The classic, and true, definition of a weed is a plant in the wrong place. Every plant has its use and place, but in our gardens we want only our chosen ones to prosper¡ªnot those that just appear on their own. A weed may be any plant at all. So a lovely ground-cover plant such as oxalis, so suited to shady woodlands, becomes a weed when it gets among our vegetables, herbaceous borders, or greenhouses. Some grasses might be fine in the lawn, but not in the flowerbed next to them. Flowering plants become weeds if they self-seed everywhere or run and spread wildly, or outgrow or out-compete the more choice plants around them. In many ways even a big tree or climber, or a Leylandm or privet hedge (especially if it belongs to a neighbor!) is a potential weed problem.
Of course, not all weeds are a problem. If, for example, you want to encourage wildlife in your garden, then you may find that many weeds are beneficial in some way. However, they should still be controlled in most parts of the garden, since \ they can harbor diseases and pests. Any weed carrying a pest or disease may potentially spread it to our garden plants, especially if it is closely related to them.They also compete too well with our chosen plants for air, light, water, and nutrients. In order to control weeds, it really helps to know and recognize the different common types, where they occur and how they behave, so that you can deal with them most effectively.
What grows where naturally
Nature soon fills any bit of empty ground. Weeds, probably blown in by seed, will eventually grow in a pile of builder’s rubble and within a few years it will be covered. First it might be stinging nettles (Urtica dioica), then brambles (Rufrus spp.) and finally weedy tree saplings, such as sycamore or elder. Your lawn can go the same way. If you stop mowing, it will become a scrub and then a wood. And every plant on the way will be self-sown. Old and neglected gardens are therefore not full of just cultivated plants, but all sorts of weeds too. The type of soil and the degree of shade and moisture will determine which seeds will germinate. If the soil is poor and acid, it will have one set of weeds or wildflowers; if it is wet, rich or alkaline, then others will flourish. So a good sign of a rich, moist soil in a prospective garden is a really lush, thick stand of stinging nettles! Newly turned bare soil will grow a Hush of poppies (Papaver rhoeas) and nightshade (Solarium nigrum), if its seeds have long been buried. Soil that was once ahorse meadow will produce docks (Rumex spp.). Rich topsoil, freshly uncovered, as in a vegetable bed, will probably become covered with chiekweed (Stellaria media) and Cerastium spp., groundsel (Senerio vulgaris), and goosefoot (Chenopodium spp.).
