Gooseneck loosestrife

Sun

Full sun to partial shade; provide afternoon shade in hot summers.

Water

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

Soil

Humus-rich, moisture-retentive soil with reasonable drainage; tolerates clay and a broad range of soil pH.

Height

2-3 ft (0.6-0.9 m)

Spread

2-3 ft (0.6-0.9 m) initially; runners can form much wider colonies.

Flowers

Mid- to late summer; small white flowers packed into arching, pointed spikes.

Foliage

Upright leafy stems with pointed, mid-green leaves, often turning orange or red in autumn; dies back for winter.

Growth

Fast once established, especially in moist, fertile soil.

Care needed

High

• Pollinators
• Cold hardy
• Low allergen

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

Difficulty

Moderate

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

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Water deeply during dry weather rather than allowing the root zone to dry out repeatedly.
• Apply a thin layer of compost in spring; avoid heavy feeding, which encourages excessive growth.
• Mulch to conserve moisture, keeping mulch clear of emerging shoots.
• Check the edge of the planting several times during the growing season and dig out escaping rhizomes.
• Divide congested clumps in spring, keeping only the amount you have room to grow.
• For tight spaces, use a large container and check drainage holes regularly for escaping roots.

Pruning. Cut dead stems to ground level in late autumn or late winter, before new shoots emerge. Remove spent flower spikes if you want a tidier appearance, but deadheading will not control underground spread.

Late winter

Cut down remaining dead stems before new growth starts.

Spring

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

Late spring

Inspect surrounding soil for runners and lift unwanted shoots with their attached rhizomes.

Summer

Water during dry spells and check that neighbouring plants are not being crowded out.

Late summer

Remove faded flower spikes if desired and make another check for spreading rhizomes.

Autumn

Enjoy the foliage colour, then remove collapsed growth or leave sound stems until late winter.

• Use as a broad summer drift in a large, moist border where its spread can be monitored.
• Pair with robust ornamental grasses for a contrast between curved white flower spikes and fine-textured foliage.
• Plant in a contained white-flowered border with astilbes and hostas.
• Use beside a garden pond above the permanently waterlogged margin, away from natural waterways.

Garden styles it suits: Cottage garden, English country, White garden, Blues and silvers, New perennial (prairie) and Japanese.

Plant it with: Astilbe, Hosta, Siberian iris, Joe-Pye weed, Switchgrass and Meadowsweet.

Wildlife: Flowers attract bees and other pollinating insects. Dense colonies can displace other garden plants; this Asian species is not a substitute for locally native wetland vegetation.

• Unwanted spread: dig out runners with all attached rhizome sections; repeat checks throughout the growing season.
• Wilting or brown leaf edges in dry weather: water deeply and mulch; provide afternoon shade in hotter gardens.
• Slugs and snails on young shoots: inspect at dusk, remove by hand, and use labelled iron-phosphate bait if needed.
• Rust or leaf spotting: remove badly affected foliage, avoid wetting leaves when watering, and improve airflow.

Not known to be toxic to cats, dogs, horses or people. Species-specific safety information is limited, so do not treat the leaves, flowers or roots as edible or allow pets to eat substantial quantities.

Where it spreads. Spreads aggressively by rhizomes in moist gardens, including those in the northeastern and midwestern United States, southern Canada, the United Kingdom and temperate Australia. It can escape cultivation and is naturalized in parts of the eastern United States. These are not all regions where it is officially listed as invasive; check local guidance and keep it out of natural areas.

• Willow-leaved loosestrife (Lysimachia ephemerum)

  Has narrow, grey-green leaves and slender, largely upright white flower spikes rather than the strongly bent, goose-necked spikes.

• Purple loosestrife (Lythrum salicaria)

  Usually has upright purple-pink flower spikes and opposite or whorled leaves, unlike the curved white spikes and alternate leaves of gooseneck loosestrife. It belongs to a different plant family.

Gooseneck refers to the bent flower spikes, while clethroides means resembling Clethra, another plant with spikes of small white flowers.

Propagation. Divide in spring, separating rooted shoots with attached rhizomes and replanting promptly. Do not dump unwanted roots or soil containing rhizome fragments in natural areas.

Accepted botanical name

Lysimachia clethroides

In the US and Canada

Introduced in Canada and the lower 48 states.

Native range

China South-Central, China Southeast, Hainan, Japan, Korea, Laos, Manchuria, Primorye, Taiwan and Vietnam.

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