January 19, 2022

Weed or segetal plant - undesirable plant in crops (from the point of view of agriculture, forestry or fishing). Weeds usually grow wild in segetal habitats (farmland, meadow, pasture, etc.). Many formerly considered weeds are now disappearing plants, some (e.g. some flax weeds) are already extinct in Poland. The science of weeds and their control is herbology.

Definition of

The term weed is used in agriculture with reference to plants undesirable in the composition of agricultural cultivation, both in field and garden crops, as well as horticultural, greenhouse and meadow crops. In forest management, this concept functioned unofficially in relation to tree and shrub species not provided for in the target species composition of stands (e.g. hornbeam, aspen and birch) and in relation to plants hindering regeneration (e.g. sand reed). In fisheries, weeds are fast-growing, nuisance aquatic plants (e.g. Canadian marsh). In fisheries, there is also the concept of fish weed referring to the species of fish that are undesirable in a breeding or fishing area. The term "weed" is a relative term as the same plants may be desired in one place and not in another. For example, oats in wheat are weeds, but alone in the field are not. The opposite may also be the case - wheat as a weed in oats.

Ecological adaptations

Weeds often produce seeds that can stay dormant for long periods. They remain in this state until they are exposed to light or, for example, their shell is damaged. This allows weeds to germinate, for example in freshly plowed soil. Many species of weed-infesting cereal crops are speirochoric plants, for which the main way of spreading seeds is by dragging them along with the seed material. Weeds quickly adapt to a given crop and cultivation technique, they grow faster and more luxuriantly compared to a cultivated plant. The field weeds are mostly archaeophytes.

Division of weeds according to where they occur

In relation to plants considered to be weeds, the division based on the place of their most frequent occurrence is applied. There are, among others, weeds: segetal - associated with crops, growing mainly in fields, among cultivated plants, sometimes contributing to a reduction in yield. Segetal weeds create their own plant communities, different species and their compositions are related to specific conditions of the habitat and the species of the crop plant. Segetal weeds include e.g. cornflower, field tares, field delphinium, field poppy, sand poppy, field pimpernel ruderal - occurring near human settlements, often in places rich in nitrogen, near sheds, fences, etc. These plants are largely derived from fertile riparian forests and nitrogen-loving fringes. They create their own plant communities. These include, for example, burdock, nettle meadow - not eaten by animals grazing in meadows and pastures (e.g. nettle, thistle), difficult to digest or poisonous (spurge) and parasitic plants (hedgehog).

Weed harm

Negative effects of weeds: significantly reduce the yield of crops; they take away their space, light, water and nutrients, and can even completely obstruct cultivated plants many species of weeds, e.g. vetch, thistle make harvesting difficult, some cause lodging, preventing mechanical mowing Hard amaranth Palmer stalks can damage combine harvesters, while fibrous shoots of Velvetleaf brought to Poland cause blocking of machines used for beet harvesting weeds reduce the value harvested

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