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FROM ENCYCLOPEDIA:
Weed
A weed is an unwanted plant. The notion of "unwanted"
is of course entirely in the eye of the beholder. A weed in one
situation might be a wildflower in another. For example, some people
love dandelions for their yellow buttons, like gold coins on the
ground. Children enjoy blowing the puffball seed heads that form
on the dandelion, and adults might utilize the dandelion root as
an herbal medicine. In some areas, dandelion leaves, which are edible,
are sold in certain restaurants or grocery stores. Yet the caretaker
of a lawn will generally regard the dandelion as a troublesome weed.
It is typically necessary for a plant to grow easily to be considered
a weed because difficult to grow plants need to be nurtured and
are easy to remove without returning.
Plant Weeds
Many plants have become weeds by being transferred by human action
to locations where they have no natural grazing predators; and they
will compete with other plants for space. The classic case is the
prickly pear (Opuntia stricta), which overran vast areas of Australia
until a moth (Cactoblastis cactorum) was introduced, eliminating
more than 90% of the prickly pear infestation within 10 years. This
case is frequently cited as an example of successful biological
pest control.
In cases like the prickly pear in Australia, the weeds are termed
invasive species (or exotic invasives). This term is applied when
a plant is an introduced species that invades and disturbs natural
ecosytems, displacing species native to the target ecoregion and
causing harm.
Plants that are often considered weeds
Cleaver, Crabgrass, Dandelion, Daucus, Diffuse knapweed, Dock,
Eucalyptus, Giant salvinia, Gorse, Goutweed, Hairy Vetch, Henbit,
Japanese knotweed, Johnson Grass, Kudzu, Milkweed, Mullien, Plantain,
Quackgrass, Ragweed, Red deadnettle, Rubber vine, Shepherd's purse,
Sicklepod, Sunflower, Thistle, Tufted Vetch, Tumbleweed, Water hyacinth,
White ginger, Wild onion
(from wikipedia - free encyklopedia) |
