Weeds are opportunistic and are virtually impossible to eliminate from turf. An appropriate weed control program limits weed infestations rather than attempting to eliminate them entirely. Weeds will soon invade weak stands of turf that lack density. In some situations, extremely competitive weeds can invade dense turf grass. The only effective approach to control weeds in turfgrass is to combine chemical weed control with an appropriate Turf Grass Management program directed at improving turf grass density and vigour appropriate Turf Grass Management includes appropriate mowing, watering, fertilizing and cultivation.

Grasses. These weeds are distinctive in that grasses are monocots. They have leaves with parallel veins and only one seed leaf in a developing seedling.

Sedge is neither a grass nor a broadleaf they are often found growing on waterlogged acid soils or soils of poor fertility. Yellow nut sedge is the most prominent weed in this group. It has a grasslike appearance with a distinct triangular stem, a deeply keeled midrib and no collar or ligule.

All weeds go through a cycle of seed germination, foliar and root growth, maturity and flowering, and seed development. You must understand weed life cycles because the effectiveness of herbicides depends on the stage of growth of a particular weed. For example, pre-emergence herbicides are effective only when applied before weed seeds germinate in the spring or autumn. Post emergence herbicides are most commonly applied on weeds found in turf, they are however much more effective when applied to weeds in a juvenile vegetative stage of growth rather than at a mature flowering stage of growth. If post emergence herbicides are applied to mature weeds, applications should be made in spring or early summer preferably when the temperatures exceed 20 degrees centigrade.

Plants that live for one year only. Seed germinates in the autumn, the weed matures through the winter, sets seed and dies in the spring.

Summer annuals
Plants that live for one year only. Seed germinates in the late spring and early summer, the weed matures very rapidly in the summer and sets seed and dies in the autumn.

Winter perennials
Plants that live for several years putting on most of their growth in the winter months flowering and setting seed  in the late winter or early in spring.

Summer perennials
Plants live for several years, which put on most of their growth during the summer months, they mostly flower and set seed in the summer or autumn

Biennials
Plants that live for two years, which put on most of their grow during the first summer, they tend to flower and set seed then die in the second summer.

• Are there herbicides that can effectively limit the growth of the weed, and can the herbicide be safely used without harming other plants or the environment?

• Do I have the knowledge and equipment to safely handle, apply and store herbicides?

If possible determine the cause of the weed problem and design a management program to increase turfgrass competition and reduce weed competition.

Correct obvious major problems such as, poor soil fertility, soil compaction, traffic patterns and poor drainage that may be causing the weed problem.

When needed, safely apply herbicides so that weeds may be controlled and turf may resume a competitive density.

Cultural weed control

The basic principle involved in cultural weed control is to grow a stand of grass that is dense and competitive enough to prevent weed envasion.

Weeds require light, water and nutrients to grow. As turf loses density, light will penetrate the canopy and cause weed seeds at the soil surface to germinate. Once germinated, weeds can develop rapidly, especially if the turf continues to decline.
Weeds will probably receive sufficient light to develop if one can see bare soil when looking straight down on a stand of grass. Good Turf Grass Management practices that discourage turf weeds include proper mowing, watering, fertilizing, thatch control and cultivation. Using locally adapted turf grasses and establishing them during the correct season of the year can reduce the opportunity for weed invasion.

Mowing
To prevent weed germination, mow frequently at the tallest recommended mowing height. Weeds germinate rapidly when turf is scalped, by mowing too short or when it is not mowed frequently enough. Both mistakes decrease turf density and cause an open canopy that favours weed invasion. Experts recommend a range of mowing heights to meet specific turf activities. Lower mowing heights require more intensive Turf Grass Management. Each mowing should not remove more than one-third of the total leaf height. Annual grassy weeds are especially a problem on turf that lack density as the result of poor mowing.

Soil Fertility
Areas that receive chemical weed control but no application of a balanced fertilizer are probably being mismanaged. Even in low- maintenance situations, the first defence against weeds is dense turf. For cool-season grasses (Bent, perennial rye, fescue), apply a high nitrogen, high potassium balanced fertilizer in the autumn. For warm-season grasses, (Cynodon dactylon, Pennisetum clandestinum) apply it in the summer. Additional fertilizing with a balanced lawn fertilizer should be applied during the growing season to provide adequate growth and density with less attention given to turfgrass colour. On cool-season grasses avoid heavy applications of high nitrogen fertilizer in the spring, which will encourage excessive vertical leaf growth, bringing with it a greater chance for fungal diseases and insect pest attack.

Establishment
Weeds can prevent the establishment of turf grasses at certain times of the year, late summer and early autumn are preferred for establishment of cool-season grasses. Cool-season turf grasses that have germinated by early March will not be affected by summer weeds and will usually establish a competitive stand of grass before winter annuals become a problem.

Thatch and cultivation
These have a dual effect in terms of weed control. Weed seeds below a thatch layer lack the necessary light for germination, so weed seeds generally do not germinate in the thatch layer or when they do usually die because of the poor environment for seedling development in thatch. In this respect, thatch provides some degree of weed suppression. On the other hand, thatch can cause turf decline by harbouring disease-causing pathogens, reducing water infiltration and tying up pesticides and fertilizers. Power raking and verticutting are typically used to remove thatch.

Soil compaction
Soil compaction from traffic and tight soils will often decrease turf competition in favour of some weeds, especially Eluesine indica (Goosegrass). Two ways to fix the problem are coring and slicing and the topdressing with sand. These procedures improve the soil surface and the growing environment for turfgrass.

Chemical weed control
The appropriate application of herbicides can dramatically reduce turfgrass weed populations in a short period of time. A combination of their cost effectiveness and simplicity of use often makes herbicides the primary means of weed control with little attention given to other weed reduction measures. Remember, herbicides are only one facet of the total weed control puzzle. Effective long-term weed control and a reduction of pesticides in the environment will be achieved only when an effective cultural weed control program has been implemented.

Selective herbicides kill only the target weed species, leaving the turfgrass unharmed.
Selective herbicides are further divided into their type of application. Re-emergence herbicides are applied before the emergence of a weed. Post emergence herbicides are applied after a weed has emerged; they are generally applied to weed foliage.