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Caltha palustris

Caltha palustris

The marsh marigold, Caltha palustris,  is one of the few native perennials that have been awarded an AGM. It is an essential plant to brighten up the margins of a pond or a boggy area with sunny yellow flowers (hence its other common name of kingcup).  It flowers along the Stream, by the Lake and in the Upper Bog Garden before almost anything else.

Vital statistics

Common name
Kingcup, marsh marigold, cow lily
Family
Ranunculaceae
Height & spread
30 - 60cm (12 - 24in) x 40 - 60cm (16 - 24in).
Form
Herbaceous perennial
Soil
Rich, boggy soil at the water's edge
Aspect
Full sun
Hardiness
Fully hardy

Caltha

This genus contains approximately 12 species of deciduous perennial, marginal water plants, bog plants and rock garden plants that we grow for their attractive flowers, which are similar to buttercups.

They are widespread in temperature regions of both hemispheres.
The leaves are kidney to heart-shaped, fleshy, and bright to dark green with sturdy stalks.

The flowers range in colour from white through pale yellow to gold and have five tepals (more in the double-flowered cultivars). They flower from February to April and sometimes have a second flush in late summer. Caltha are one of the earliest perennials to flower.

The plant was once used medicinally and named verrucaria because of its supposed ability to cure warts. It is now considered too toxic for such use.

Caltha palustris

You can find this species growing in shallow water or bogs, hence its name palustris meaning marsh-loving. Plants nearest water flower earlier, probably due to the fact that their roots experience less frozen soil.

In spring, bright golden-yellow, waxy flowers, 4cm (1.5in) across and very similar in appearance to buttercups, are borne on upright stems, 30 - 45cm (12 - 18in) tall.

'Flore Pleno' has double yellow flowers with greeny yellow centres and a height and spread of 25cm (10in). Caltha palustris var. alba is compact, clump-forming and has single white flowers.

Cultivation

  • Caltha palustris is a marginal or marshland plant which thrives with its feet wet, but likes them to be well anchored. Having some at the water's edge and some further away is desirable as it spreads the season of flower.
  • Prone to powdery mildew.

Propagation

  • Propagate by division at the end of the summer or very early in spring so as not to spoil the season's display.
  • Sow seed as soon as it is ripe and keep damp.

AGM

The RHS Herbaceous Plant Committee awarded Caltha palustris an Award of Garden Merit and described it as:

'Rhizomatous herbaceous perennial to 60cm, with rounded, rich green leaves and clusters of deep yellow flowers 4cm wide.'

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