well.

Continuing Care

The essential thing to remember with astilbe is to keep them well watered and out of strong sunlight.

Unlike many flowers, removing flower heads will not result in more flowering. In fact, many people like to leave the seed heads on as they add extra interest and texture to the garden. Even after flowering is finished your plant will continue to provide attractive foliage. After the first frost, the leave will begin to turn yellow. You can cut back the plant at this time to keep it tidy or you can do this in spring when the new growth begins.

Winter care

Astilbe can cope with very cold weather. However, there are a few things to do ensure this is the case. Firstly, the plants hate to dry out, so continue watering them until the ground freezes. At this point, apply a mulch to the plant to help it cope with the cold.

While many people leave the dead flowers stems as winter interest they can be cut back to 5 cm above the soil in order to make it easier to apply a mulch.

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