Megathyrsus spp.

guinea grass

SunFull Sun – Part Shade

HardinessZones 9–12

Overview

Megathyrsus spp. is a small genus of tall tropical grasses in the family Poaceae, most familiar as M. maximus, Guinea grass, a robust tussock grass native to Africa. Plants form dense clumps of arching leaf blades and flowering stems that reach 3–10 ft (0.9–3 m) tall, occasionally taller in rich soil. The leaf blades are broad, flat, and rough-edged, to about 1.4 in (35 mm) wide, rising from a knotty base. Airy, branching panicles up to 18 in (45 cm) long carry many small spikelets that ripen to straw and shed abundant seed. As a fast-growing C4 grass, it grows vigorously in warmth and responds strongly to nitrogen, which has made it a major pasture and forage grass across the tropics. The same vigor makes it a serious invasive weed in many regions, including parts of Australia, the Americas, and the Pacific, where it crowds out native plants and carries intense fires. It tolerates a wide range of soils, drought once established, and partial shade. Frost cuts back the top growth, and hard freezes kill it. Tussocks regrow rapidly from the crown after cutting, grazing, or burning.

Native Range

Megathyrsus maximus is native to tropical and subtropical Africa, including the Arabian Peninsula. It has been introduced across the warm regions of the world as a forage grass and is now naturalized widely.

Suggested Uses

Grown chiefly as a tropical pasture and cut-and-carry forage grass for cattle and other livestock. It is also used for erosion control and as a tall screen or clump grass in large warm-climate gardens. Outside managed use it is widely regarded as an environmental weed.

How to Identify

Recognized by tall, dense tussocks of broad, flat, rough-edged leaf blades and stems to 10 ft (3 m), rising from a knotty, sometimes hairy base. Loose, much-branched panicles up to 18 in (45 cm) long carry many small spikelets that ripen to straw colour. The large size, open seed heads, and clumping habit separate it from most pasture grasses.

Appearance

Size & Dimensions

Height3' - 10'

Width/Spread2' - 5'

Colors

Flower Colors

green

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~16 weeks

Summer Fall

Flowering and seeding run mainly through the warm, wet season and can continue much of the year in the tropics. The airy panicles release large quantities of light, wind- and animal-dispersed seed. Plants flower within months of germinating, which speeds their spread.

Detailed Descriptions

Flower Description

green to straw

Foliage Description

green to blue-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 Range5.0 - 7.5(Neutral)

357912

Soil Types

sand loam clay

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

tender

Time to Maturity

1 year

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Megathyrsus maximus grows in full sun to light shade on a wide range of soils, from sands to clays, and tolerates drought once the deep root system is established. It responds strongly to moisture and nitrogen, putting on bulk quickly in warm, wet conditions. As forage it is cut or grazed on rotation, regrowing fast from the crown. Frost knocks back the foliage and hard freezes kill the plant, confining it to frost-free and near-frost-free climates. Because it self-seeds heavily and spreads into bushland, it is treated as a weed outside pasture and is removed before seed set in sensitive areas. Burning and slashing both trigger vigorous regrowth from the tussock base.

Pruning

In pasture the grass is cut or grazed on rotation to keep it leafy and productive. Clumps are slashed or mown low before seed set to limit spread into surrounding land. Cutting and burning both prompt fast regrowth from the crown.