Wireweed

Polygonum aviculare

Wireweed (Polygonum aviculare) is a widespread annual with wiry, trailing stems that form mats up to 1 m in width. Wireweed (or wire weed) prefers to germinate in wet soils so it is problematic in winter and in spring sown crops as it can be very competitive and smother crops. Once larger than a seedling, is difficult to control, with selective herbicides in crops.

Cotyledons:

Long
Apex rounded
Base not tapered
Stalkless

Leaves:

Thin spear-shaped
Rigid

Related Pests

White Clover

Trifolium repens

A low growing perennial, white clover (Trifolium repens) has spreading stems that root at the nodes. The leaves consist of three leaflets (in a shamrock shape) which are hairless, finely toothed, often with a white heart shaped markings. The flowers are white with a pink tinge, and grouped in round heads 1.5-3cm in diameter. Widely distributed and very common in New Zealand, white clover is found in pasture, lawns, cultivated and waste land. It plays a big part in the honey bee industry with clover honey being the most common honey type in New Zealand.

Wild Turnip

Brassica rapa subsp. sylvestris

A member of the Brassicaceae family, wild turnip (Brassica rapa subsp. sylvestris) is a persistent annual found in arable crops in Canterbury and Southland, and throughout New Zealand. Sometimes known as field mustard, the lower leaves have bristly hairs and are divided into pairs of lobes on the lower half of the leaf, whilst the upper part is one large terminal lobe. The upper leaves are smooth and lance-shaped. The flowers are bright yellow with four petals. The open flowers are at the top of the branched stems; the unopened buds below. The flowers later form linear pods.

Speedwell

Veronica persica

Speedwell (Veronica persica) is very common throughout New Zealand. Also known as scrambling speedwell, it is a sprawling, many stemmed annual with blue flowers. Germinates in both autumn and spring, so can be a problem weed in arable and brassica crops.