Lawn weed killer application
Selective weed killers or herbicides are used to control weeds on the lawn without harming the grass.
Many of these products will contain more than one ingredient, this is so they cover a broader spectrum of weeds, as no single ingredient will kill all types and species of weeds found in the lawn. Common ingredients used in weed killers include 2,4-D, dicamba, mecoprop -p, clopyralid, flurixypryr and MCPA.
A lawn weed killer may have different modes of action. At least one of the ingredients will be a foliage applied translocated herbicide, which effect the growth pattern of the weed. Selective weed killers are taken in the plant, mainly be the leaves and sometimes the roots. The chemical travels through the entire weed.
When a selective weed killer has been applied a twisting effect of the leaves and distorted growth can be witnessed. However it can take up to 6 weeks for the weed to die completely.
A word of warning: Do not confuse total weed killers with selective weed killers. A total weed killer will kill everything, including the grass and are not to be used on a lawn.
Lawn weed killer formulations
A lawn weed killer is available as a both liquid and granular products. Granular weed killers are mostly incorporated with a fertiliser (weed and feed), while liquids are not, although there are a few exceptions to this.
Getting the best results from a lawn weed killer
Like most products used on the lawn, they are only effective if they are used correctly and weed killers are no different. There are number of tips that can help you obtain optimum results when using a weed killer on your lawn. The following advice is primarily for a liquid weed killer that is too be applied through a sprayer. We believe this is most effective way of controlling weeds in the lawn.
Selective weed killers work best when the weeds are growing strongly, usually between April and September. In a typical British summer the ideal time for treating weeds is usually during May or June. This when growth is at its strongest.
Applying a nitrogen based fertiliser (to encourage strong growth) shortly before you treat the weeds will also help increase the effectiveness of the weed killer product. This technique is often used by turf care professionals.
If you are using a feed and weed product there is no need to apply a fertiliser prior to treatment as these products already contain fertiliser.
When carrying out weed control, don't mow the lawn at least 3 days prior to and 3 days following the treatment. Leaving the lawn for 3 days allow the weed to develop a large leaf area. This allow more chemical to stick to the leaf and be absorbed into the plant, thus improving the effectiveness of the lawn weed killer.
Leaving the lawn a further 3 days improves the uptake of the chemicals as it allows it travel through the whole of the plant and down to the roots.
Spray during suitable weather and ground conditions. Choose a dry day that is relatively still to avoid the chemical drifting onto non-target plants. It is also important that there is no rain forecast as this can wash the chemical of the leaves of the weeds and reduce the effectiveness of the weed killer.
It is also important to spray when the leaves of the weeds are dry. This will help reduce run off and the chemical has a better chance of sticking to the leaves of the weeds.
Remember clippings from the first 2 of 3 mowings following application may contain traces of chemical and should not be used for composting.
Avoid treating weeds during drought conditions and frosty conditions.
In many cases weeds may only be causing problems on localised parts of the lawn. If this is the case spot treat or only spray where the weeds are growing. This helps prevent unnecessary chemical wastage and is better for the environment. Small hand help weed guns are available for this type of treatment.