Agriculture Reference
In-Depth Information
• Break up hardpans and compaction and control erosion.
• Increase the organic matter content of the soil as they continually grow and die.
• Tell us a tremendous amount about the nutritional condition of our soil through
their presence and growth habit.
• Fix nutritional imbalances, vastly improving soils in as little as a couple of years,
or sometimes decades or centuries. That's the role of weeds in nature.
• Provide homes and food for microbes and animals.
So why do weeds grow in the first place? Weeds are there because they are the most
suitable plant for the job, more suitable than what we're trying to grow. Most weeds grow
in very specific soil, nutrient and climate conditions. In fact, you can tell a lot about the
conditions of soil just by the weeds there. They are as useful as a soil nutrient test for dia-
gnosing certain fertility issues.
Of course, we don't really want weeds to be there because we're trying to grow
something else. To a certain extent, they can make a crop healthier, but they can also com-
pete with our plants for nutrients and water, especially if they get too big. The other main
reason for not wanting weeds — that they are “ugly” — is debatable when you think
about it, but understandable. At some point in our history, we started applying an aesthetic
order to our gardens that is reminiscent of the order inside our houses. I'm okay with that.
I prefer a weed-free bed, too.
So a weed is simply a plant growing in an inconvenient spot, working to fix our soil. It
can be clover growing in a lawn, or wildflowers growing in a corn field. In another
garden, they might be desirable plants. Weeds persist despite our efforts to get rid of them.
They're able to outcompete other vegetation when that vegetation is sick, growing in the
wrong spot or poor soil conditions. When fertility, soil texture and soil structure are
altered, the weed population will also change; and importantly, when these factors are im-
proved, the desirable plants will outcompete the weeds.
A plant of some kind will almost always grow where there's bare soil, because it has
the light and space needed for seeds to germinate. Good examples are thin or short turf,
shrub beds without ground cover and mulch, bare soil in vegetable beds, and gravel path-
ways. In fact, some weed seeds remain dormant and viable in the soil for decades, even
centuries, just waiting for the right conditions to germinate, and many weeds produce a lot
of seeds.
Another way that weeds can proliferate is through growth strategies. Some annual
weeds have several life cycles per year. For example, a plant like common chickweed or
pepper cress produces seeds, which germinate quickly, producing more seeds, and the
cycle continues. Many perennial weeds have deep and extensive root systems which
might regenerate several new plants when damaged. And many weeds, such as dandelions
and purslanes, can mature their seeds even after they have been pulled.
