Ornamental · Polygonaceae
Mountain Fleece
Persicaria amplexicaulis
Give it steady moisture and room to spread, and mountain fleece throws up red bottlebrush spikes from June to frost.
Full sun
Every 3–7 days
USDA 4–7
3–4 ft · 0.9–1.2 m
Overview
Mountain fleece is a tough, easygoing perennial that earns its keep with months of color. From June into October it sends up slim, red bottlebrush spikes above neat clumps of green foliage, and the show barely lets up. It belongs to the knotweed family but behaves itself, forming a clump that widens slowly rather than running wild.
This is a plant for the damp end of the garden. It thrives in average to wet soil, takes full sun where the ground stays moist, and shrugs off part shade. Hardy down to zone 4, it dies back each winter and returns reliably each spring, growing waist-high at 3 to 4 feet across.
Care asks little of you. Cut the old growth to the ground in late winter, divide a tired clump every few years, and keep an eye out for aphids and slugs. Deer and rabbits tend to leave it alone, which makes it a quiet workhorse in a border or beside a pond.
Care
The short version: full sun to part shade, in soil kept consistently moist. Cut it to the ground in late winter, divide the clump every 3 to 4 years, and give each plant 3 to 4 feet of room to fill out.
Light
Mountain fleece does best in full sun but happily takes partial shade or partial sun. The one catch is moisture: in full sun the soil has to stay damp, or the plant flags in the heat of summer.
Water
This is a plant that wants water. Keep the soil consistently moist, watering roughly every 3 to 7 days, and water more often in hot weather or strong sun. It even tolerates wet ground and the margins of a pond.
Soil
Plant it in average, medium to wet but well-drained clay or loam. It handles consistently damp conditions that would rot fussier plants, and it isn't picky about pH, growing across a wide band from 6.0 to 8.0.
Temperature
Mountain fleece is cold-hardy to a remarkable -29°F (-34°C) and comfortable up to about 86°F (30°C). It dies back in winter and returns each spring, so a hard freeze is no threat to an established clump.
Humidity
Outdoor humidity is whatever the weather brings, and the plant doesn't mind either way. What it really wants is moist roots, not damp air.
Feeding
Feed lightly. Work a balanced general-purpose fertilizer or some compost into the soil at the start of the growing season in spring and that's usually plenty. Go easy, since too much nitrogen produces soft growth that aphids love.
Pruning
Cut the whole plant back to the ground in late winter or early spring to clear the way for fresh shoots. Through summer, snip off the spent spikes to push out more bloom and curb self-seeding.
Repotting
Mountain fleece isn't a container plant, but it does need dividing every 3 to 4 years. Lift and split the clump when it loses vigor, hollows out in the center, or starts throwing fewer and smaller flower spikes.
Size & spacing
Plan for a clump that reaches 3 to 4 feet (91 to 122 cm) tall and just as wide. Give each plant a matching 3 to 4 feet (91 to 122 cm) of room so it can fill out without crowding its neighbors.
When to plant
Mountain fleece runs on a simple seasonal rhythm. Start seed indoors in late winter, set young plants out in spring after the frost or again in early fall, and the flower spikes carry from June all the way to October.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring (about 6-8 weeks before last frost)
- Plant: Spring after the last frost, or early fall
- Harvest: June to October
Hardiness
USDA hardiness zones: 4–7
Temperature: down to -34°C
Troubleshooting
Mountain fleece is a healthy plant with few real problems, so most of what you'll meet is chewed leaves or a storm-flattened stem. Match what you see below and act early, while the fix is still simple.
Curling new growth crawling with tiny insects
This is an aphid colony, the most common pest on mountain fleece. The bugs cluster on tender shoots and leaf undersides, sucking sap and leaving sticky honeydew behind. Blast them off with a strong jet of water, treat heavier patches with insecticidal soap, and let lady beetles and lacewings finish the job.
Fix:
- Spray plants with a strong jet of water to dislodge aphids
- Apply insecticidal soap or horticultural oil to affected growth
- Encourage natural predators such as lady beetles and lacewings
Holes and skeletonized patches chewed in the leaves
Two culprits chew leaves like this. Japanese beetles are the metallic copper-and-green ones you see feeding by day, while slugs and snails work overnight and leave slime trails near the soil. Hand-pick the beetles into soapy water each morning, set out iron-phosphate bait for the slugs, and clear away the damp debris where they hide.
Fix:
- Hand-pick Japanese beetles in early morning and drop them into soapy water
- Set out slug and snail traps or iron-phosphate baits
- Remove debris and mulch that shelter slugs and snails
Tall stems flopping or snapped after a storm
The tall flower stems take a beating in wind and heavy rain, especially on big clumps. Cut any broken stems back cleanly so they can regrow. Stake or use grow-through supports on exposed clumps, and where you can, plant in a spot that's sheltered from the worst of the wind.
Fix:
- Remove broken stems with a clean cut
- Provide staking or grow-through supports for tall clumps
- Site plants in a location sheltered from strong wind
Stray seedlings and clumps widening over the years
Mountain fleece self-seeds and spreads slowly by rhizome where conditions suit it, so new plants turn up near the parent and the clump creeps outward season by season. This is steady, not aggressive, and the plant is not invasive. Deadhead the spent spikes before seed sets, pull young seedlings you don't want, and lift and divide a clump that has outgrown its space.
Fix:
- Deadhead spent flower spikes before seed sets
- Pull or transplant unwanted seedlings while young
- Divide and reduce clumps that have spread beyond their space
Toxicity
Good news for anyone with pets or children: mountain fleece is non-toxic. The ASPCA doesn't list it, and horticultural references report no serious toxicity, so you can plant it freely in a garden that gets a lot of paws and small hands.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Mountain fleece is not on the ASPCA toxic list, so a curious cat that nibbles a leaf has nothing to fear beyond a brief bit of stomach upset from the roughage.
Dogs None
Dogs are safe around this plant. A mouthful of foliage might loosen the stomach for an hour, the way any garden greenery can, but it carries no real poison.
Horses Safe
No toxicity is documented for horses, and the plant is grazed without harm. It simply isn't a favorite, so most animals leave the tough spikes alone.
Rabbits Safe
Rabbits can browse it without trouble. The plant is even noted as rabbit-resistant, so they tend to pass it by in favor of softer plants nearby.
Livestock Safe
Cattle, goats, and sheep face no known danger from mountain fleece, and there are no records of it poisoning farm animals.
Birds Safe
Birds are in no danger here. The small seeds and foliage hold nothing harmful, and the plant is a benign part of a wildlife border.
People Safe
Mountain fleece is safe to have around children. It is grown purely as an ornamental and poses no poisoning risk if a curious child handles or tastes it.
No special handling precautions are documented; as with any plant, discourage pets from chewing ornamental foliage to avoid mild stomach upset.
Varieties
Mountain fleece comes in a handful of named selections that differ mainly in size and flower color. These two turn up most often.
Firetail
A popular cultivar carrying showy crimson to rose-red bottlebrush spikes from June right into October.
Golden Arrow
A compact pick that stays just 18 to 24 inches tall and wide, pairing golden-green foliage with cardinal-red summer flowers.
Companions
Mountain fleece pairs best with plants that share its love of moist ground, and worst with anything that wants to stay dry.
Plant near
Ornamental grasses: Their upright vertical texture contrasts with the fleece flower spikes in borders and meadow plantings with similar moisture needs.
Astilbe: Shares a preference for moist soil and part shade, providing complementary plume-shaped blooms in similar conditions.
Keep apart
Drought-loving Mediterranean herbs such as lavender: These prefer dry, lean soil, which conflicts with the consistent moisture mountain fleece requires.
How to propagate
Mountain fleece is simple to multiply, whether you split an existing clump, let it self-sow, or take a cutting.
DivisionEasy
Spring or fall · One growing season
Division is the easiest and most reliable way to make more mountain fleece. In spring or fall, lift the rhizomatous clump, split off healthy pieces, and replant them at the original depth. Each division settles in and fills out within a single growing season.
SeedModerate
Late winter to spring indoors, or self-sown outdoors · One to two growing seasons to reach flowering size
The plant self-sows freely, and you can also sow collected seed indoors from late winter into spring. Be patient, since seedlings take one to two growing seasons to reach flowering size. Keep in mind they may not come true, so seed-grown plants can drift from a named cultivar.
Stem cuttingsModerate
Late spring to early summer · Several weeks to root, one season to establish
You can also take softwood basal cuttings from non-flowering shoots in late spring or early summer. They root over several weeks and need a full season to establish, though most gardeners reach for division instead.
Myths
All knotweeds are dangerously invasive, so mountain fleece will take over the garden.
Mountain fleece does self-seed and creep outward slowly where it's happy, but it's expressly described as not invasive. It behaves nothing like its aggressive cousin Japanese knotweed, and a quick deadhead or division keeps it in bounds.
Mountain fleece is poisonous and unsafe to grow around pets and children.
It isn't listed as toxic by the ASPCA, and horticultural references report no serious toxicity concerns. It's treated as a fully non-toxic ornamental, safe for a garden shared with pets and kids.