Alternanthera

How to choose an alternanthera

Little Ruby Alternanthera is the most widely grown: a compact mounding groundcover 30 to 40 centimetres high and up to a metre wide, with deep burgundy leaves. It is widely used in mass plantings as a dark contrast to green and silver foliage. Brazilian Red Hots Alternanthera is a brightly coloured selection from the same species.

Joseph's Coat is the taller form, an upright bushy plant that can reach 60 centimetres to a metre and suits the middle of a bed. For edging, the fine leaved ficoidea types stay low and tight: the Red Threads Alternanthera has very narrow red leaves, and the Tricolor Alternanthera has multi coloured leaves. Joyweed Purple Splash is a further coloured form for mixed plantings.

Where alternanthera works

Alternanthera suits warm temperate, subtropical and tropical climates. It is evergreen and grows nearly all year in frost free coastal Queensland, northern New South Wales, Darwin and Perth. In Sydney and similar mild districts it slows in winter and picks up again as the soil warms. Frost burns the foliage. In areas with light frost the plants are often cut to the ground and reshoot in spring, and in cold districts they are grown as summer bedding or in pots moved under cover.

Sun gives the strongest colour. In part shade the plants grow well but the leaves are greener and the growth looser. They enjoy humidity and summer rain, which makes them more dependable than many foliage plants in the north. See also our groundcover plants, the subtropical plants for warm climates and plants for tropical climates.

Planting and spacing

Plant from spring to early autumn, once the soil is warm and frosts have passed. Alternanthera grows in most soils with reasonable drainage and responds to compost dug in beforehand. Space the mounding groundcover types 50 to 70 centimetres apart for a continuous carpet, Joseph's Coat about 60 centimetres apart, and the fine leaved edging forms 20 to 30 centimetres apart for a solid line. Water in well and mulch between plants until they close over.

Care basics

Water regularly. These are not drought plants, and they wilt and drop leaves when dry, though they recover quickly. Feed in spring and again in midsummer with a slow release fertiliser to keep new coloured growth coming.

Trim to keep plants dense. Tip prune the groundcover types two or three times through the growing season, and clip edging forms as often as needed to hold a line. Older plants become woody and open in the centre. Cut them back by half in spring once the weather warms, never going into winter, and they regrow quickly. After frost damage, leave the burnt growth in place until spring because it protects the crown, then cut back to live shoots. Replace tired plants every few years from tip cuttings, which root in a couple of weeks in warm weather. Small white flowers appear in the cooler months and can be trimmed off.

Common questions

Does alternanthera survive frost?

Frost burns it. In mild areas it often reshoots in spring. In cold districts treat it as a summer plant.

Why is my alternanthera turning green?

Usually too much shade. Move it to more sun or thin whatever is shading it, and the colour returns.

How far apart do I plant Little Ruby?

About 50 to 70 centimetres apart for a carpet that closes over in a season.

Can alternanthera grow in pots?

Yes. It makes a good spiller or filler in a sunny pot with regular water.