How to prepare astilbe plants for winter

Astilbe is an herbaceous perennial for gardeners in USDA hardiness zones 4 through 8 that grows from thick, tuberous roots called rhizomes.

It thrives in shady areas of the garden where the soil is slightly acidic, organically rich, moist and well-drained.

Feathery, feather-like flowers in vibrant shades of pink, red, purple and white add rich color to the late summer garden.

The flowers add vertical interest as well, rising above a basal mound of deeply serrated, fern-like foliage, which ranges from about six inches to three feet across, depending on the variety.

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Our guide to growing astilbe covers everything you need to know to cultivate this attractive ornamental flower in your garden.

In this article, I outline five steps you can take at the end of the season to promote the healthy return of your astilbe plants each year.

this is easy. let’s get started!

winding down

As astilbe flowers slowly fade, their spiky flowers remain attractive, drawing the eye upward, above the bronze basal foliage of autumn.

Even when they are completely brown and dry, they add depth and texture to the fall garden.

Not only are the flowers still pleasant to look at as the growing season draws to a close, their seeds provide valuable late-season nutrition for wildlife.

And when they stay in place all winter long, their delicate forms look like fairies dancing on snow.

However, while their skeletal remains can provide winter garden interest, there are better ways to care for your plants at the end of the season than simply letting them stand in place.

Let us now learn about them.

astilbe winter care

While astilbe is a cold-hardy perennial, a particularly harsh winter can challenge its survival skills, especially if the plant is not in the best of health.

Photo by Dominicus Johannes Bergsmaa, Wikimedia Commons, via CC BY-SA. Cropped.

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To give it every opportunity to return with vigor each spring, you’ll want to assist with these five proactive steps: divide, cut back, water, fertilize, and mulch.

Come find out how easy they are!

1. Divide and Transplant

One of the first considerations as the growing season approaches is whether or not you need to divide your plants.

Those with three to four years of growth who are large enough are good candidates.

Our guide to propagating astilbe by division has all the details, but here are the basics:

After a plant has finished blooming, four to six weeks before the average first frost date, dig over and under it with a long-handled spade.

To avoid injuring the rhizomes below, use your foot to push the spade down to its full depth, about six inches away from the leaf mound.

You’ll need to dig 10 to 12 inches deep, then lift the mound of earth, roots and all, into the ground.

Use your hands to gently separate the roots, dividing the large clump into several individual rhizomes, each with foliage attached.

After digging up your plant and separating it into several rhizomes, you can replant the main section in its original location. You can also move it as desired, perhaps to a spot in the garden with more shade or better drainage.

You can plant divisions in new locations one to three feet apart, depending on the mature dimensions of your particular variety.

Alternatively, you can pot the divided sections in containers filled with potting medium to store over the winter months.

If you choose to plant them in a pot, store them in a cool, dark place with screening to prevent rodent damage.

Keep the soil moist, but not wet, throughout the winter months.

Transplant the divisions into the garden in early spring after all danger of frost has passed.

2. Label and Cut Back

Whether or not you choose to divide your plants, you will need to cut them back for their winter dormancy.

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Be sure to mark their locations as the flowers begin to fade in fall, and before you cut them into short stems.

I’d be ashamed to tell you how many times I’ve accidentally dug up perennials or planted over bulbs because I forgot they were there.

You don’t need to be fancy – popsicle sticks and a waterproof marking pen will work.

Next spring, when new shoots sprout up everywhere, you’ll be glad you did!

After blooming has finished, use clean, sharp pruners to cut each stem back to a height of about three inches.

Use dried flower stalks in decorative arrangements, or discard them on the compost pile. Do not leave garbage in the garden.

While it may seem tempting to leave dry stalks for winter interest, rotting plants invite disease and rodents that can do root damage.

Also, stems damaged by wind or heavy rainfall can result in damage to the roots below.

3. water

Keep the soil moist around new divisions to help them establish strong roots before the first frost and before the onset of winter dormancy.

In the absence of rain, water all other astilbe plants at least once a week until the first frost. Just because the growing season is over doesn’t mean it’s time to cut off the water supply for this moisture-loving plant.

In addition, experts at Colorado State University Extension recommend watering perennials during dry winters to prevent root damage.

You can give your astilbe an occasional drink when the ground is free of snow and the air and soil temperatures are at least 40°F.

Plant tissue that contains moisture is less likely to be damaged by cold weather, and wet soil holds more heat than dry soil.

4. Fertilizing

Perennial astilbe plants crave phosphorus, and they benefit from spring and fall fertilizer applications.

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Know the date of the first average frost for your area, and in late fall, while the ground is still soft, apply a slow-release 5-10-5 (NPK) product, according to package directions. You want to fertilize late enough so that warm temperatures don’t encourage new growth before winter.

Well-nourished plants are better prepared to survive the winter.

5. Mulch

Another way to promote the health of your astilbe during the coldest months is to apply a two-inch layer of mulch.

This blanket of organic matter protects the crown of the plant, the place where the leaves meet the roots.

The best time to apply mulch is after the ground has frozen, to avoid potential root damage from burrowing rodents or moisture build-up in hot weather.

Excellent choices are compost, shredded leaves, or humus that decompose slowly over time, feeding and insulating the roots, improving drainage, and aiding in moisture retention.

In early spring, before new shoots appear, remove the old mulch, toss it on the compost pile, and add a fresh layer of organic material.

an ounce of prevention

Now that you know what it’s like to prepare plants for cold hardiness, you may be debating whether or not it’s worth the time and effort.

After all, they’re wired to survive, right?

I look at it this way. Winterizing astilbe is like buying insurance. It can’t hurt, and adds value in the long run.

Since healthy perennials have the best chances of survival, a little winter care can contribute to their triumphant return each spring.

Add these steps to your garden planter today, and grow your best astilbe flowers ever.

Are you growing astilbe in your garden? Do you have any winter care tips to share? Let us know in the comments below!

And for more on winter gardening, check out these guides ahead:

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