Californian Thistle

Cirsium arvense

Californian thistles (Cirsium arvense) are a perennial thistle that is a major weed of pastures and crops throughout New Zealand. It grows and spreads in patches with a spreading underground root system. In the winter the foliage dies off from frosts with new plants growing from the underground root system in the spring. The root system is easily broken up by cultivation but new plants originate from these and can be very problematic in crops and new pastures.

Cotyledons:

Wide
Apex rounded
Stalkless

Leaves

Oval
Notched with prickles

Related Pests

Cleavers

Galium aparine

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.

Ryegrass - Annual

Lolium multiflorum

Annual ryegrass (Lolium multiflorum) is an important cultivated grass species which becomes a very competitive weed when growing in cultivated crops. Generally germinating at the same time as the crop it grows quickly and competes aggressively for space, light, nutrients and water. Uncontrolled annual ryegrass will significantly reduce yields. To identify look for young plants between the crop rows, young plants are upright and the leaves have prominent veins. As plants get bigger the leaves are shiny underneath and these stand out, especially on breezy days. Later, when in ear look at the seedhead as ryegrasses have one edge of the seed against the axis which means the flat side of the seed is visible.

Ryegrass - Perennial

Lolium perenne

Perennial ryegrass (Lolium perenne) is an important cultivated grass species which becomes a very competitive weed when growing in cultivated crops. Though it is a perennial species it will still produce seed in the first year of growth. Generally germinating at the same time as the crop it grows quickly and competes aggressively for space, light, nutrients and water. Uncontrolled perennial ryegrass will significantly reduce yields. To identify look for young plants between the crop rows, young plants are upright and the leaves have prominent veins. As plants get bigger the leaves are shiny underneath and these stand out, especially on breezy days. Later, when in ear look at the seedhead as ryegrasses have one edge of the seed against the axis which means the flat side of the seed is visible.