Ornamental · Polygonaceae
Mountain Fleece
Persicaria amplexicaulis
Keep it in steady moisture with room to spread, and mountain fleece sends 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 one of those laid-back perennials that pays you back with color for months on end. From June into October it keeps sending up slim red bottlebrush spikes over neat green clumps, and it barely takes a break. Yes, it's in the knotweed family, but this one has manners, spreading into a clump that widens slowly instead of taking off.
This is a plant for the soggy spot most gardens have somewhere. It's happy in average to wet soil, takes full sun as long as the ground stays moist, and doesn't mind a bit of shade either. Hardy all the way down to zone 4, it dies back in winter and pops right back every spring, growing waist-high at 3 to 4 feet across.
Honestly, it hardly asks for anything. Cut the old stems to the ground in late winter, split a tired clump every few years, and keep half an eye out for aphids and slugs. Deer and rabbits tend to leave it be, which makes it a quiet, dependable pick for a border or a spot by the pond.
Care
The short version: full sun to part shade, in soil that stays consistently moist. Cut it to the ground in late winter, split the clump every 3 to 4 years, and leave each plant 3 to 4 feet of room to fill out.
Light
Mountain fleece is happiest in full sun, but it's perfectly fine in partial shade or partial sun too. The one thing to keep in mind is moisture, because in full sun the soil has to stay damp or it'll flag once summer heats up.
Water
This plant really likes a drink. Keep the soil consistently moist, watering about every 3 to 7 days, and step it up in hot weather or strong sun. It'll even put up with wet ground and the edge of a pond, so no worries there.
Soil
Give it average, medium to wet but well-drained clay or loam. It'll handle soggy conditions that would rot a fussier plant, and it's not picky about pH at all, growing across a wide band from 6.0 to 8.0.
Temperature
Mountain fleece is seriously cold-hardy, right down to -29°F (-34°C), and it's happy up to around 86°F (30°C). It dies back in winter and comes back every spring, so even a hard freeze won't bother an established clump.
Humidity
Outdoors, humidity is just whatever the weather hands you, and this plant couldn't care less. What it actually wants is moist roots, not damp air.
Feeding
Go easy on the food. 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 all it needs. Don't overdo it, because too much nitrogen makes soft growth that aphids just love.
Pruning
Cut the whole thing back to the ground in late winter or early spring so the fresh shoots have room to come up. Then through summer, snip off the spent spikes to coax out more bloom and keep the self-seeding down.
Repotting
Mountain fleece isn't a pot plant, but it does need dividing every 3 to 4 years. Lift and split the clump when it starts losing steam, hollows out in the middle, or throws fewer and smaller flower spikes.
Size & spacing
Plan for a clump that hits 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 whatever's next to it.
When to plant
Mountain fleece keeps to a pretty simple calendar. Start seed indoors in late winter, set the young plants out in spring once the frost's gone or again in early fall, and the flower spikes will keep going 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 that rarely gives you grief, so most of what you'll run into is a chewed leaf or a stem knocked flat by a storm. Just match up what you're seeing below and jump on it early, while it's still an easy fix.
Twisted baby leaves with little bugs bunched all over them
See tiny bugs bunched on the new growth? That's aphids, and they're the pest mountain fleece runs into most. They pile onto the soft shoots and leaf undersides, drink the sap, and leave a sticky mess behind. Hose them off with a strong blast of water, hit the worse spots with insecticidal soap, and let the lady beetles and lacewings mop up the rest.
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
Bite marks and see-through patches all over the leaves
Chewed-up leaves usually come down to two suspects. Japanese beetles are the shiny copper-and-green ones munching away in broad daylight, while slugs and snails sneak in overnight and leave slime trails down by the soil. Pluck the beetles into soapy water first thing in the morning, put out iron-phosphate bait for the slugs, and clear away the damp junk they like to hide under.
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
Stems keeling over or breaking when a storm rolls through
Those tall flower stems really take a hit from wind and heavy rain, and the bigger the clump, the worse it gets. Snip any broken stems back with a clean cut so they can grow again. If the clump sits out in the open, give it stakes or a grow-through support, and if you've got the choice, tuck it somewhere out of the worst 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
New little plants nearby and a clump that keeps getting bigger
Where it's happy, mountain fleece self-seeds and creeps outward slowly on its rhizomes, so you'll spot little newcomers near the parent and watch the clump edge wider each year. Don't panic, though, because it's steady rather than pushy, and it's not invasive. Just deadhead the old spikes before they set seed, pull the seedlings you don't want while they're small, and split a clump once it's outgrown its patch.
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
Got pets or little kids? Good news, because mountain fleece is non-toxic. The ASPCA doesn't list it, and the plant references don't flag any serious toxicity, so you can plant it freely in a garden full of paws and small hands.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Worried about the cat? Don't be. Mountain fleece isn't on the ASPCA toxic list, so if one chews a leaf, the worst you'll see is a bit of passing tummy trouble from the roughage.
Dogs None
Dogs are fine around it. Wolf down a mouthful of leaves and the stomach might get a little loose for an hour, the way any garden green can do, but there's no real poison in it.
Horses Safe
Horses are in the clear, since there's no toxicity on record and they graze it without any trouble. Truth is, they don't much like it, so the tough spikes usually get left alone.
Rabbits Safe
Rabbits can nibble away with no problem. It's actually known for being rabbit-resistant, so they'll usually walk right past it and go for something softer.
Livestock Safe
Cattle, goats, and sheep have nothing to fear from mountain fleece, and there's no record of it ever making farm animals sick.
Birds Safe
Birds are totally fine here. The little seeds and the leaves don't hold anything nasty, so it just sits there as a harmless part of a wildlife border.
People Safe
It's safe to have around the kids, too. It's grown purely for looks, so there's no poisoning worry if a little one picks at it or has a taste.
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 few named picks, and they mostly differ in size and flower color. These two are the ones you'll bump into most.
Firetail
It's a crowd favorite that puts on showy crimson to rose-red bottlebrush spikes from June right through October.
Golden Arrow
It's the compact one, staying at 18 to 24 inches tall and wide, with golden-green leaves that play off 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 easy to make more of, whether you split a clump you've got, let it seed itself, or take a cutting.
DivisionEasy
Spring or fall · One growing season
Want more mountain fleece? Dividing is the easiest and most reliable way to get it. In spring or fall, dig up the rhizomatous clump, break off a few healthy chunks, and pop them back in at the same depth they were. Each one settles in and fills out inside a single growing season.
SeedModerate
Late winter to spring indoors, or self-sown outdoors · One to two growing seasons to reach flowering size
It self-sows all on its own, and you can also gather seed and start it indoors from late winter into spring. Just be patient, because seedlings need one to two growing seasons before they flower. And here's the catch: they might not come true, so a seed-grown plant can wander off 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 off the non-flowering shoots in late spring or early summer. They'll root over several weeks and need a full season to settle in, though honestly most gardeners just grab the spade and divide instead.
Myths
Anything related to knotweed is a garden bully, so mountain fleece is bound to gobble up the border.
Sure, mountain fleece self-seeds and creeps a little where it's happy, but it's flat-out described as not invasive. It's nothing like its bully of a cousin, Japanese knotweed, and a quick deadhead or a division keeps it right where you want it.
It's a poisonous plant, and any family with pets or small children should steer clear of growing it.
Nope. The ASPCA doesn't list it as toxic, and the plant references don't flag any serious toxicity either. It's treated as a fully non-toxic ornamental, so a garden shared with pets and kids is no problem.