Caltha spp.

marsh marigold

Ranunculaceae Both hemispheres, cool temperate

Attracts Pollinators Deer Resistant Container Friendly

Native to North America

SunFull Sun – Part Shade

WaterHigh

HardinessZones 3–7

Overview

Caltha spp. is a genus of perennial marsh and bog plants in the buttercup family (Ranunculaceae), found in cool, wet places across both the northern and southern hemispheres. The widely grown C. palustris, marsh marigold or kingcup, forms clumps 8-24 inches (20-60 cm) tall and wide of glossy, rounded to kidney-shaped dark green leaves on hollow stems. In spring the plants carry cup-shaped flowers 1-2 inches (2.5-5 cm) across, made of five to nine golden-yellow petal-like sepals around a centre of many stamens; white-flowered species grow in the southern hemisphere. Flowers are followed by clusters of small podlike follicles that split to release seed onto wet ground or water. The whole plant contains protoanemonin and other irritant compounds, so the raw sap can blister skin and the foliage is toxic if eaten. Caltha spp. grows in marshes, wet meadows, ditches, pond edges, and slow streams, and it goes dormant or scorches where the soil dries out in summer.

Native Range

Caltha spp. has a wide distribution in cool temperate, boreal, and montane regions of both hemispheres. C. palustris is native across the northern hemisphere in Europe, Asia, and North America, while other species occur in southern South America, New Zealand, and Australia. Plants grow in marshes, wet meadows, fens, stream banks, and seasonally flooded ground.

Suggested Uses

Caltha palustris is used at the margins of ponds, streams, and bog gardens and in wet wildflower meadows for early-season yellow flowers. It suits permanently moist ground in USDA zones 3-7 alongside other marginal plants. Its irritant, toxic sap limits its use where children or pets handle plants at the water edge.

How to Identify

Look for clumps of glossy, rounded to kidney-shaped dark green leaves on hollow stalks in wet ground, topped in spring by cup-shaped flowers of five to nine waxy yellow sepals (white in some southern species). The flowers lack true petals, and the centre holds many yellow stamens. The wetland habit, glossy heart-shaped leaves, and waxy yellow cups separate it from true buttercups, which have smaller, flatter flowers and divided leaves.

Appearance

Size & Dimensions

Height8" - 2'

Width/Spread1' - 2'

Colors

Flower Colors

yellow

white

Foliage Colors

green

Bloom Information

Bloom Period

~5 weeks

Spring

Flowering occurs in early to mid spring, often March to May in the northern hemisphere, among the first wetland plants to bloom. Each clump flowers for three to five weeks, sometimes with a lighter second flush in autumn in mild, wet conditions. Cool, damp springs lengthen the display.

Detailed Descriptions

Flower Description

Golden-yellow, white in some species

Foliage Description

Glossy dark green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-8 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

loam clay peat

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

2-3 years to mature clump

Care & Maintenance

Care Guide

Plants grow in full sun to part shade in permanently moist to wet soil at pond and stream margins or in bog gardens, and they tolerate standing water a few inches deep. They are hardy to about USDA zone 3 but suffer where the soil dries in summer, when the foliage browns and the plant goes dormant early. Clumps can be lifted and divided after flowering. Rich, boggy soil suits them, and they need no feeding in fertile ground. Powdery mildew can mark the leaves in stagnant air late in the season.

Pruning

Faded flower stems and tired leaves can be removed after flowering to tidy the clump. No structural pruning is needed. Plants that brown in summer drought can be cut back, and fresh leaves return with autumn rains or cooler weather.