What are the characteristics of weeds ?

Written by Administrateur Modified on the 05/10/2011

Morphological and/or physiological likeness with cultivated plants
- “Mimicry”: no or little difference from the cultivated plant ; specially in, early stage (weed rice in irrigated rice cultivation).
- Tolerant or resistant to herbicides ( Euphorbia heterophylla or Commelina benghalensis in cotton cultivation).
Maturity of seeds synchronous to the crop harvest (weed rice or Rottboellia cochinchinensis in rice cultivation)
Polymorphism of seeds and of the germinal from requirements ( Commelina benghalensis produces 4 types of seeds with, each, a different level of dormancy)
Discontinued germination for long periods (the germination of Ipomoea eriocarpa seeds is possible all along the rainy season).
Seed dormancy and longevity in the soil (the seeds of Striga hermonthica can live up to 20 years in the ground)
Inducted/innate dormancy (in the sudano-sahelian region the seeds of Cucumis melo germinate only from May to July whatever be the conditions).
Adaptation to husbandry practices
- Multiplication through rhizomes or other vegetative propagation method, favoured by the soil cultural practices, specially disc ploughing ( Cyperus rotundus, Imperata cylindrica…)
- Propagation by cuttings ( Commelina benghalensis, Portulaca oleracea…)

Characters of adaptation to cultural practices

Fertilization system generally self-compatible ( Commelina benghalensis has self-compatible aerial flowers and cleistogamous underground flowers).
Pollination by the wind or usual insects ( Poaceae, Asteraceae…)
High seed production in favourable conditions, but also possible (in a limited way) under conditions of stress.
A number of types of reproduction ( Cyperus rotundus, Imperata cylindrica seeds and rhizomes, Portulaca oleracea, Commelina benghalensis seed and cuttings)

Rapid growth at the seedling stage ( Rottboellia cochinchinensis)
High rate of photosynthesis
Rapid development of the root system
Rapid partitioning of photosyntates to new leaves
Rapid vegetative growth to rerach the reproduction stage ( Euphorbia heterophylla can produce seeds four weeks after germination)
Special "arms" for the competition :
- nitrophilia (species developing in places enriched by nitrogenous elements such as Amaranthus spinosus, Eleusine indica)
- spreading habit ( Commelina benghalensis)
- allelopathy ( Cucumis melo, Tithonia diversifolia)
Independence from environmental constraints
- Strong acclimatization capacity under variable conditions (phenotype and genotype plasticity)