By definition, a weed is any plant that crowds out cultivated plants. In nature, plants will only crowd out other plants when the environment is altered and one plant is deprived of some nutrient or gained by another. While we tend to think of forests as stationary ecosystems, they’re always moving. As we see in succession, when one layer of pioneer plants has amassed enough biomass to sustain a perennial herb layer, the grasses move in and “crowd out” the pioneers. As more biomass is generated at the top-soil layer by the bundled root-systems of the perennial grasses, the shrub layer encroaches followed by the shorter, then taller trees. With each step, we see a more complex ecosystem unfolding until the web of biodiversity is strong enough to sustain minor alterations.
“Weeds” or those plants we have labeled weeds, contribute to biomass, cultivation, offer a food source for beneficial insects and play a part in the development of the ecosystem. And in many cases, those plants we’ve labeled “weeds” are far more beneficial than the plants we’ve cultivated. Dandelions, for example, are completely edible, hold nutrients from the soil and redistribute these nutrients at the end of the life-cycle, are insectary, and offer humans some medicinal value. Grass, on the other hand, prevents erosion and provides biomass, but otherwise, isn’t very useful to humans, doesn’t attract beneficial insects and takes in more nutrients than it contributes.