Weeds affect us all. Older gardeners will leave a property that they love because they no longer can keep up with the weeds. Newer gardeners can get discouraged because weeds can take the fun out of gardening. And all of us regret the time that we must spend dealing with weeds.
Besides taking up valuable space, they compete with other plants for nutrients, water and light. Vegetables have reduced yields or do not produce at all under weedy conditions. A weedy garden is also unattractive.
In the past, 2, 4 D and similar selective herbicides were used to control broad-leafed weeds. Glyphosate weed killers were also used in home gardens to totally remove all plants from a specific area. In recent years these have lost favour and have been banned by many communities including Peterborough. Blanket or preventive approaches, besides raising health and environmental concerns, often fail and sometimes cause unwanted side effects or require constant application.
All weeds, whether they are perennial or annual should be prevented from going to seed and the seeds should be kept from germinating. A single crabgrass plant can produce 250,000 seeds in a season. Weed seeds in large numbers are already present in all soils and they remain viable for many years. For example, lamb's quarters seeds from under medieval ruins in Europe were found to be still viable after centuries.
Most weed seeds lie in wait for signals that the competing plants have been removed from above them and that there exists the right conditions for their germination and survival. They wait for one or various combinations of light, warmth, fluctuating temperatures, moisture or increases in nitrates and other chemicals that are found in disturbed soils.
Deep spring tillage, besides being hard on the structure of the soil, is just about the perfect source of these signals. For some vegetable gardens, and for some weeds, it makes sense to dig the garden, allowing the weed seeds in the top layer to germinate, and a week or two later, take shuffle hoe to the whole garden. This will kill most of the tender young weed seedlings, but not bring up many more new seeds.
The more you know about a particular weed and its life cycle, the easier that you can develop an effective strategy to combat it.
Perennial weeds need to be managed differently than annual weeds. Biennial weeds such as Queen- Anne's-lace, form roots and a rosette of leaves the first year and set seed the second.
The most effective way of controlling perennial weeds without the use of chemicals is to physically remove them or to discourage them through cultural practices. In many cases, all pieces of the underground roots and rhizomes need to be removed, particularly storage parts of the plants. Even if you cannot get the entire plant, repeated removal of leaves and stems, weakens weeds and eventually they give up. Examples of perennial weeds are dandelion, plantain, thistle, ground-ivy, quackgrass, and creeping bellflower.
Annuals should also be handpicked or killed by shallow hoeing at the seedling stage, but can be effectively controlled by preventing the spread and germination of seeds. Examples of annuals are crabgrass, barnyard grass, ragweed, wild buckwheat, smartweed, foxtail, lamb's quarters, purslane, pigweed, wild oats, and wild mustard.
Winter annuals can also germinate in the fall and flower the following year. Examples of these are henbit, shepherd's purse, and chickweed.
The objective is to get as much of the plant as possible including all of the roots. It is best to grab the plant close to the ground, encircling its leaves with the fingers of one hand. A small-bladed knife, an English-style weeding fork or sharp-edged hand trowel in your other hand can be used in the soil to slide under the roots of the weed to loosen them helping to remove the plant. This works best when the soil is moist and crumbly. If you disturbing the surrounding soil, mulch, or leaf litter, you run the risk of bringing deeply buried weed seeds closer to the surface. Mixing uncomposed mulch with the soil also robs it of nitrogen. Hand pulled weeds can be left on the ground to break down except for any that have developing or mature seeds. Seeds should be cut from the plants and bagged for curbside disposal. Perennial weeds might stay alive in the home compost, but you can put them in the sun in a closed plastic bag for a month to finish them off.
Topdressing perennial beds with at least an inch or two of well-finished weed-free compost or leaf mulch reduces the number of weeds. This layer should not be dug into the bed. Instead, it should be left on top to act as a blanket blocking the light and reducing the temperature of the underlying layer. Compost is available from the City of Peterborough Waste Program. This finished compost is free of seeds, which is not often true for home compost. Smaller quantities are available at the Ecology Park. Compacted or poor soils favour many weed species. Yearly applications of compost contribute to the overall health of the soil and adding organic material alters soil structure of both sandy soils and clay soils. Aeration is improved with increased pore spaces allowing air to reach the root zone and the soil's ability to retain water increases with the addition of compost. A healthy soil often is all it takes to tip the balance in favour of your plants.
Try to relax. A few weeds won't destroy your garden and some weeds are necessary. Good luck, and may the fork be with you!