Description and Overview:
Many Persicaria share 2 similar features: showy leaves and an aggressive nature. Persicaria polymorpha, or Giant Fleece Flower, doesn’t have showy leaves, but you’ll never miss them. And it tends to be quite well behaved in the garden. It blooms in early summer and goes on until fall, getting taller and taller along the way.
Although Giant Fleece Flower looks like a shrub, it grows like a herbaceous perennial, dying back to the ground in winter.
However it makes up for it by quickly growing upwards of 6 ft. tall and almost as wide, the following season. Giant Fleece Flower stays in a well-behaved clump and rarely seeds or spreads by rhizomes. It is widely adaptable and requires little maintenance.
Persicaria polymorpha is sometimes confused with Polygonum cuspidatum or Japanese Knotweed, which is considered an invasive. I haven’t seen anything to suggest that Persicaria polymorpha should be grown with caution, but please let me know if you do.
- Leaves: Dark green, alternate pointed leaves have slightly serrated edges. The stems are sturdy, but may need some support by the end of summer.
- Flowers: Astilbe-like white plumes are popular with butterflies. The late season seed heads are also attractive.
Persicaria polymorpha, Syns: Bistorta polymorpha, Polygonum polymorpha
Giant Fleeceflower, White Fleece Flower, White Dragon
Giant Fleece Flower is reliably hardy in USDA Hardiness Zones 5 - 9.
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 5 - 6 hours of sun per day. Too much shade can make this very tall and top heavy plant floppy.
It can take a year or two to reach its mature size, but once it does, expect a bushy 4 - 6 ft. (h) x 4 - 8 ft. (w). It will bend slightly toward the sun, but should not need staking.
The flowers start in early summer, (May-June) and peek shortly after. The plumes will persist until fall, when they then produce attractive seedheads.
I don’t know of any cultivated varieties of Persicaria polymorpha.
Because of its size, Giant Fleece Flower will make a statement anywhere in the garden, but it’s white plumes make it especially useful for a partial shade garden. It’s great for any border that needs a vertical accent and also works well as a screen or to block a view of something like an air conditioning unit. Just be sure to give your plant plenty of room. It will fill out quickly.
- Soil: This plant is easy to grow and widely adaptable. It can tolerate dry periods and is not particular about soil pH.
- Planting: Giant Fleece Flower is generally grown from divisions. I have never seen seed for sale. It can be hard to find in nurseries but ask for it. The young plants don’t look like much, but a small clump with quickly fill out and blossom.
Giant Fleece Flower requires very little maintenance. It has average water needs and will adapt to most soils. Although it enjoys moisture, once established it is moderately drought tolerant. I have never given mine any supplemental water and it has never disappointed me.
Cut back the old, dead foliage in early spring, before new growth starts. You could probably prune it back in the fall, if you prefer, but It looks so good in the fall that I leave it.
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 like asters,
No regular deadheading is required, to keep it blooming. As the plumes age, they will turn a pinkish mauve and eventually develop seedheads.
Pests & Problems:
There are no known problems of Giant Fleece Flower. It really is very easy to grow.