Mankind’s struggle with weeds is almost as old as life on earth. Since the very first man, almost all of those who have been involved in producing food have had to do something about unwanted native plants. For most of the earth’s history, this has involved strenuous manual labor in one form or another—manually chopping, slicing, digging, or guiding an animal-drawn tillage tool.
Only in the last sixty to seventy years have there been other means and tools to combat unwanted vegetation. Half a century ago, struggling, sweating farmers welcomed the arrival of chemical herbicides. More recently it is becoming apparent that damage from overuse of herbicides can occur. While I believe that herbicides can have a place in broadacre farming of certain crops, for small-scale gardeners and produce growers, they may be more problematic than they are worth.
Herbicides basically fall into three categories. Some work by chelating the minerals needed for plant health, resulting in the plant dying from disease. The most common and widely used of this type is glyphosate, commonly known as Roundup. This class of herbicides creates long-term problems in the soil if overused. Another type of herbicide works as a hormone disrupter; an example is 2, 4-D. Herbicides of this type are quite toxic to handle and problematic around produce crops. Crops such as tomatoes can be damaged by 2, 4-D or similar herbicides used hundreds of feet away. The third type actually chemically burns the foliage; an example is paraquat, commonly known by the trade name Gramoxone. This type is actually the safest for the soil but is extremely dangerous to handle. You certainly wouldn’t want to apply it with a hand sprayer.
So if we choose to not use herbicides in our produce patch, what are our options? Many produce growers and large-scale gardeners are benefiting from plastic mulch. The most recent version of this is even better; biodegradable plastic mulch eliminates the tedious chore of removing it at the season’s end. This product is more expensive and probably unnecessary for small-scale gardens, but larger growers will find it very cost effective. The black plastic mulch is particularly valuable in cooler northern areas, since it helps to warm the soil in the spring. In southern areas, organic material mulch such as grass clippings or straw may be better.
Be cautious about covering a small garden with one large piece of black plastic and then planting through small holes. While this may work at times with some soil types and provide excellent weed control, it can also lead to oxygen depletion and waterlogging in the soil under the plastic. A better solution is the typical 3-to-4-foot-wide (1 m) plastic, covering slightly raised beds. Keep the planting holes in the plastic as small as possible for maximum weed control. In between the beds, we have several options for weed control—tillage, organic mulch, or living cover crop. Tillage or herbicides are most common on large operations, but there is a significant negative associated with this practice. Any time soil is bare and exposed, it is likely to be losing organic matter and biological life. A much better practice is covering the area between the plastic with straw or another organic mulch. The downside to this is it’s a lot of work unless you have specialized equipment, and the mulch can be difficult to walk through when harvesting.
My personal favorite mulch system is a living cover crop between plastic-covered beds. The cover crop can be a variety of plants, depending on the crop grown on plastic. If we are growing vining crops that will grow off the plastic, then it is necessary to restrict the cover crop to low-growing clovers and dwarf grasses. If the crop is upright, such as tomatoes or peppers, then we can use much more variety in the cover and mow if growth gets inconveniently tall. I tend to avoid perennial ryegrass or other hard-to-kill cover crops. Although they make a nice sod cover, they require too much tillage to incorporate at the season’s end. My preference is often white clover for spreading crops, and winter varieties of small grain thickly planted in the spring can work well for non-spreading crops. One technique to help make this successful is to lay all the plastic as soon as the ground is fit in the spring and get the cover crop established before the heat and drought of summer. Crops can then be planted at any time on the plastic strip, and the cover crop between the rows can be mowed if needed.
Not all crops are suitable for plastic mulch. Some that like cooler conditions will do much better with organic material mulches. There are many types of mulch that fit in this category—straw, grass clippings, leaves, newspaper, wood chips, and more. A good way to enhance the weed control and stretch other mulches is to put down a layer of newspaper or cardboard first. If it is breezy, you might find it easier to wet the newspapers in a tub before laying. The moisture will keep them in place until you can cover a section with another mulch. Avoid using wood chips in an area that you will later till. Too much woody material tilled into the soil will rob it of all the available nitrogen until the wood decomposes. Wood chips can be excellent mulch around perennial trees and bushes, but don’t pile it too deep. More than 3-4 inches (8-10 cm) can damage some plants. Avoid wood chips from walnut trees; they can harm other plants. Avoid fine sawdust. A small amount can go into a compost pile with food scraps, but as mulch, it is likely to cause anaerobic conditions.
Finally, old-fashioned tillage is still a viable means of weed control and is often necessary, particularly in small seeded crops such as carrots or early cool season crops like peas. Broadacre crops like corn and soybeans also fall into this category. I recommend planting crops that will be tilled or cultivated, close enough together that when mature, they will completely fill the row, shading out the weeds that would germinate later in the season.
Many gardeners plant all their crops in rows far enough apart to use a power tiller all season long. They would actually save labor and benefit their soil by planting many crops in beds and hand cultivating between narrow rows. This is one place that spending a little more on high quality tools is definitely worth it. A good quality hoe kept sharp will get a lot more done with less effort than will a cheap discount store tool. A midsize or larger garden will also find a wheel hoe very handy. The modern small-wheel models are easier to use than the old, high-wheeled ones that you may find at an old homestead.
Three final tips for tillage:
- Till before you think necessary; the smaller the weeds, the easier the job.
- Till as little area as possible. Don’t space plants farther apart than they need. (Of course, don’t crowd them either.)
- Till as shallow as possible to get the job done. The goal is to slice the weeds off just under the surface. Some weeds will still grow from their roots but will eventually die if never allowed to grow significantly.