A weed is simply a plant that is growing where it is not wanted. But why are they considered such pests? Here are some things you didn't know about weeds.

Wily weeds
There are many ways in which they succeed in popping up in the most inconvenient of places:
by growing very fast, often smothering other plants to get the most light, minerals and water
by producing lots of seeds and having lots of different ways of spreading them around
by germinating their seeds quickly
by producing seeds that survive over several years
by having effective defence systems that protect them from being eaten by animals or picked by people, for example, stinging nettles
by multiplying in more ways than one, usually making new plants along their stems

Interesting facts
Stinging nettles are often used in herbal medicine for cleaning the body and making the heart work better. Nettles are packed full of vitamin C and new shoots are often used to make tea.
There are many superstitions linked to weeds. For example, if you hold a buttercup under your chin and a yellow shadow appears, it means you like butter. Or, finding a four-leaf clover brings good luck. And if you touch a dandelion you will wet the bed! The French word for dandelion is Pissenlit, which directly translated means 'wee in bed'. Weeds such as wild carrot, cow parsley and celery grow at least 350 seeds on a single flower-head. Wild clematis grows climbing, sprawling stems up to 30m long (100ft) - that's about 20 people from top to toe!