Ornamental · Polygonaceae
Mountain Fleece
Persicaria amplexicaulis
Set it where the ground stays damp with room to spread, and mountain fleece lifts 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 the kind of perennial that carries a border through the long middle of the season. From June into October it holds slim red bottlebrush spikes above tidy green clumps, giving a bed reliable color long after the early flush has faded. A member of the knotweed family with far better manners than the name suggests, it settles into a clump that widens slowly and keeps its place in a scheme.
It belongs in the cooler, damper corner of a garden, the low ground beside a pond or the moist edge of a mixed border where drier plants sulk. Full sun suits it wherever the soil stays moist, and it takes part shade with grace. Hardy to zone 4, it retires each winter and returns each spring, standing waist-high at 3 to 4 feet across, an easy scale to place among mid-border companions.
The upkeep is the sort that folds neatly into a season's rhythm. Cut last year's stems to the ground in late winter, refresh a tired clump every few years, and glance now and then for aphids and slugs. Deer and rabbits leave it be, so it stays a calm, dependable anchor in a border or a poolside planting that mostly looks after itself.
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 settle into the scheme.
Light
Mountain fleece is at its best in full sun, though it takes partial shade or partial sun in good style. The single condition is moisture, since in full sun the soil must stay damp or the planting loses its poise in high summer.
Water
This is a plant with a real thirst. Keep the soil consistently moist, watering about every 3 to 7 days, and more often through hot spells or strong sun. It even makes a graceful edge to a pond, at ease in ground too wet for most border plants.
Soil
Give it average, medium to wet but well-drained clay or loam. It thrives in steadily damp ground that would defeat fussier plants, and it is untroubled by pH, growing happily across a wide band from 6.0 to 8.0.
Temperature
Mountain fleece is strikingly cold-hardy, down to -29°F (-34°C), and comfortable up to about 86°F (30°C). It retires in winter and rises again in spring, so a hard freeze holds no threat for an established clump in the border.
Humidity
Outdoor air brings whatever humidity the season offers, and the plant is unbothered by it. What it asks for is moisture at the root, not in the air around its stems.
Feeding
Feed with a light hand. Work a balanced general-purpose fertilizer or a little compost into the soil at the start of the growing season in spring, and that is usually enough. Restraint pays, since too much nitrogen brings the soft growth aphids favor.
Pruning
Cut the whole plant back to the ground in late winter or early spring to clear the stage for fresh shoots. Through summer, snip away the spent spikes to draw out more bloom and keep self-seeding in check.
Repotting
Mountain fleece is a border plant, not a container subject, but it does want dividing every 3 to 4 years. Lift and split the clump when it loses vigor, hollows in the center, or offers fewer and smaller flower spikes.
Size & spacing
Allow 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 fills its place in the scheme without crowding its neighbors.
When to plant
Mountain fleece keeps a graceful seasonal calendar. Start seed indoors in late winter, place young plants out in spring once frost has passed or again in early fall, and the flower spikes carry the display 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 troubles a border, so most of what turns up is a grazed leaf or a stem laid low by a storm. Match what you see below and step in early, while the remedy is still a light touch.
Fresh growth puckering beneath a scatter of small pests
When the fresh shoots start to curl, look closer and you will usually find aphids, the pest that visits mountain fleece most. They settle on the soft new growth and leaf undersides, draw sap, and leave a sticky glaze in their wake. A firm rinse with the hose sends most of them off, insecticidal soap tidies the heavier patches, and the garden's own lady beetles and lacewings quietly handle 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
Foliage marred by torn openings and lace-like feeding
Ragged foliage points to a pair of familiar diners. The metallic copper-and-green Japanese beetles work the border in daylight, while slugs and snails slip in after dusk and leave a glistening trail near the soil. Lift the beetles into soapy water each morning, lay out iron-phosphate bait for the slugs, and clear the damp litter that gives them cover.
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
Upright stems laid low in the wake of wind and rain
The elegant height that makes mountain fleece such a border presence is also its vulnerability, and wind and heavy rain can leave a big clump splayed. Trim the broken stems back with a clean cut and fresh growth follows. A discreet ring of grow-through supports steadies an exposed stand, and a planting position tucked out of the prevailing wind spares it the worst weather.
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
Uninvited seedlings and a planting that slowly claims more ground
Given a spot it likes, mountain fleece self-seeds and drifts outward slowly on its rhizomes, so a few volunteers appear beside the parent and the clump gently broadens across the border over the years. The movement is leisurely, never a takeover, and the plant is not invasive. Deadhead the spent spikes before seed forms, ease out the seedlings you would rather not keep, and divide a clump once it has outgrown its place in the design.
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
For a garden shared with pets or children, the note is a happy one: mountain fleece is non-toxic. The ASPCA does not list it, and horticultural references report no serious toxicity, so it can take its place freely in a bed that welcomes plenty of paws and small hands.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat wandering the border is in no danger, since mountain fleece never made the ASPCA toxic list, and a nibbled leaf offers nothing worse than a passing touch of stomach upset from the roughage.
Dogs None
The family dog can share the garden freely. A snatched mouthful of foliage might loosen the stomach for an hour, as any garden greenery can, yet it carries no true poison.
Horses Safe
Horses come to no harm from it, with no toxicity on record and grazing well tolerated. The coarse spikes hold little appeal, so most simply pass them by.
Rabbits Safe
Rabbits can browse the planting without concern. Its reputation for rabbit resistance means they usually drift toward softer neighbors instead.
Livestock Safe
Cattle, goats, and sheep face no known hazard from mountain fleece, and no case of it poisoning farm animals has been recorded.
Birds Safe
Birds are entirely safe among it. The small seeds and foliage carry nothing harmful, so it sits as a benign feature of a wildlife border.
People Safe
Children can play beside it in comfort. It is grown purely for its looks and presents no poisoning risk should a curious child handle or taste 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 is offered in a small, well-chosen set of named selections that differ mainly in scale and flower color. These two turn up most often in the border.
Firetail
A perennial favorite for the border, lifting showy crimson to rose-red bottlebrush spikes from June straight into October.
Golden Arrow
A compact choice for tighter plantings, holding to 18 to 24 inches tall and wide, with golden-green foliage set beneath 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 for a larger planting, whether you split an existing clump, let it self-sow, or take a cutting.
DivisionEasy
Spring or fall · One growing season
Division is the surest way to build a sweep of mountain fleece across a border. In spring or fall, lift the rhizomatous clump, part it into healthy pieces, and reset them at their original depth. Each piece settles and fills its space within a single growing season.
SeedModerate
Late winter to spring indoors, or self-sown outdoors · One to two growing seasons to reach flowering size
It sows itself with ease, and collected seed can be started indoors from late winter into spring. The reward asks for patience, since seedlings take one to two growing seasons to reach flowering size. Bear in mind that seed rarely comes true, so the offspring may drift from a named cultivar.
Stem cuttingsModerate
Late spring to early summer · Several weeks to root, one season to establish
Softwood basal cuttings taken from non-flowering shoots in late spring or early summer are another option. They root over several weeks and need a full season to settle, though most gardeners turn to division for the border.
Myths
A knotweed cousin can only spell trouble, and given time mountain fleece will annex the whole garden.
Mountain fleece does self-seed and edge outward slowly where it settles, yet it is plainly described as not invasive. It behaves nothing like its aggressive cousin Japanese knotweed, and a season's deadheading or a simple division keeps it within the lines of a planned bed.
This perennial hides harmful compounds and has no place where children or pets wander.
The ASPCA does not list it as toxic, and horticultural references note no serious toxicity concerns. It is treated as a fully non-toxic ornamental, at home in a garden shared with pets and children.