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Lythrum spp.

lythrum loosestrifes

Lythraceae

Temperate and subtropical wetlands of Eurasia, Africa, Australia, and the Americas

Attracts Pollinators Attracts Butterflies

Native to North America

SunFull Sun – Part Shade

WaterHigh

HardinessZones 3–10

Overview

Lythrum spp. is a genus of about 35 species in the family Lythraceae, made up of herbaceous perennials and a few annuals found across temperate and subtropical wetlands worldwide. Plants form erect, often four-angled stems 0.7-6.5 ft (20-200 cm) tall, carrying narrow lance-shaped to linear leaves 0.4-4 in (1-10 cm) long in opposite pairs or whorls. Flowers open along slender terminal spikes in shades of purple, magenta, and rose-pink, occasionally pale lilac, each bloom 0.3-0.8 in (8-20 mm) across with 4-6 crinkled petals. Many species are tristylous, producing three floral forms with differing style and stamen lengths that promote cross-pollination. The genus spans wet meadows, marsh edges, ditches, and riverbanks, with L. salicaria reaching 5-6.5 ft (1.5-2 m) in fertile sites and smaller annuals such as L. hyssopifolia staying under 24 in (60 cm). L. salicaria is regulated as a noxious weed across many US states and Canadian provinces, where it forms dense stands that displace native wetland vegetation. Foliage dies back to the ground each winter in temperate climates and regrows from a woody crown. Flowering extends through summer, and the blooms are visited by bees and butterflies for nectar. Cold tolerance varies by species, spanning roughly USDA zones 3 through 10.

Native Range

The genus is distributed across Europe, Asia, Africa, Australia, and the Americas, with the greatest concentration of species in the temperate Old World. L. salicaria is native to Eurasia and is naturalized widely in North America.

Suggested Uses

Non-invasive Lythrum spp. species and sterile cultivars are planted at pond and stream margins, in rain gardens, and in moist borders. The summer flower spikes are used in cut arrangements. Planting of L. salicaria and its cultivars is prohibited in many regions because of its invasive spread.

How to Identify

Identify Lythrum spp. by erect four-angled stems bearing opposite or whorled lance-shaped leaves with smooth margins. Slender terminal spikes carry whorls of 4-6 petaled flowers in purple to magenta, each 0.3-0.8 in (8-20 mm) wide. The crinkled petals and protruding stamens of differing lengths separate the genus from similar wetland plants.

Appearance

Size & Dimensions

Height8" - 6'7"

Width/Spread1' - 3'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~10 weeks

Summer Fall

Flowering occurs through summer into early autumn, typically June to September in temperate regions. Each spike opens from the base upward over several weeks. In warm climates some species bloom across an extended period.

Detailed Descriptions

Flower Description

purple to magenta

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

clay loam silt

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

1-2 years

Care & Maintenance

Care Guide

Most Lythrum spp. species grow in full sun to light shade in consistently moist to wet soil, including pond margins and bog gardens. They tolerate a soil pH from about 5.5 to 7.5 and adapt to clay, loam, and silty ground that holds water. Established plants withstand seasonal flooding and standing water at the roots. Cold tolerance varies across the genus, spanning roughly USDA zones 3 to 10. L. salicaria spreads quickly by seed and rhizome and is restricted from sale and planting in many jurisdictions. Where permitted, clumps can be divided in spring to keep them vigorous.

Pruning

Spent stems are cut to ground level in late autumn or early spring after the foliage dies back. Removing flower spikes before seed matures limits self-seeding, a particular concern with the invasive L. salicaria. No other routine pruning is required.