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Rorippa palustris

bog yellowcress

Brassicaceae

Northern Hemisphere (Europe, Asia, North America)

Attracts Pollinators

Native to North America

SunFull Sun – Part Shade

WaterHigh

Overview

Rorippa palustris is a hairless annual or short-lived perennial of the cabbage family, growing 6-24 inches (15-60 cm) tall with an erect, branched stem. The lower leaves are deeply pinnately lobed and lyre-shaped, up to 6 inches (15 cm) long, while the upper leaves are smaller and clasp the stem with ear-like bases. Many small yellow flowers, each about 0.08-0.12 inch (2-3 mm) across with four petals, open in elongating clusters from June to October. The flowers give way to short, plump, slightly curved pods 0.2-0.4 inch (5-10 mm) long that are shorter than those of most related cresses. The plant grows quickly in wet ground and can flower within a few months of germinating. It is variable in size and form depending on water and nutrients, staying a few inches tall on dry mud and reaching full height in rich, wet soil. Plants die after seeding in their first or second year.

Native Range

Found through much of the Northern Hemisphere, including Europe, Asia, and North America, and naturalised more widely. Grows on bare wet mud at pond and lake margins, in ditches, marshy fields, and damp disturbed ground, mainly in the lowlands.

Suggested Uses

Occurs in wetland and pond-margin restoration and in damp wildlife areas rather than ornamental plantings. It colonises exposed mud from the natural seed bank where water levels fluctuate. Its weedy seeding and need for wet, bare ground limit any deliberate garden use.

How to Identify

Identified by the lyre-shaped, deeply lobed lower leaves, the clasping upper leaves with ear-like bases, and the small four-petalled yellow flowers about 0.08-0.12 inch (2-3 mm) across. The short, plump, slightly curved seed pods are diagnostic, being far shorter than the long pods of watercress and most Rorippa spp. relatives. The hairless foliage and wet, muddy habitat are further pointers.

Appearance

Size & Dimensions

Height6" - 2'

Width/Spread4" - 1'

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~16 weeks

Summer Fall

Flowers over a long season from June to October, with new flowers and ripening pods present at the same time. Individual plants flower for several weeks once mature. The extended period reflects staggered germination on exposed mud through the summer. Flowering ends with the first hard frosts.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-12 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

silt clay loam

Drainagewet

Water & Climate

Water Needs

High

Care & Maintenance

Care Guide

Grows in full sun on wet, muddy, nutrient-rich soils at the water edge and tolerates seasonal flooding. As a fast annual it depends on bare, damp ground for seedlings to establish and dies once seed is set. It does not persist under dense vegetation or in dry soil. Plants self-seed heavily, leaving a long-lived seed bank in pond mud that germinates when water levels drop. It is treated as a weed in wet arable fields and on reservoir margins.

Pruning

No pruning is needed. Removing flowering stems before the pods ripen reduces seeding into surrounding mud. The plant dies after seeding and is cleared with other annual growth at the end of the season.