Natural Weed Controls
If you are using strong enough solutions of homemade weed killer to actually kill weeds, you are probably doing damage to the soil and surrounding plants.
It is important to understand that homemade remedies are not especially effective and do not kill weeds. With that said, there are some great strategies that can be combined with natural weed "CONTROLS", and with repeated applications of standard solutions you can keep weeds weakened, small, and minimize spreading. I can be satisfied with that. Especially when you consider that lawn safe selective weed killers are not a one application solution either, and Roundup kills everything and is not safe in the soil.
Pulling weeds by hand is probably the most effective thing you can do to reduce weeds. After the soil gets a good rain soaking is the best time for efficient pulling, but wait til it is not mushy walking out there. The roots can usually be teased out well when the ground is soft and loose. Loosen around the weed with a weed fork. For many weeds it is important to get the whole root or you have simply multiplied the number of plants that will grow from each bit of root left behind.
Mulching: A thick layer of mulch can prevent weed seeds from germinating and smother less aggressive weeds. To increase the effectiveness of mulch I first lay down several layers of newspaper, which will eventually breakdown. Water permeable weed barrier can also be used but is best used for "permanent" plantings of shrubs and trees rather than perennial beds. Aggressive weeds still often find their way through barriers and of course weed seeds will fall or blow to the surface and germinate.
Tilling: Reduce or minimize tilling and digging to avoid churning up weeds seeds from deep in the soil. No till gardening leaves your soil structure and beneficial organisms undisturbed.
Intensive Planting: Tightly spacing plants will "crowd" out undesirable weeds and plants. By limiting space and sun seeds will not germinate and thrive once your plants have matured.
Solarize: To eliminate weeds over a large area, lay down a heavy clear plastic sheet/tarp in the heat of summer to trap heat. It will get hot enough under the tarp to kill weeds over about 4 to 6 weeks. Remove the tarp once everything has turned brown and dry. Once removed, weed seeds turned up in digging or tilling will often still be viable. You may want to till, allow seeds to germinate and re-solarize.
Proper Lawn Care: To minimize weeds in your lawn, take proper care of the grass. Keep the grass long to shade the soil. Water infrequently but deeply. Fertilize in low doses to maintain good health without encouraging fast growth. If your lawn is healthy and thick weeds will have a much harder time establishing.
HOMEMADE WEED CONTROLS
Boiling water can be somewhat effective for less aggressive weeds. Target your pour directly on a weed by using a tea kettle. Or open a can on both ends, push into the soil over the weed, and pour into the can so as not to damage surrounding plants or grass. Add salt to the water to make it more effective.
Household vinegar works well for newly sprouted weeds. A little dish detergent or vegetable oil added to the spray bottle will help the vinegar adhere to the foliage surface. For aggressive and established weeds you can find a stronger vinegar, 20 percent acetic acid vinegar solution, at garden supply stores. Repeated applications are necessary as acids are a desiccant (draws the moisture out of the plant) and the roots will try hard to deliver more moisture. Vinegar of course will harm any plant it is applied to. But it does break down easily in water and generally will dissipate without harming the soil. Microorganisms that are important to your soil however may be harmed.
Rock salt or table salt at the base of the plant can help knock down weeds. A little salt added to boiling water, vinegar, and other home remedies can make a solution more effective. Do apply targeted and sparingly, as excessive salt can damage soil and render soil uninhabitable for any plant. And salt does not dissipate, it just leaches to other plant roots and into our water sources. Salt can also erode concrete over time.
Borax is a naturally occurring substance that can be used instead of salt. It is very potent and will still harm the soil.
Dish soap on its' own will not knock down weeds, but is a surfactant. It helps to spread the active ingredient over the foliage and may enhance absorption as well as break down waxy surfaces on leaves.
The natural acid of lemon juice can be sprayed on weeds to dry them out. Combine with vinegar for a more effective solution.
Rubbing alcohol or vodka will dry out the plant. Works best sprayed on weeds in sunny areas.
Corn gluten (granules, pellets or powder left from milling corn) has long been used as a pre-emergent. It will prevent seeds from sprouting. Look for certified organic at your local garden center or feed store and follow application directions. Do no over apply.
Retail Organic Herbicides
Several natural ingredient combinations are available commercially, so choose according to the weeds you are dealing with.
COMBINATIONS TO TRY:
1 gallon white vinegar, 1 cup salt, 1 tablespoon liquid dish soap. Spray on weeds on a hot sunny day for best results.
2 ounces rubbing alcohol or vodka, 2 cups water, 2 drops liquid dish soap. Spray on weeds on hot sunny day for best results.
1 gallon 5% white household vinegar, 1 cup salt. Use 20-30% vinegar for a more effective solution, but use gloves and goggles to avoid possible burns.
Equal parts vinegar, salt and dish soap.
Be patient with these natural solutions, you will not see immediate results. Be persistent with multiple regular applications and be satisfied with simply minimizing weeds rather than eradicating them.