Turning young weeds into the soil before they can mature and go to seed helps reduce the number of future weeds.
Every farm has weeds, and the last thing a busy hobby farmer needs to do is waste time. Managing weeds on a farm is a different ballgame than a nursery, but many of the weed-management tactics described below are effective across the board, no matter what type of property you've got. They're intended to be simple, cost-effective solutions to your worst weed woes, freeing up your time, money and energy for other, more fun farm chores.
What is a Weed?
Before we tackle weed-management techniques, we first need to define what makes a particular plant a weed. It's also important to understand why some weeds are worse (or better) than others. Tom Lanini, an extension weed ecologist at the University of California at Davis, says a weed is classically defined as a plant out of place.
“But to expand on that,” he adds, “I think a weed is a plant that causes economic or aesthetic loss.”
Economic loss could be in the form of reduced yield or the cost of managing the weed, and aesthetic loss is how the weed's presence impacts the overall visual appeal of your hobby farm. This is in the eye of the beholder, says Lanini. Every hobby farmer has his own level of tolerance for weeds in regard to the aesthetics of the farm, meaning that some people will find it necessary to control weeds more than others. Let your own tolerance be your guide, bringing weeds in check when you feel they are impacting your bottom line to an undesirable point.
Using Lanini's definition, when looking at a ditch alongside your driveway that's filled with grasses, field daisies, goldenrod and other plants, do you see a weed or a patch of wildflowers?
“Weeds provide a wide range of benefits or ‘ecosystem services,'” says Eric Gallandt, a weed ecologist with the University of Maine. In a situation like this, he says, “they protect the soil from erosion, cycle nutrients, [and] offer habitat and food for many organisms,” including thousands of species of predatory beneficial insects and pollinators. There are no crops growing in that ditch, so there's little to no economic loss, and the aesthetic issue could be a loss or a gain depending on your opinion of field daisies and goldenrod.
“Weeds can be good in some situations,” Lanini adds, even in your fields. “During the time that a crop is not being grown, they may act as a cover to help cycle nutrients, preventing them from being leached. Low-growing, shallow-rooted weeds in an orchard or vineyard are obviously not impacting yield and could help provide a firm surface during rainy periods.”
The point is to choose your weed battles carefully.
Proactive Weed Management
In many situations, the design and layout of your hobby farm's planting beds can determine how many weeds you'll have. Diverse gardens that contain a multitude of plant species are less likely to face weed woes. Monocultures, especially those with a lot of exposed bare ground between plants or crop rows, are welcome mats for weeds.
Planting gardens and fields with a variety of crops, each filling their own layer of the garden's canopy and thereby completing the garden like pieces of a jigsaw puzzle, leaves less room for weeds and reduces nature's tendency to fill the gaps with its own “weedy” biodiversity. Be as diverse as you can in your plantings, and choose easy-to-maintain native species whenever possible.
Anything applied to the soil surface with the intent of reducing weeds, cutting down on watering and stabilizing soil temperatures is considered mulch. Agronomist Preston Sullivan suggests using organic mulches, such as pine straw or cover-crop residue, to help control weeds. Applying 3 or 4 inches of these products, straw, shredded leaves, untreated grass clippings or compost around plants (but not directly on them) and between rows keeps weed seeds in the dark and prevents them from germinating.
Covering the soil with unwaxed corrugated cardboard or several sheets of newspaper before laying down the organic mulch takes weed prevention a step further and serves as season-long weed control. Plastic-film mulches are effective, too, though they'll be headed to the landfill after a season or two of use.
Biodegradable film and paper mulches are a terrific addition to the weed-fighting arsenal and are able to control weeds just as effectively as plastic films without the need for disposal. At season's end, they can be tilled into the soil. The films are made of a cornstarch-based material, and the paper versions are derived from recycled paper coated in a vegetable resin.
Fallow ground is prime real estate for weeds. Shield bare soil and out-of-rotation fields with a cover crop. Annual cover crops out-compete weeds and recycle nutrients back into the soil while holding it in place and preventing erosion. Low-growing perennial cover crops, like clover and alfalfa, become a living mulch if planted between rows during the growing season. They also serve as a nectar source for beneficial insects while luring pollinators and displacing weeds.
Lee Reich, PhD, a garden and orchard consultant and author of Weedless Gardening (Workman Publishing Company, 2001), notes, “Some cover crops, such as rye, oats and sorghum-sudangrass hybrids have an alleopathic effect; that is, they combat weeds by releasing natural weed-suppressing chemicals into the soil.” In his book, he mentions a study in which rye effectively reduced pigweed by 95 percent, ragweed by 43 percent and purslane by 100 percent. “The effect,” he says, “is only on small seeds,” making it possible to plant large seeds, such as corn, cucumbers and squash, directly in the field after the rye has been cut.
When irrigating the garden with overhead sprinklers, water is lost to runoff and evaporation, and more often than not, paths and margins are irrigated right along with the desired plants, causing weed seeds to germinate and weed seedlings to thrive. Installing a ground-level or below-ground drip-irrigation system targets water precisely to plant's roots, eliminating waste and discouraging weeds.
Managing the seed bank
The aim of this proactive measure is preempting weed-seed production in the hope of reducing the future weed population. Gallandt describes this approach as farmers mechanically or manually cultivating “early and intensively enough to give the crop a competitive size advantage and then letting the crop take care of itself. Yield will not suffer from later-emerging weeds, but many of these will mature and can produce considerable seed rain, thereby replenishing the weed population for next year,” he says. “An alternative to this management philosophy is to manage the weed-seed bank. This will require cultivation and hand weeding early in the season, as before, but with an additional focus on [the removal of seed heads] or growing short-season crops that mature before weeds go to seed. The aim is to preempt weed-seed production. Without seed rain, weed densities will be lower in subsequent crops, and weed management requires fewer cultivation passes and less hand weeding.”
A 1986 study reported in the journal Weed Science noted that by simply not tilling a tobacco field, farmers saw a 68-percent reduction of weedy grass species and 71-percent reduction of broad-leaf weeds. Tilling brings weed seeds buried beneath the soil to the surface, where they are exposed to light and can germinate. No-till methods do not disturb the soil through cultivation.
Conventional no-till farming often involves the application of chemical herbicides to kill existing weeds; seeds are then planted through the weed residues. Organic farmers and gardeners can either use organic herbicides in the same manner or top-dress planting beds with regular additions of organic matter, causing a layered, mulching effect and encouraging the resident soil life to thrive undisturbed. Both Gallandt and Sullivan remind us, though, that no-till methods tend to shift weed troubles away from annual weeds and toward perennials, which, unfortunately, may be more difficult to control in particular areas.
Reactive Weed Management
Mulching around crops cuts down on watering needs and reduces weeds.
Investing in a good hand weeder (my favorite is a Japanese tool called a hori-hori) is a smart idea if you plan to do a lot of hand weeding. Although time-consuming, hand pulling is the perfect choice for smaller gardens and areas where other techniques are not appropriate or possible.
Be sure to weed after rain or irrigation to ensure soft soil and aid in the removal of the entire weed. Leaving root pieces behind often ensures the weed's return.
Tilling and cultivation
Turning young weed seedlings into the soil, either by hand cultivation with a hoe or by mechanical tilling, is great for reducing the number of weeds that reach maturity. It's one of the oldest means of weed control—after hand-pulling, of course. Cultivating or tilling established perennial weeds is seldom a good idea, though, as the process chops up the roots and propagates them. (Weeds like Canadian thistle, quack grass, knotweed and field bindweed are notorious for this.)
Cultivation works best after a process called pre-germination. Gallant suggests an initial shallow cultivation to promote germination of weed seeds followed by another cultivation to kill the resulting seedlings, noting that this process can “dramatically reduce the population of annual grasses, such as yellow foxtail or crabgrass, within the year.”
Portable propane-fueled weed torches, commonly known as flamers, fry weeds in a single pass. “Flaming is very effective on small weeds, in particular,” Lanini notes. “It is better on broad-leaf weeds, which have growing points at the top of the plant, and much less effective on grasses, where the growing point is below the soil surface and protected from the heat. In general, you do not need to turn a weed into charcoal to kill it but to only heat the tissue sufficiently to break the membranes of the plant cells. I can't stress [targeting] little weeds enough when using flamers. Large weeds require a lot more fuel to kill and are more likely to recover if all the tissue is not killed.”
Flamers can be used instead of cultivation and tillage after pre-germination, too, killing the resulting weed seedlings with heat rather than disturbance—a great technique for no-till, organic farmers.
White Chinese geese are very active and energetic foragers and are primarily vegetarians; other useful weeders include Emden geese and Toulouse geese. Because they prefer grasses to broad-leaf plants, weeder geese are terrific at controlling grassy weeds in strawberries, raspberries, corn and other crops, as well as in fruit and nut orchards. Young goslings are pastured in the field when they are 6 weeks old and are guided through the fields by strategic placement of drinking-water troughs.
You'll need to provide shelter at night to protect the geese from predators and remove them from fields before the fruit begins to ripen. Do not allow weeder geese to forage where fertilizers, herbicides or insecticides were recently applied, and be sure to provide them with pelleted feed in the evening to ensure a balanced diet.
The Department of Animal Sciences at the University of Missouri-Columbia recommends using two to four geese per acre. At the end of the season, the geese can be overwintered inside a coop or other shelter and released into the field again the following spring, making them useful weeders for several seasons.
Although they should remain toward the bottom of your list of reactive weed-management tools, herbicides are a valuable weapon against weeds. Turning to chemical herbicides is a personal decision for hobby farmers and one not to be taken lightly. If you choose to use them, follow all label instructions, including safety measures and application rates.
Many organic herbicide alternatives on today's market are effective against common weeds—annual species, in particular. Lanini agrees.
“I like Weed Pharm (acetic acid) and GreenMatch (d-limonene). They have been relatively effective under a wide range of conditions,” he says. “When I direct-seed a crop, particularly one that is slow to emerge (i.e., bell peppers), I like to wait until I see the very first pepper seedling emerging and then treat the entire area with an organic herbicide or propane flamer to kill all the weeds that have emerged ahead of the crop. (Of course, I also kill the first pepper seedling with this treatment.) Since I have not disturbed the soil, most weed seeds that were likely to emerge have already done so, and the remainder of the crop will grow under relatively weed-free conditions.”
There is no doubt that weeds are best controlled by employing a number of these techniques in combination. Find what works for your hobby farm by picking and choosing the weed-management techniques that work best for you.
About the Author: Jessica Walliser is a horticulturist and radio host in Pittsburgh, Pa. She is the author of several gardening books and a garden columnist with the Pittsburgh Tribune-Review. The weed du jour at her place is ground ivy—otherwise known as creeping Charlie. And creep it does.
This article originally appeared in the July/August 2011 issue of Hobby Farms.