The same question has come up several times in the last week: What is the best way to manage weeds in my garden?
I guess the appearance of the first crop of winter-rain driven weeds in our gardens area has something to do with this!
Where do they come from, and why are they so tough?
Weeds, unlike the veggies and flowers we plant, have grown forever without any help from man; they are survivors. Our crops, on the other hand, are selected for food qualities, not survival.
Weeds come from everywhere; wind, birds flying over, seeds or burrs stuck to your clothes; all are effective ways weeds spread their seed. Think of the soil as a ‘seed bank’. There are withdrawals (weeds germinated and killed, eaten by insects, dying from old age) and deposits (weeds going to seed, wind, etc.).
Weed seeds have what is referred to as ‘latency’ or waiting for the right conditions to germinate. Some seeds will germinate as soon as they hit the ground, others will wait, and some have specific requirements, including being burned, before they will germinate. What this means is that you will have weeds popping up, possibly for years. “A season with seeds is a decade of weeds”
Weeds hurt crop growth through competition for nutrients, water, and sunlight. The best weed control method is to prevent weeds from becoming well established in the first place.
The main ways we control weeds are cultivation (as with a hula-hoe), mulching, and hand weeding. Proper cultivation means scraping the soil surface (very shallow penetration of no more than 1/4″) with a hoe or other suitable tool to cut off and remove small weeds. Deep cultivation can prune crop roots, which can cause loss of yield. This concept is covered in the first few minutes of this video on Home Vegetable Gardening, Part 1 (it is at the very bottom of the page). Do book-mark and spend some time on this page as there is some GREAT information in the videos.
Mulching is an efficient means of weed control, and it also helps conserve soil moisture. Organic mulches, such as sawdust, wood chips, straw, lawn clippings, or other such materials, should be applied in a 2″ to 4″ deep layer on top of the soil. Organic mulches can be turned under periodically to help condition of the soil. Some of these materials (saw dust & wood chips) will require nitrogen when are turned into the soil. You can apply about 2 pounds of fertilizer per 100 square feet to make sure nitrogen is available to the mulch and crops. Fertilizing is not needed unless the mulch is turned into the soil, and less is required if the materials have rooted on the surface..
Weed-block fabric (aka ‘Garden Cloth’), newspapers, and other such materials can also serve as mulches. They serve the same functions as organic mulches, but they do not offer the soil conditioning potential of organic mulches. Black plastic can be placed on the soil immediately after the soil is prepared for planting. Transplants can then be set through the plastic by cutting holes just large enough for the plant to fit through.
My preferred method of controlling weeds uses deep layers of ground mulch over the planting beds. When plants are ready to put in the ground, I pull back the mulch, loosen the soil where I want to plant, make a hole and plant the seedlings in the ground. I try to pull a little soil up around the seed plug, and move the mulch back around the base of the plug. Ideally, the plant should not be far below the mulch, and the mulch should not actually touch the plants.
Weed management in vegetable crops – UC IPM
California Gardening, Vegetable page – UC CA Garden Info
Read the next article in this series: Building Healthy Garden Soil.