Calla spp.

bog arum

Araceae Circumboreal northern hemisphere

Attracts Pollinators Container Friendly

Native to North America

SunFull Sun – Part Shade

WaterHigh

HardinessZones 3–8

Overview

Calla spp. is a genus in the arum family (Araceae) represented by a single species, Calla palustris, a rhizomatous marginal-aquatic perennial of the cool northern hemisphere. The creeping rhizome runs along wet ground or just below shallow water, rooting at the nodes and producing glossy, broadly heart-shaped leaves 2-4 inches (5-10 cm) long on stalks 4-8 inches (10-20 cm) tall. From late spring the plant bears a flat white spathe about 1.5-2.5 inches (4-6 cm) long that surrounds a short greenish-yellow spadix carrying the true flowers. Pollinated chiefly by water snails and small flies, the spadix ripens into a tight cluster of red berries by late summer. The whole plant contains calcium oxalate crystals, which make the raw foliage and berries toxic to people and pets if eaten. Calla spp. grows along acidic bogs, pond margins, and slow stream edges and spreads into floating mats, which can crowd small water features. The florist calla lily belongs to the unrelated genus Zantedeschia spp. rather than to Calla spp..

Native Range

Calla palustris has a circumboreal distribution across the cool temperate and subarctic northern hemisphere, including northern North America, Europe, and northern Asia. It grows in still and slow-moving fresh water such as bogs, fens, pond edges, and ditch margins, usually in acidic, peaty conditions.

Suggested Uses

Calla palustris is used at the margins of wildlife ponds, in bog gardens, and in container water gardens kept permanently wet. It suits naturalistic plantings in acidic, boggy ground in USDA zones 3-8. Its toxic berries and foliage limit its use where children or pets reach the water edge.

How to Identify

Look for glossy, broadly heart-shaped leaves on a green rhizome creeping over wet mud or shallow water. A single flat white spathe, open rather than funnel-shaped, sits behind a short greenish spadix. By late summer the spadix becomes a clustered head of red berries. The aquatic habit and open white spathe separate it from Zantedeschia spp., whose spathe is rolled into a trumpet.

Appearance

Size & Dimensions

Height4" - 10"

Width/Spread1' - 2'

Colors

Flower Colors

white

green

Foliage Colors

green

Bloom Information

Bloom Period

~6 weeks

Spring Summer

The white spathes appear from late spring into midsummer, roughly May to July. Each spathe lasts one to two weeks, and a colony opens its spathes over several weeks. Red berries follow and ripen from August.

Detailed Descriptions

Flower Description

White spathe with greenish-yellow spadix

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 Range4.5 - 6.5(Acidic)

357912

Soil Types

peat loam

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

2-3 years to form a colony

Care & Maintenance

Care Guide

Plants grow in full sun to part shade at the margins of ponds or in consistently wet, acidic, peaty soil. They need permanently moist ground or water 0-4 inches (0-10 cm) deep over the rhizome and tolerate winter cold to about USDA zone 3. Growth spreads by rhizome rather than needing replanting, and crowded mats can be thinned by lifting sections in spring. The plant fails in dry or alkaline soil. Few pests trouble it, though aphids may gather on the flower stalks.

Pruning

No formal pruning is needed. Faded spathes and yellowing leaves can be removed at the rhizome, and spreading colonies can be reduced by lifting and dividing rhizome sections in spring. Berry heads can be taken off before they drop if self-seeding is unwanted.