Pasture Weed Watch Redroot

IT NEVER ceases to amaze me how much work there is to do on my lifestyle block, especially in spring.

I love this time of year. Everything starts to wake up as the soil warms up and the plants and animals are kissed by the spring sunshine. The biggest problem is the weeds always seem to grow twice as fast.

One troublemaker I have to deal with on my block is redroot ( Amaranthus

powellii), sometimes called Prince of Wales feather, or pigweed.

This annual weed starts to emerge in late spring. It grows aggressively throughout summer until the first frosts kill it, or if I get there first with my sprayer.

Generally, it's not a big issue in perennial pasture. But once you cultivate for cropping or put in new grass, the plants seem to come from nowhere.

Redroot is an upright plant, up to 1m tall. Its green foliage has a red tinge and it's easily spotted once it's above pasture-height. The leaves are spadeshaped; when small, you might confuse it with weeds like black nightshade or galinsoga.

But it's clear once the seed head emerges. It has a large, elongated greenbrown, spiky seed head which produces large numbers of black, shiny seeds.

How to control it

Control is fairly easy: mow it. All this upright annual wants to do is grow a seed head, drop its seeds, then die. If you mow it before it reaches seed head stage, it usually kills it.

I use a combination spray of MCPA/ MCPB, sold as Tropotox Ultra or Thistrol Plus. Flumetsulam is also effective. Both these options are safe for use on pasture that includes clover.

Why is it a weed? Out-competes crops and new pasture Where is it found? Across New Zealand Is it toxic? Contains high levels of oxalates, and can cause nitrate poisoning in livestock