Identifying Garden Weeds: Know Your Weeds
Learn to recognise some of the more persistent and troublesome weeds in the garden and you’re half-way to eradicating them.
A weed is simply any plant growing where it’s not wanted. Native wild flowers and grasses are generally regarded as weeds whenever they appear among cultivated plants, though some gardeners may actively encourage them in a ‘wild garden’. Blackberries are welcome in the fruit garden, but are enemies in the flower border. Equally, some cultivated plants become weeds when they grow too vigorously for their allocated site — snow-in-summer (Cerastium tomentosum) is a charming rock garden plant, but will quickly smother its neighbours if left untrimmed.
Weeds become a problem when they compete with ornamental plants or food crops, reducing the available nutrients, light, water and space, and interfering with the garden’s visual appeal. They may even harbour pests and diseases.
Most common weeds have one distinct advantage over garden plants — they are native to the country, rather than introduced from worldwide locations, and are best adapted to the local environment. They often germinate and establish faster than introduced species, so you must get rid of them quickly.
A predominance of certain weeds can be an indicator of soil type — for example, sheeps sorrel and field woodrush on acid soils; corn marigold, small nettle and ironweed on sandy soils; cornflower and wild carrot on chalk soils. But the most troublesome and commonly encountered weeds, such as ground elder and couch grass, will be found on all types of soil.
Annual weeds live for just one year. They produce seeds that lie dormant over winter then germinate in spring or summer. Some can even produce two or three generations a year — in fact, the main problem gardeners have with annual weeds is their capacity for shedding seeds. One of the worst of all, fat hen, produces around 3000 seeds on an average plant, while a chickweed seed may remain alive buried in the soil for more than a quarter of a century before germinating on being brought to the surface by cultivation. They may be spread around the garden in mud on your shoes, by wind, on animals’ fur, in bird droppings or in composts.
Perennial weeds are often the most difficult to get rid of. Many multiply by creeping stems, either above ground or below, as well as by seed. New plants are also produced from tiny pieces of roots or underground stems which become severed during digging or hoeing. When turned over with the soil, they remain unnoticed until vigorous well-rooted shoots spring up everywhere.
Docks and dandelions are able to withstand longer periods of drought than most cultivated plants since their long tap roots penetrate the soil deeply to obtain water. Some plants, such as bindweed, may send down roots as deep as 3m (10ft), but others have relatively shallow rooting systems.