Weeds, Can We Win?
Speaker: Alick Jones
Date: 29th January
A weed is by definition a plant in the wrong place at the wrong time. Many so-called weeds are useful e.g. Rhododendron was introduced as a decorative plant, the seeds of Groundsel and Michaelmas daisies are food for Goldfinches, you can eat ground elder, yellow rattle weakens grass and makes less mowing.
Bad effects of weeds
- Don’t look nice
Competition for nutrients, water and air e.g. bindweed
Offensive e.g. stinging nettles, the short hairs are irritant and the long hairs are toxic, ragweed is toxic to grazing animals like horses and can be irritant to people when pulled up (wear gloves), Euphorbias e.g. spurge produce toxic white sap (again wear gloves), Lords and ladies are poisonous, but taste really nasty so not swallowed, deadly nightshade poisonous. Thistles are very prickly.
Don’t look nice, weeds make borders look untidy and prevent the wanted plants showing to their best advantage.
Weeds are divided into two categories
e.g. scarlet pimpernel, bitter cress (a relation of the wallflower). These plants may have 2/3 cycles in a year. They are successful as they reproduce rapidly as in the wild they live in soils that are disturbed. They produce huge numbers of seeds – groundsel may have as many as 1,000 seeds per plant and the seeds can remain dormant for many years e.g. ragwort seeds last for 20 years, poppy seeds for 50 years. It is estimated that one acre of arable land may contain 113 million poppy seeds.
These seeds will start to germinate when exposed to light e.g. when digging, ploughing etc. Annual weed seeds are dispersed by the wind e.g. parachutes of dandelions, rosebay willow herb and spear thistles. They can also be transported by animals e.g. burdock has hooks, goose grass, on shoes of humans or feet of animals, or in droppings of birds e.g. mistletoe or humans e.g. tomatoes. Many weeds have explosive seed pods that release the seeds long distances e.g. cranesbill which has a range of 6 metres.
These die back in winter and have various ways of surviving the cold e.g. long roots that store food for next year e.g. dock roots are 6.5 metres long.
Minimising the effects of weeds
- Prevention e.g. mulches, black fabric and ground cover plants
- Remove – do it now before they get too big. Use a hoe, hand fork or pull up by hand