How to Grow Giant Fleece Flower

Giant fleece flower shrub with tall stems with large pointed leaves with white plumes

The Spruce / Evgeniya Vlasova

In This Article

Native to Asia, the giant fleece flower looks like a shrub but grows like a herbaceous perennial, dying back to the ground in winter. An often-overlooked landscape plant, it grows quickly, reaching upwards of 5 feet tall and almost as wide by the following season. The giant fleece flower stays in a well-behaved clump and rarely seeds or spreads by rhizomes, making it widely adaptable and necessitating little maintenance.

Giant fleece flowers have dark green, pointed leaves with slightly serrated edges. The stems are sturdy but may need some support by the end of summer. Its astilbe-like white plumes are popular with butterflies and even the late-season seed heads are also attractive. For best results, plant in your landscape in early spring.

Botanical Name Persicaria polymorpha
Common Name Giant fleece flower, knotweed, white fleece flower
Plant Type Herbaceous perennial
Mature Size 3–5 ft. tall, 3–4 ft. wide
Sun Exposure Full sun
Soil Type Moist but well-drained
Soil pH Neutral to acidic
Bloom Time Summer
Flower Color White
Hardiness Zones 4–9 (USDA)
Native Area Asia
Toxicity Non-toxic

Giant Fleece Flower Care

Giant fleece flower is generally grown from divisions, so you probably will not find seed for sale. Plants can be hard to find in nurseries, but it never hurts to ask. You may have the best luck by asking around local gardening groups and seeing if one of your fellow gardeners will give you some of theirs. The young plants don’t look like much, but a small clump will quickly fill out and blossom.

Once your giant fleece flower reaches maturity, expect a bushy plant with exceptional height and spread. It will bend slightly toward the sun, but should not need staking. The flowers start in early summer and peak shortly after. No regular deadheading is required to keep it blooming. As the plumes age, they will turn a pinkish mauve and eventually develop seedheads.

Because of its size, giant fleece flower will make a statement anywhere in the garden, but its white plumes make it especially useful as a border plant to add vertical interest. It also works well grouped with several together to form a screen or block a view of something like an air conditioning unit. Just be sure to give your plants plenty of room, as they will fill out quickly.

Giant fleece flower stems with small white plumes surrounded by pointed leaves

The Spruce / Evgeniya Vlasova

Giant fleece flower shrub with feathery white plumes on tall stems

The Spruce / Evgeniya Vlasova

Giant fleece flower shrub with white flower plums on tall stems with pointy and serrated leaves

The Spruce / Evgeniya Vlasova

Light

You can grow giant fleece flower in full sun to partial shade, but you'll get the best flowering if the plants get at least five or six hours of sunlight per day. Too much shade can make this very tall and top-heavy plant floppy.

Soil

Giant fleece flower is easy to grow and widely adaptable to a variety of soils. That being said, it's typically happiest in a mixture that is moist but well-draining. It can tolerate dry stints periodically (though shouldn't be kept that way for an extended period of time) and is not particular about its soil pH.

Water

Water your giant fleece flower plant once a week throughout its growing season, and throughout the summer, increasing your cadence if necessary due to especially warm or dry weather. Additionally, giant fleece flower can tolerate slightly boggy soil, making it a good option for planting near a lake, pond, or stream. When watering your plant, aim the stream of water at the base or roots of the plant in order to avoid fungal diseases in its dense foliage.

Temperature and Humidity

Giant fleece flower is a reliably hardy perennial in USDA hardiness zones 4 to 9. It's tolerant of heat, humidity, and moderately tolerant of drought once it has been established in a garden.

Fertilizer

Fertilizing your giant fleece flower plants isn't necessary. In fact, doing so can actually decrease the number of blooms that it produces. If you feel like your plant needs a boost, you can amend the soil with some organic matter.

Pruning Giant Fleece Flower

Giant fleece flower plants require very little maintenance in order to thrive. Cut back the old, dead foliage in early spring, before new growth starts (the thick stems are hollow and cut easily). You could prune it back after the end of summer if you prefer, but it looks so good in the fall that you may want to keep it standing. If you want a shorter, bushier plant that blooms later in the season, you can shear the entire plant in late spring, as you would with other fall bloomers such as asters.

Propagating the Giant Fleece Flower

You can multiply your giant fleece flower stockpile by propagation or division. Depending on your preference, you may find yourself working in different seasons—the plant should be propagated by division in the spring or fall, and propagated by seed in the spring.

Common Pests and Diseases

While giant fleece flower doesn't experience any issues with disease, you may find yourself contending with Japanese beetles munching on your plant throughout the season. The pests like the flowers of the plant, meaning they can feed on the giant fleece flower from bloom all the way through the fall. To treat the issue, you can either pick the beetles off the bush by hand (disposing of them in a bucket of soapy water) or spray the plant with an insecticide. However, keep in mind, doing so can also kill beneficial insects, too.