Weed of the Week: Dandelion (Taraxacum officinale)

Weed of the Week: Dandelion (Taraxacum officinale)

By Laurence Gale

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 6 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.

Some weeds may be harmful to the environment or noxious to your regional ecology. For example Japanese Knot weed (Fallopia Japonica) is fast becoming a major weed problem on road side verges and urban landscape areas, a very difficult weed to eradicate. It is very important to recognise weeds and seek effective controls methods to eradicate them from our facilities.

Weeds can also be used as an indicator of soil conditions. For example, knotweed and plantains both indicate soil compaction because they can maintain adequate root respiration at lower oxygen diffusion levels than other plants. Different weeds tolerate different soil conditions, some are alkaline loving and others acid loving. Getting to understand and recognise the physiology of these plants will help you become better turfgrass managers.

This week's weed is: Taraxacum officinale (Dandelion)

Scientific name Family Life cycle	Taraxacum officinale Compositae Perennial
Form / Appearance	Dandelion is a widely distributed perennial, herbaceous weed. Mature plants arise from a strong, deep taproot that exudes a milky substance when cut.
Roots	Dandelions have deep tap roots that can penetrate through most soil profiles.
Flowers	Dandelion flowers are yellow in colour and are formed on a flower spike, the flower turns into a seed head, producing thousands of air/wind borne seeds.
Leaves	Leaf margins are noticeably wavy, especially on older leaves. All leaves are basal, ranging from 50-300mm in length. Leaves are oblong in outline, sometimes sparsely hairy, deeply indented with lobes that point toward the centre of the rosette.
Reproductive method	Dandelion weeds depend on seed dispersal for reproduction. The yellow flower dies down to leave ripened seeds that are enclosed singly within fruiting bodies and are attached to a long slender stalk that terminates in a parachute-like structure called a pappus.
Habitat	Dandelions are able to establish in most turf grass situations and on most soil types. Dandelion populations have become significant in recent years , especially on local authority playing pitches, where little or no herbicide treatments have been applied. Dandelions are also a very common site on road side verges.
Miscellaneous info	The dandelion has long, lance-shaped leaves. The name is derived from its resemblance to a lion's tooth - Dent-de-lion in French. Dandelion leaves are eaten in salads and are an excellent source of vitamins and minerals. They are also a strong diuretic used traditionally to relieve water retention caused by heart disease.
Cultural Control	Dandelions can be mechanically or physically removed. 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 dandelions from establishing. Good soil fertility is essential, maintaining a soil pH of 6.5 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. Tritox (Contains 178g/L (16.2%w/w) MCPA 54.g/L(4.9%w/w) mecoprop-p and 15g/L (1.4%w/w) dicamba and potassium salts. Scotts. Intrepid 2. (Contains 20.8g/L dicamba,166g/L dichlorprop-p ans 166.5g/L MCPA). Scotts. Greenor. (Contains: 40g/L fluroxypyr, 20g/L clopyralid and 200g/L MCPA). Rigby Taylor. Bastion T. (Contains: 72g/L fluroxypyr and 300g/L mecoprop-p ). Rigby Taylor. Dormone (Contains 465g/L2,4-D(38.1%w/w) as the diethanolamine salt). A herbicide which can be used near water. Bayer Environmental Science. Supertox 30 (Contains 95g/L (8.8%w/w) mecoprop-p and 93.5g/L(8.7%w/w) as the diethanolamine salts). Bayer Environmental Science. 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. Herbicides are an effective tool where high quality turf is desired. However, they must be applied with care and accuracy and in the context of a good overall turf management program. Before using any herbicide, carefully review the label for conditions of use including rates, methods of application, and precautions. Never use an herbicide in any manner contrary to its label and be sure that the herbicide will not injure the turfgrass species