Yellow loosestrife

Sun

Full sun to partial shade; some afternoon shade helps in hot summers.

Water

Keep the soil evenly moist, especially during establishment and flowering. Established plants tolerate brief dry spells, but prolonged drought causes wilting and scorched foliage.

Soil

Moist, humus-rich soil that drains reasonably well; tolerates clay and a broad range of soil pH. Avoid permanently submerged planting sites.

Height

2-3 ft (0.6-0.9 m)

Spread

1-2 ft (0.3-0.6 m) initially; spreading colonies can become much wider.

Flowers

Early to midsummer, sometimes continuing into late summer; golden-yellow, cup-shaped flowers clustered around the upper stems.

Foliage

Pointed, oval green leaves arranged in opposite pairs or whorls along upright stems; dies back in winter.

Growth

Fast once established, spreading by underground rhizomes.

Care needed

Medium

• Pollinators
• Cold hardy
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.7 ft (0.53 m)

3. After 2 years

   2.5 ft (0.75 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Invasive in

the US and Canada

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Water deeply during dry weather rather than allowing repeated wilting.
• Apply a thin layer of compost in spring; rich soil rarely needs additional fertiliser.
• Mulch to conserve moisture, keeping mulch clear of emerging shoots.
• Dig out wandering rhizomes each spring, removing the underground stems rather than just pulling off shoots.
• Divide congested clumps in spring or autumn, keeping only the amount you want to grow.

Pruning. Remove faded flowering stems if you want a tidier appearance and less seed production; this will not stop rhizome spread. Cut dead stems to ground level in late autumn or late winter before new shoots emerge.

Late winter

Cut down any remaining dead stems before fresh growth begins.

Spring

Plant or divide clumps, water thoroughly, and add a thin compost mulch.

Late spring

Check the edge of the clump and dig out rhizomes growing into neighbouring plants.

Summer

Water during dry spells and remove faded flower stems if desired.

Early autumn

Divide or reduce established colonies while the soil is still warm and moist.

• Use in a generous cottage border with other robust perennials for a strong block of summer yellow.
• Combine with purple-flowered cranesbills or Siberian irises for colour contrast in moist soil.
• Plant along a managed woodland edge where there is enough light for good flowering.
• Use in a contained bed beside a pond, above the permanently waterlogged margin and away from natural waterways.

Garden styles it suits: Cottage garden, English country, Traditional, Woodland, Farmhouse and Romantic rose garden.

Plant it with: Siberian iris, Hardy cranesbill, Daylily, Meadowsweet, Purple coneflower and Joe-Pye weed.

Wildlife: Flowers attract bees, including specialist oil-collecting bees where these occur. It is not a native substitute for local wetland plants, and spreading colonies can displace other vegetation.

• Unwanted spread: dig out creeping rhizomes regularly; do not put viable roots into cool home compost or dump them outside the garden.
• Slugs and snails on young shoots: inspect emerging growth and use hand-picking or wildlife-conscious slug controls where needed.
• Rust or leaf spots: remove badly affected leaves, clear infected debris, and improve air circulation.
• Wilting and brown leaf edges in dry soil: water deeply, mulch, and provide afternoon shade in hotter gardens.

Not generally known to be toxic to people, cats, dogs or horses, but reliable species-specific information on ingestion is limited. No particular poisonous part is established; do not treat the leaves, flowers or roots as edible.

Where it spreads. Spreads aggressively by rhizomes in gardens in the UK, temperate parts of the United States and southern Canada, and cool-temperate Australia. It has escaped cultivation in parts of North America, including the Pacific Northwest and northeastern United States. Keep it out of natural areas and check local invasive-plant guidance before planting.

• Garden loosestrife (Lysimachia vulgaris)

  Usually has branched clusters of yellow flowers toward the tops of the stems rather than the conspicuous tiers of flowers nestled among upper leaves found in yellow loosestrife.

• Fringed loosestrife (Lysimachia ciliata)

  Has conspicuously hairy leaf stalks and more loosely arranged, often nodding yellow flowers on slender stalks.

• Purple loosestrife (Lythrum salicaria)

  Bears tall spikes of purple-pink flowers, not yellow cups; it belongs to a different plant family and is a serious invasive wetland plant in much of North America.

The species name punctata means 'dotted' or 'spotted', referring to the small glandular dots on the plant.

Propagation. Divide in spring or early autumn, giving each piece healthy roots and several shoots. Rhizome fragments can regrow, so collect unwanted pieces carefully; propagate named cultivars by division to preserve their foliage characteristics.

Accepted botanical name

Lysimachia punctata

In the US and Canada

Introduced in Canada and the lower 48 states.

Native range

Albania, Austria, Bulgaria, Czechoslovakia, Greece, Hungary, Iran, Italy, Krym, North Caucasus, Poland and Romania.

Measured

Soil pH 5.5 to 6.5. Average height 49 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.