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Mercurialis annua

annual mercury

Euphorbiaceae

Mediterranean Europe, North Africa, and western Asia

Deer Resistant

SunFull Sun – Part Shade

WaterMedium

Overview

Mercurialis annua is an erect annual herb of the spurge family, growing 10-50 cm (4-20 in) tall on smooth, branching, four-angled stems. The opposite leaves are oval to lance-shaped, 2-5 cm (0.8-2 in) long, with toothed margins and a slightly fleshy texture, light to mid-green throughout. The species is usually dioecious: male plants carry small green flowers in slender, interrupted axillary spikes, while female plants bear inconspicuous flowers and two-lobed hairy capsules close to the stem. It completes its life cycle in a single season, germinating from spring onward and seeding heavily before frost. The plant colonises cultivated ground, gardens, waste places, and disturbed soil, behaving as a fast weed of fertile, well-drained sites. All parts are toxic, containing irritant compounds that can cause digestive upset in people and livestock if eaten. It tolerates a wide range of soils but grows largest on rich, moist ground in sun or light shade, and dies completely with the first hard frost.

Native Range

Mercurialis annua is native to Europe, North Africa, and western Asia, centred on the Mediterranean region. It has spread widely as a weed of cultivation across temperate North America, Australia, and beyond. It grows on disturbed and cultivated ground from sea level to low hills.

Suggested Uses

Mercurialis annua is not grown as an ornamental and is treated as a weed of gardens and arable land. It has a history of limited use as a traditional dye and folk remedy, both now largely discontinued because of its toxicity. In gardens it is managed rather than cultivated.

How to Identify

Look for a branched annual with opposite, toothed, slightly fleshy leaves on square green stems and separate male and female plants. Male plants show slender axillary spikes of tiny green flowers, while female plants carry small two-lobed bristly capsules near the leaf bases. The absence of milky sap separates it from many other spurges.

Appearance

Size & Dimensions

Height4" - 1'8"

Width/Spread6" - 1'

Colors

Flower Colors

green

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~20 weeks

Spring Summer Fall

Green, petalless flowers appear from late spring through autumn, with overlapping generations across a long season. Male spikes shed pollen to the wind, and female plants set seed within a few weeks. Seeding continues until the first frost ends the plants.

Detailed Descriptions

Foliage Description

light to mid-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

loam clay sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

It grows in full sun to light shade on most fertile, moist, well-drained soils, reaching largest size on rich cultivated ground. As a frost-tender annual it is killed by the first hard freeze and survives winter only as seed. It needs no special care and self-sows freely, often appearing as a volunteer in beds and vegetable plots. Dense stands compete with crops and seedlings for moisture and nutrients. All parts are toxic if eaten. Plants pull up easily before they set seed.

Pruning

As a short-lived annual it is not pruned. Plants are pulled or hoed out before seed sets to limit spread, since each plant produces abundant seed. Removed material remains mildly toxic and is kept out of food and forage.