Research
Weeds in the garden
Perennial weeds in lawns
Creeping and rosette-forming weeds which survive close mowing can be controlled by selective growth-regulating lawn weedkillers. These are applied from April to August when grass and weed growth is vigorous. Most formulations are based on 2,4-D or mecoprop. Some weeds are killed by a single application but a few may require repeated treatment. Lawn weeds are one subject in Advice section.
Mosses
Mosses become established in lawns when grass vigour is reduced, under conditions of poor drainage, compaction, shade, excessively acid soil or close mowing. Treatment can be carried out at any time of year when weather is mild and the soil is moist, particularly during September and February or March. Mosskillers are based on dichlorophen or cresylic acid. They are contact in action with little or no residual effect, and moss will usually return if cultural measures are not implemented. Lawn sands are based on ferrous sulphate.
Beds
Light hoeing is recommended for control of weeds in new beds. Annual application of mulch will help reduce annual weeds and aid the removal of perennial weeds. Broad-leaved perennials such as bindweed, ground elder or horsetail can be controlled with glyphosate applied as a directed spray or spot treatment, when weeds are actively growing. Dichlobenil can be used around established roses and some trees and shrubs to control some perennials and annuals, but check manufacturer’s lists for intolerant species.
Vegetables
Perennial weeds do not survive under regular cultivation, but there is often a large amount of weed seeds in the soil which are brought up to the surface with cultivation. These can be controlled by cultivation when not under crops, or by adopting a stale seedbed technique. Prepare the seedbed 10 to 14 days before required. Allow weed seedlings to germinate which can be killed by hoeing. Then vegetables can be sown with minimum disturbance to the plot.
Paths and drives
In March apply a proprietary path weedkiller containing a mixture of herbicides with contact and persistent action.
Care must be taken when storing and applying weedkillers to avoid contact with other desirable plants. It should be noted that weedkiller applied on a patio may affect tree roots growing under the paving. Information on the signs of weedkiller damage is given in RHS Help & Advice. Always read the label.
For more information on controlling weeds in the garden, please refer to the Advice section.
Invasive non-native species
The uncontrolled spread of plants in the UK which have been brought in from abroad for ornamental purposes is discussed in a recent report from the Science departments:
Invasive non-native species (37KB PDF)
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At war with aliens, Plantlife report on alien plant introductions
Further reading
This is just one topic covered by the Society's monthly journal for members, The Garden, and recent articles of interest are listed below. The latest thinking from the best minds in horticulture today is to be found in the RHS journal, The Plantsman: some recent relevant articles are suggested here.
Anon. 1999, November. Dangerous plant. The Garden (RHS) 124(11): 811. Hydrocotyle americana, a new alien weed.
Perring. F. 1996, June. The hidden invasion. The Garden (RHS) 121(6): 360-362.
Rees, Alun 1995. Allelopathy: inter-plant relationships. The New Plantsman 2(2): 103-105.