Chickweed

Though barnyard grass (Echinochloa-crus-galli) is mainly found on the North Island it can now be found on the South Island as far south as South Canterbury. Barnyard grass germinates in the spring when temperatures increase. Barnyard grass is very competitive and invades a range of crops. When small, barnyard grass can be identified by its upright habit, rolled leaves and lack of ligules or auricles. When seed-heads are present they are quite distinct being open and with dark brown seeds.

Annual poa (Poa annua), also known as annual meadow grass, is a fast growing annual grass found throughout New Zealand in a wide range of crops. While individual plants tend to be small, populations of this grass weed tend to be large and they then compete for light, nutrients and water. Poa annua is best identified by the boat shaped tips to its leaves and the two parallel veins (often referred to as tramlines) that can be seen if the leaf blade is bent backwards. Germination takes place throughout the year and is set very quickly meaning populations soon increase.

Cleavers (Galium aparine) are a common, widespread annual weed found throughout New Zealand. A significant weed of cereal and horticultural crops and often found scrambling up fencelines and hedgerows Cleavers have a scrambling, clambering growth habit and “stickiness” due to tiny hooks on its stems and seeds.

Cornbind (Fallopia convolvulus) also known as Black-bindweed, is a climbing, spreading vine that grows to 1 – 1.5 m long with stems that twine clockwise around other plant stems. The leaves are arrow-shaped up to 9 cm long by 6 cm wide. The flowers (November to April) are pale green, small and grow in clusters closer to the ends of the stems. Seeds are triangular and shiny black. Cornbind is more commonly found in the South Island (South Canterbury), but is showing up increasingly in cultivated areas in Hawkes Bay and Wellington.

Fathen (Chenopodium album) is one of the most serious weeds of cropping throughout New Zealand. It is an annual that germinates in the spring and early summer and then dies off in the autumn with frosts. Fathen is an extremely vigorous weed that can quickly outcompete and smother crops. An upright plant that can grow to 2 m tall and is a prolific seeder.

Fumitory (Fumaria muralis) is a weak-stemmed scrambling and climbing annual weed with pink tubular flowers. It is common throughout New Zealand and is a significant weed of crops (especially cereals) as it can smother crops if not controlled.

Nettle (Urtica urens) is present New Zealand wide except for Northland, Taranaki and Westland. It is well known as stinging nettle due its characteristic of causing swelling and stinging to the skin upon contact. The erect 60 cm tall annual is often found on farms in stock camps where it needs bare ground to germinate. Animals will not graze it. Nettle can also be a troublesome weed in cropping and horticulture.

Shepherd's purse (Capsella bursa-pastoris) is a rosette annual with distinctive flower stems that grow to 30 cm high. It is very common throughout New Zealand in cultivated soil and is conspicuously present in the winter although it can germinate at any time through the year.

Sow thistle (Sonchus oleraceus) is common throughout New Zealand in crops, gardens and waste areas. It is an annual that starts as a rosette that develops a tall, leafy and succulent stem with yellow flowers up to 1 m tall. The leaves are often collected and cooked as a vegetable (puha) in New Zealand.

Spurrey (Spergula arvensis) is a fine-stemmed, sprawling annual weed which is commonly found throughout New Zealand. It can often grow dense. Severely competing with and smother crop seedlings and establishing pastures. Spurrey germinates in the autumn and spring.

Wild Oats (Avena fatua) Wild oats are a common and very damaging weed that can occur in many crops. Capable of germinating at any time of year, they will just as successfully grow and compete in winter cereals as in a spring planted crop like peas. Left uncontrolled wild oats will quickly grow into large, multi-tillered, competitive grass weeds. Due to their competitive nature very few plants per square metre are needed before it becomes economic to control them. Depending upon the crop controlling 5-10 wild oats per square meter will result in an economic response. Wild oats also produce a large number of long-lived seeds, often as many as 150 per panicle with many panicles per plant. Wild oat seeds can remain viable in the soil for several years and the common saying “one year’s seeding, 7 years weeding” stands very true for wild oats. Wild oats can be successfully controlled with selective herbicides such as Puma S. However, if numbers are low hand rogueing should be undertaken if possible.

Wild portulaca (Portulaca oleracea) is a fleshly annual weed that has a prostrate habit, spreading out to 30 cm wide. It has characteristic reddish stems with yellow flowers. It is frost sensitive so it only grows in the summer and prefers sunny open situations. It is common in the upper North Island and more occasionally further southwards.

Black nightshade (Solanum nigrum) is a significant weed in arable and horticultural crops but it is also common in disturbed pasture. Black nightshade is present throughout New Zealand but less so in the lower South Island. Distinctive black berries (7-10 mm) can be found on mature plants.

Groundsel (Senecio vulgaris) is an annual weed, found throughout New Zealand. It is a common weed in arable and horticultural crops, gardens and waste areas. The erect weed grows to 50 cm tall with soft, leafy stems and distinctive yellow flowers.

Twin cress (Coronopus didymus) is very commonly found throughout New Zealand. It is an annual weed that germinates in the spring and autumn. As a seedling it is a rosette that develops a scrambling habit out to 40 cm. Twin cress is common in cultivated ground, crops and open pastures. Can cause significant issues on dairy farms as it can taint milk.

Willow herb (Epilobium nummulariifolium) is an upright erect growing perennial that is found throughout New Zealand. It prefers moist situations and can be a problematic weed in orchards because of its tolerance to glyphosate.

Willow weed (Persicaria maculosa) is an erect and sprawling summer growing annual that can be a serious weed in crops (e.g. maize). It has reddish stems and pink spike like flowers. It is common in the spring and summer throughout New Zealand but is quickly killed by frosts. A similar species, water pepper, grows taller and is common in wet places.

Henbit (Lamium amplexicaule) is commonly present in cropping areas in the South island. It is a slender annual that grows to 30 cm tall with purple whorl shaped flowers.

The two most common species, narrow (Plantago lanceolata) and broad-leaved (Plantago major) are very common throughout New Zealand. They can be found in arable and horticultural crops but are abundant in low fertility pastures and lawns. Plaintains are rosette perennials with upright flower stems. Recently, they have been included into pasture mixes as they are very palatable to stock and considered to have health benefits for grazing animals.

Scentless Chamomile (Matricaria perforata) is a bushy annual or biennial plant that grows to 60 cm and is wholly or almost scentless. It has an erect stem, with branches only from mid stem upwards. The leaves are fern like and sticky. The flowers are large, with twelve white petals, with central yellow disc florets, giving the flower a daisy-like appearance. They appear singly on stems and branches between December and March. Found in moist disturbed areas such as roadsides, cropland, pasture, drainage ditches and waste areas. The seeds are 2 mm, dark brown with a raise edge, and each plant produces 10,000 - 200,000 seeds which germinate in shallow soil.

Stinking mayweed (Anthemis cotula) is an annual weed common in the North Island and also in Nelson, Marlborough and Canterbury. It has an erect, bushy growth up to 40 cm tall with white flowers with yellow centers. It germinates in the spring and is common in crops, disturbed ground and thin established pastures. As its name suggests when crushed stinking mayweed has a very strong distinctive smell.

Storksbill (Erodium cicutarium) is an invasive, sticky, hairy plant which grows in rossetes up to 30 cm across. It is widespread throughout New Zealand in drier coastal and lowland areas, and found in pasture, grassland and arable land. The leaves are pinnate, resemble ferns, and are divided into pairs of leaflets. The flowers are a mauve-pink colour, have five undivided petals, and are arranged in loose clusters on reddish coloured hairy stalks. Flowering is September to May. The seeds are contained in a long seed-pod which resembles the bill of a stork. When ripe the seed-pod bursts open into five strips, launching the seeds like little parachutes, or by means of the strips which have seeds attached to them, burying themselves into loose soil.

A hairy perennial that grows to 1m tall, White Campion (Silene latifolia) have stalkless upper hairy leaves in opposite pairs. Leaves are oval with pointed tips. The flowers grow in clusters and each flower has five bi-lobed white petals. Male and female flowers are on different plants The calyx is long and inflated, pale green in colour sometimes with brownish-purple veins showing, but narrower than that seen in Bladder Campion. White Campion is found in Wellington and most parts of the South Island on waste areas, arable land, pasture and river-beds.

Wild radish or Charlock (Raphanus raphanistrum) is a rapidly spreading, invasive, frost hardy plant found throughout New Zealand, except in Taranaki. Annual or biennial, it is usually found growing on roadsides, waste grounds and disturbed ground. It grows to 80 cm tall, and during October to April has white yellow or lilac flowers 15-20 mm with 4 petals. The leaves and stems are dark green, rough and bristly. Pods develop up to 6 cm long, containing 5 to 8 seeds which can break into individual sections.

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. 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) is very common throughout New Zealand, 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.

Wireweed (Polygonum aviculare) is a widespread annual with wiry, trailing stems that form mats up to 1 m in width. Wireweed 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.

Commonly known as redroot, amaranthus (Amaranthus powellii) is a serious weed of maize, other crops and orchards and is widespread throughout New Zealand. It can grow up to 1 m in height and is characterised by red coloured stem.