What is a weed?

By definition a weed is a plant that is growing in the wrong place. Weeds take valuable space, water, sunlight and nutrients that may otherwise be accessible to important crops, in our case turf grasses. Weeds not only compete for these resources they can disfigure and cause problems to playing surfaces.

Weeds are very good competitors and take advantage of any opportunities to colonise turf situations, particularly when the sward is under stress and weak, leaving bare soil areas for weeds to populate.

Weeds have many mechanisms and characteristics that enable them to do this, having thick waxy cuticle leaves that can be resistant to some chemicals, fast reproduction methods, the ability to reseed in six week cycles and deep tap roots enabling the weed to survive in compacted dry ground conditions.

Weeds have one of three life cycles: annual; biennial or perennial.

Annual weeds: Live for a single season. These weeds germinate from seed in the spring or summer, flower and then die.

Biennial weeds: Live for two seasons. During the first growing season, these weeds remain in a vegetative stage and, in the following year, produce flowers, set seed and die.

Perennial weeds: Live for multiple seasons and flower more than once. Perennial structures (rhizomes, stolons, crowns, entire plants or roots) survive from year to year.

One perennial weed that evades and colonises outfields and sports fields is White Clover (Trifolium repens). The word Trifolium means three leaflets on each leaf.

White clover is a short-lived perennial that can reseed itself under favourable conditions. It grows rapidly and spreads via stolons. Clover has leaves that are usually palmately to semi-pinnately, divided into three leaflets. The leaflets are entire or shallowly toothed. Stems are low-growing, prostrate, usually without hairs, but sometimes with short hairs, ranging from 100-400mm in height. Stems root at the nodes. The trifoliate leaves and white flowers are both key features that help in the identification of this weed.

White clover has a shallow root system, which makes it intolerant of dry soils. It grows best during cool, moist weather on well-drained, fertile soils with a pH between 6 and 7.

The clover family has flowers in mostly dense, rounded clusters, with colours ranging from white, yellow, or pink to red or purple. It is fertilised through pollination by insects such as the honeybees and bumblebees.

There are nearly 300 species of clovers worldwide, mostly of the North Temperate Zone.

Cultural Control: Established clover colonies are difficult to remove by hand. Care should be taken to ensure that all roots are thoroughly removed. Close mowing prevents seed head formation, whilst maintaining a dense sward will deter or prevent clover from establishing. Good soil fertility is essential, maintaining a soil pH of 6 to 7.

Chemical Control: Apply selective broadleaf herbicides when plant growth is active. There are a number of products available for controlling broad leaf weeds in established turf.

These chemicals are best used when the weeds are actively growing, usually between April-October.

Spearhead Herbicide - MAPP no. 9941 Active Ingredients: 20g/l (1.72% w/w) clopyralid, 15.9g/l (1.45% w/w) diflufenican and 300g/l (25.9% w/w) MCPA.
Scotts Re-act Herbicide - Mapp No. 12231 Active Ingredients: 56.25g/l (22.6% w/w) MCPA, 237.5g/l (20.9% w/w) mecoprop-P and 31.25g/l (2.8% w/w) dicamba as the dimethylamine salt formulated as a soluble concentrate.

Headland Relay Turf Herbicide - Mapp No. 08935 Active Ingredients: 200g/L Mecoprop-P, 200g/L MCPA and 25g/L Dicamba.

New Estermone Weed Killer - MAPP no. 13792 Active Ingredients: 200g/litre 2,4-D as the iso-octyl ester and 35g/litre dicamba.

These herbicides are usually applied as a liquid using watering cans, knapsack sprayers and vehicle mounted sprayers.

Ensure you follow manufacturer's directions, health & safety and product data sheets, and comply with COSHH regulations when using these chemicals.