How To Make Sure Your Astilbe Survives The Winter

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How To Make Sure Your Astilbe Survives The Winter

Astilbe plants are some of the best flowers you can have in your garden. Despite their name, which means “without brilliancy”, they are actually quite beautiful. These plants have pyramidal panicles that come in white, scarlet, or lavender colors. They are also easy to take care of, making them a great choice if you want shade-loving, moisture-loving plants.

Astilbe plants are moderately cold-tolerant and can be grown in USDA zones 4 to 9. However, they require winter care to produce healthy blossoms in the next season. While they can withstand snow, the temperature should not drop below -28 degrees Celsius (-18.4 degrees Fahrenheit).

The most important thing to remember when growing astilbe plants is to keep the soil moist. This is especially true for container-planted astilbes, which can be deprived of the soil’s natural insulation. When the soil cools beyond 15 degrees Fahrenheit, the roots can be exposed to cooler air temperatures, leading to winter injury. Therefore, it’s essential to move the containers indoors to a frost-free location like a garage or a shed. You may also want to wrap them in thermal sheets or plastic straw layers to provide extra protection.

Pre-winter astilbe care

Person dividing astilbe

plantersplace/YouTube

Overwintering astilbe plants requires some fall prep. If the flowering plant is aged between 1 and 3 years and has grown considerably, divide it at least four weeks ahead of the first frost to improve its flowering come spring. Separate its rhizomes and plant them 1 to 3 feet from the mother perennial. Otherwise, prune the herbaceous plant to three feet above ground once it stops blooming.

Consider keeping the dead inflorescence on, as it serves as a picturesque background for your snowman. Besides, if you enjoy maintaining an animal-friendly lawn, it can double up as food and harborage spots for hungry critters. But if your cultivar is prone to self-seeding, remove the spent blooms—it won’t encourage new flowers—and add them to your compost pile or flower arrangements. Meanwhile, feed the plant a phosphorus-rich fertilizer, such as a granular 5-10-5, when it’s sufficiently cold not to stimulate growth. Continue deeply soaking your astilbes every week until the soil freezes.

Overwintering astilbe plants

Person watering astilbe plant

galsand/Shutterstock

Winters can’t stop the astilbe plants from craving water. So, irrigate them around noon at least once or twice a month when it gets too dry—preferably when it’s over 40 degrees Fahrenheit with no signs of snow—lest they desiccate and suffer root injury. Water more if the area is prone to dry wind action. You can keep your flowering perennials happy by mulching the soil. Spread a two-inch-wide layer of shredded leaves, compost, or humus around the roots to retain moisture and provide winter insulation. Do so only when it’s freezing cold, or the soil may become waterlogged, causing root rot.

When temperatures dip below 20 degrees Fahrenheit, shield the ground-planted astilbes with brushwood and bubble wrap the containers, although blankets, burlaps, and their ilk work, too. Even better, move the pots to a dark, sheltered, cold area. Finally, add a screen to keep pests away. Around early spring, right about when they start growing new stems, replace the mulch. Also, be wary of late spring frosts, as they can damage your plant.

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Dr Heidi Parkes

By Dr Heidi Parkes

Senior Information Extension Officer QLD Dept of Agriculture & Fisheries.