Weedbusters

Location: common in northern areas of the North Island, less common in cold regions.

A toxic creeper

Distinctive features:

found in swampy pasture, wetlands, and bush. Forms a 1–1.5m-high clump, with large, leathery, arrow-shaped leaves with a wavy margin. Elegant white, funnel-shaped bracts (a special leaf that looks like a flower) with a central yellow spike make a very pretty sight in late winter and spring. Green or yellow berries follow the flowers.

Warning: all parts of the plant are highly poisonous, and will cause burning to the mouth and throat within a minute of ingestion.

Why is it weedy: long-lived and persists under regenerating canopy, forming dense patches excluding other vegetation. Tolerates wet, wind, salt, hot to cold, most soil types, moderate shade, and is drought-resistant once established. Stock avoid it, allowing it to gradually dominate grazed sites.

How to kill it

Mowing alone doesn’t kill arums. Digging it out doesn’t tend to work as any root or tuber fragments will resprout. Begin clearance at the top of a catchment as seeds spread downstream. Exclude livestock in areas where you are treating plants (as wilted foliage may be more palatable, but is still toxic).

1. Mow tops off at ground level and paint stumps with 1g metsulfuron-methyl + 100ml glyphosate + penetrant per 1L of water. Leave stems and leaves on site to rot down. Dig out tubers, dry and burn, bury deeply, or dispose of at a refuse transfer station.

2. Spray: 3g metsulfuron-methyl 600g/kg + 150ml glyphosate + 10ml penetrant /10L water.

Why this arum is bad news too

One variety of arum – Green Goddess – is particularly widespread because it was a popular cut ‘flower,’ now banned from sale and propagation. The large, greenishwhite ‘flowers’ are followed by round green or yellow berries (1 cm) which grow on the flower stalk after the leaves die back.