By Kate Wall
A large part of a well-kept lawn is weed control. Good weed management does not rely entirely on weed control products, however there is a time when these products are necessary. There are plenty of different types of products available to the home gardener to assist in controlling lawn weeds.
Knowing which product to use when is not always easy. The following information will assist in understanding weed management for lawns, and when to use weed control products.
Maintaining a healthy lawn with an appropriate mowing regime will be the most important defence against weeds. A healthy lawn is able to out compete weeds and does not have bare patches which are available spaces for weeds to take hold. Bare patches in a lawn, usually created through poor mowing or excessive wear and tear are the perfect entry points for weeds to become established in a lawn.
The first step in eradicating weeds from a lawn is improving lawn care. This will give advantage to the lawn grass over the weeds. This applies if you are planning to care for your lawn organically or conventionally. Addressing soil quality including compaction and nutrient depletion will be critical in creating a healthy weed free lawn. Poisoning weeds without addressing soil issues is likely to leave the lawn grass just as disadvantaged and the weeds are likely to take hold again before the grass can fully recover.
Many weeds such as nut grass, and the deep rooted lawn weeds such as dandelions will favour compacted soils which are low in calcium. The deep root allows them to access minerals from deep in the soil which are not available to the lawn grasses more shallow roots. When these weeds are dominant, the soil should be aerated and then treated with a complete fertiliser which is high in calcium and other minerals. Organic matter should also be added to improve the soil structure. This can be done by top dressing with a sand / compost mix after aerating.
Lawns which have heavy infestations of leguminous weeds such as clover, burr medic, creeping indigo, tick trefoil or anything with pea like flowers are likely to have soils which are low in nitrogen. Fertilising these lawns regularly with small amounts of high nitrogen fertiliser will encourage the grass to out compete the leguminous weeds.
An abundance of chickweed and sow thistle can indicate that the soil is overly rich and moist, in which case you can reduce the fertiliser and water you are giving the lawn.
Weeds which have large flat leaves such as dandelion, flat weed or plantain tend to be able to dominate a lawn which is being mown too low. Mowing too low can create bare spots through scalping the lawn which in turn provides entry points for weeds to establish into the lawn. Correct mowing height and frequency are crucial elements of weed management. You can find out more about good mowing techniques here.
Mowing needs to be done frequently enough to prevent weeds from setting seed. Once the weeds have gone to seed, those seeds can remain dormant in the soil for many years, waiting for the right time to grow. By spraying the freshly released seed with a product called 'Weedless” from Earthlife, you will greatly reduce the amount of seed which them germinates.
Weedless is a safe product to use on lawns that have children and animals on them. It is a compost enzyme which prevents seed from germinating. It will reduce seed germination by up to 70%, do a repeat spray is advisable where there are many seeds present. It acts on contact with the seed and is not residual nor is it a poison. It is safe to spray on all grass types as it does not harm plants at all, only seeds.
Oxa Pro is a lawn fertiliser which contains a pre-emergent herbicide in granular form. This herbicide remains in the soil without having any effect on living plants. It is useful in lawns which have significant weed seeds, as it acts on the new plants once the seeds begin to grow.
Once soil improvement and good lawn care practices have been put into place, any further weed eradication activities will be far more effective. For small infestations this may involve hand pulling the weeds, for larger infestations spraying a lawn specific herbicide may be required.
More information regarding specific lawn herbicides can be found here.
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