No one pays much attention to weeds, except to get rid of them. Yet in nature's scheme of things many are very useful and serve particular functions. Adaptability to all types and conditions of soil contributes to their successful growth. Take horseweed, for example, which under highly favorable conditions can grow up to 10 feet tall. These pesky plants will grow in hard, dry soil where most other plants will not grow.
Other species of weeds can survive in concrete, breaking out in small crevices.
One of the things that make weeds so successful is the number of seeds they put out.This is in marked contrast to the pampered cultivated plants. Pigweed can yield up to a million or more seeds per plant. The seeds also have a remarkable facility for survival.They can float about in the slightest breeze, attach themselves to clothing and other plants, and get carried all over the garden without the gardener's being aware of it.
Chopping up a plant can simply multiply it, since weeds can reproduce themselves from dry pieces of stem and stock. But do not overlook the advantage of this habit.
Weeds are often an indicator of the soil. Vigorous growth of ragweed and mayweed is usually found on fertile soil and tells the farmer it is suitable for crops. Sandbur and poverty grass denote sterile or poor soil, while an abudance of sheep sorrel points to an extremely acid condition that needs the corrective influence of lime.
The controlled use of weeds as companions to certain crops is well known to many organic farmers. The deep-rooting ones help bring back eroded and hard-packed soils. Pigweed, for example, brings up nutrients from deep soil layers. Many gardeners consider pigweed of particular value to potatoes.
You may go along with the idea that a weed is a plant out of place, or with Emerson, who said: "A weed is a plant whose virtues have not yet been discovered." Of course, weeds should never be allowed to dominate the food plants but, grown near many, they provide valuable companion crops. Lamb's quarter and thistle bring up minerals from the lower soil through their stalks and leaves.
Another interesting thing about weeds is that they seem to accumulate the nutrients in which a particular soil is deficient. Such weeds as sheep sorrel and plantain, which thrive best in acid soil, are rich in alkalinizing minerals, such as calcium and magnesium. Bracken, which grows best in phosphorous-poor soil, is high in phosphorous. Turning these weeds under instead of pulling them out will release their minerals into the topsoil, making them available to the roots of shallow food plants.
All weeds benefit the soil by conditioning it. Their extensive root systems leave fibrous organic matter that decays, adding humus to both. Another benefit is that they leave channels for drainage and aeration.
Learning to read weeds can be useful to the gardener. Weeds that indicate a crust formation or hardpan are pentcress, morning glory, horse nettle, field mustard, camomile, quack grass, and pineapple weed.
Weeds most likely to occur on cultivated land are chickweed, buttercup, dandelion, lamb's quarter, plantain, and common horehound. Sandy soils may have yellow toad, broom brush, aster, and most goldenrods. On alkaline soils we are apt to find sagebrush and woody aster, while limestone soils grow peppergrass, mustard, and wormseed.
If a plot of land grows healthy weeds it will probably grow good food crops as well. The rule of thumb is to let the weeds reach their full growth but cut them before they go to seed.Let them wilt a few days on the ground and then plow them under for green manure.
Weeds are not our enemies. With good management they can become our friends and co-workers.