ANR-322, Revised Sept 1998. John W. Everest,Extension Weed Scientist, Professor, Agronomy and Soils, and Mary Beth Musgrove, Extension Program Associate, Horticulture, both at Auburn University

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Weed Control in Home Gardens

Good weed control may determine to a large extent the success of your home garden. Weeds compete with the crop for soil moisture, sunlight, space, and plant nutrients. They compound disease problems and serve as hiding places for insects. Also, weeds may prevent dusts and sprays from thoroughly covering your garden plants, resulting in poor pest control.

Weeds can usually be divided into two groups--grasses and broadleaf weeds. Grasses are multistemmed plants with fibrous root systems. Once grasses become established, they are difficult to control without injuring the vegetable crops. Grasses are very competitive in gardens and make harvesting difficult. Many broadleaf weeds grow upright and have taproot systems which make them easier to pull than grasses; therefore, the vegetables receive less injury.

Preventive Weed Control. New weed seed may be brought into a garden on plows or tillers that have been used in weedy areas. Compost and manures sometimes contain troublesome weed seed. Weedy hay used for mulch may bring an number of new weed problems. Occasionally, home-saved vegetable seed may also include some weed seed.

Most of the weed problems in the garden are homegrown problems. That is, they come from weed seed produced in the garden in years past. Season-long weed control to prevent weeds from reseeding should be a basic part of any weed control program. Controlling weeds by preventing them from making a seed crop may be a long-term process, but in the end it is the only sure way to control this problem.

Mechanical Weed Control. Historically, gardeners have used hoeing, plowing, hand-pulling, and mulching to control weeds. Mechanical control methods used on a regular and continual basis provide good weed control for serious gardeners. This usually means frequent light cultivations with a tiller or hoe to destroy weeds in the two- to four-leaf stage. A few minutes spent destroying the flush of weeds that usually emerge after every rain is much more effective than hours or days spent trying to destroy established weeds.

Many gardeners have too large a garden to control weeds in the time available for that task. A few well-managed rows may produce greater yields of higher-quality vegetables than a larger area tended in a slipshod manner.

Mechanical weed control gives immediate results. There are no problems of uniform application, drift, and residues as with chemicals. Weeds may be controlled mechanically under a wide range of soil moisture conditions, and very little skill is required. Also, mechanical methods may be used as often as needed. Mechanical weed control is the most practical approach to weed control in small gardens. The greatest weakness of mechanical methods is the lack of residual control.

Mulching. Mulch can be a valuable asset in controlling weeds in perennial and long-season crops like asparagus, strawberries, tomatoes, and peppers. Six inches of pine straw or 3 inches of leaves or well-decomposed sawdust will help suppress most weed problems. Mulch also helps keep the soil surface cool and cuts down the evaporation of soil moisture. Many gardeners clean-cultivate and mulch heavily to control weeds later in the season in crops like tomatoes, peppers, and okra because late cultivation could damage these large, spreading plants.

Mulch gradually decomposes during the season, and sometimes this may cause plants to develop a slightly yellow cast. A light application of about 1 pint of ammonium nitrate per 100 feet of row will usually correct this problem. Additional mulch may be added as needed when the older material settles or decomposes. At the end of the season, the mulch can be turned under or incorporated to add organic matter to the soil.

Chemical Weed Control. Most annual grasses are easily controlled with garden herbicides. However, herbicides control only small-seeded, annual broadleaf weeds that grow from the upper 1 to 2 inches of soil; they do not give acceptable control of large-seeded broadleaf weeds.

You can use a herbicide for grass control and then rely on hoeing, plowing, hand-pulling, and mulching to control weeds that escape the chemical treatment. It is not advisable to use a herbicide unless you are also going to control broadleaf weeds. Removing just the grasses would only remove some of the competition and would allow the broadleaf weeds to flourish. In a very short time, these weeds would replace the grasses and create an almost hopeless situation.

Seedbed Preparation. Chemical weed control will be improved by preparing the seedbed well. Destroy old crop residue, and turn it under early enough for it to decompose. Spread manure and apply lime and fertilizer as recommended by a soil test. A uniform, well-prepared seedbed will result in a quick crop stand and improved weed control.

Transplants. Herbicides listed in the table are intended for use before weeds begin to germinate and emerge. Chemicals used where transplants are to be set should be timed as directed on the label and applied to a weed-free seedbed. Weeds germinating before transplants become established should be removed before herbicides are applied.

Methods of Application. Read the label instructions before attempting to apply any chemicals. Cyclone seeders or spinner-type applicators are best for applying granular herbicides. Granules sold in shaker cans should be applied in two light applications going in different directions to get uniform application. Add liquid formulations to about one-half the required water before adding them to the sprayer tank. Make wettable powder herbicide formulations in a slurry in a bucket, and strain the slurry as you add it to the sprayer tank.

Residue Problems. Some herbicides may leave residues that could injure certain susceptible second crops. Avoid this by either selecting a tolerant second crop or by using a herbicide that does not leave a harmful residue. For example, fall vegetables should not be planted where atrazine has been used on corn. Dacthal may be used on turnips and squash, and these crops could be followed with snap beans or southern peas without any problems.

Equipment. Estimating or pacing off areas to be treated with a herbicide may lead to serious errors in application rates. You need a 50- to 100-foot tape to get accurate measurements. Use flags or stake markers to identify the area measured for treatment.

The bucket or sack-type cyclone seeders and spinner-type lawn fertilizer spreaders are very satisfactory for applying granular herbicides. Many models have a calibration sheet that can be used to calibrate the spreader for applying herbicide granules.

Pressure sprayers in 1-, 2-, and 3-gallon sizes are usually used to apply liquid and wettable powder herbicides. The 2-gallon size is the most popular except for with growers who have very large gardens. These sprayers are available with plastic, stainless steel, and galvanized metal tanks. The galvanized models cost less but have a relatively short life before rusting out. The more expensive stainless steel models should last indefinitely.

Application Suggestions. Use a tape measure to determine the number of square feet to be sprayed. Consult the table for the rate of application. Accurate measurements, correct weights, and uniform application are essential for good weed control without injuring the vegetables.

Apply liquid concentrate and wettable powder herbicides in about 2 gallons of water per 1,000 square feet, using a compressed air sprayer. Application errors are not a serious problem for sprays at this dilution rate; however, they often become much more serious as the chemical concentration is increased. For this reason, it is not advisable to reduce the water rate. If the water rate must be adjusted, it would be better to increase it and spray the area twice, going in different directions.

Liquid or wettable powders must be agitated to prevent them from settling to the bottom. Periodically shake the sprayer tank while spraying.

Do not use a sprayer that has previously been used for applying 2,4-D or a similar herbicide. Immediately after use, take the nozzle apart, and clean the strainer, back flush the boom and hose, and thoroughly clean the tank before storing the sprayer.

Summary. Because of the high variability among vegetable crops, weed problems, cultural practices, and soil types, no step-by-step weed control system has been devised. Using a combination of herbicide treatment, mechanical weed control, and mulching--capitalizing on the best features of each of these practices--is the best approach to weed control in the home garden.

Precautions. Always follow the manufacturer's directions printed on the label for handling and use. Store and discard containers properly.

Weed Control Chart for Home Gardens

Crop	Asparagus (established), Carrots, Cabbage (transplants), Broccoli (transplants) Brussels sprouts (transplants), Cauliflower (transplants), Celery (transplants), Collards, Kale, Mustard Turnips, Lima beans, Okra, Peppers (transplants), Irish potatoes (after transplanting), Snap beans, Southern peas, Tomatoes (transplants) , English peas				Broccoli, Brussels sprouts, Cabbage, Cantaloupes (seeded) at 4- to 5-true-leaf stage, Cauliflower, Collards, Cucumbers (seeded) at 4- to 5-true-leaf stage, Eggplants (4 to 6 weeks after transplanting), Garlic, Honeydew melons (seeded) at 4- to 5-true-leaf stage, Kale, Mustard greens, Onions, Peppers (4 to 6 weeks after transplanting), Potatoes, Radishes, Snap beans, Southern peas, Squash (seeded) at 4- to 5-true-leaf stage, Strawberries (new and established plantings), Sweet potatoes and yams (at transplanting), Tomatoes (4 to 6 weeks after transplanting), Turnips (greens and roots), Watermelons (seeded) at 4- to 5-true-leaf stage		Irish potatoes, Lima beans, Snap beans, Southern peas
Chemical Name	trifluralin	trifluralin	trifluralin	trifluralin	DCPA		pendimethalin
Trade Name	Treflan EC	Treflan 5% granules	EZE Garden Weed Preventer 1.75% granules	Greenview Preen 1.47% granules	Dacthal W-75 herbicide	Ortho Garden Weed Killer 5% granules	Prowl 3.3EC
Amount Per Broadcast Acre	Coarse and medium soils: 1 pt. Fine soils: 1-1/2 pt.	Coarse and medium soils: 10 lb. Fine soils: 15 lb.	Coarse soils: 29 lb. Medium soils: 43-1/2 lb. Fine soils: 58 lb.	Coarse soils: 2/3 lb. Medium soils: 1 lb. Fine soils: 1-1/3 lb.	Sand or sandy loam: 6 to 8 lb. Silt loam: 8 to 10 lb. Clay loam: 10 to 14 lb. Silt loam: 12 to 14 lb.	174-1/4 lb.	Coarse soils: 1.8 pt. Medium soils: 2.4 pt. Fine soils: 2.4 to 3.6 pt.
Amount Per 1,000 Square Feet	Coarse and medium soils: 3/4 T. Fine soils: 1-1/8 T.	Coarse and medium soils: 1/4 lb. Fine soils: 1/3 lb.	Coarse soils: 32-1/2 lb. Medium soils: 43-1/2 lb. Fine soils: 65-1/4 lb.	Coarse soils: 3/4 lb. Medium soils: 1 lb. Fine soils: 1-1/2 lb.	Sand or sandy loam: 4 to 6 T. Silt loam: 6 to 7 T. Clay loam: 7 to 10 T. Silt loam: 8 to 10 T.	4 lb.	Coarse soils: 4 t. Medium soils: 5 t. Fine soils: 5 to 6 t.
Time of Application	Apply to weed-free soil anytime from 6 weeks before planting up to planting. If bedded culture is used, apply after beds are formed.				Apply to weed-free soil immediately after seeding appropriate crop. Apply directly over appropriate transplant crops after specified waiting period or growth stage. If weeds have emerged, soil should be clean-cultivated as needed before application.		For beans and peas, apply prior to planting, and incorporate. For potatoes, apply after planting but before potato emergence, and incorporate or irrigate.
Application Method and Precautions	Trifluralin must be thoroughly incorporated into the soil to a depth of 1 to 1-1/2 inches. To achieve this depth, set the incorporating equipment to cut 2 to 3 inches deep. Incorporate immediately after application for best results. However, incorporation may be delayed up to 8 hours after application.				DCPA will not control established weeds: it kills them as they germinate. If no rain falls within 3 to 4 days after application, irrigate with 1/2 to 3/4 inch of water to activate the chemical. If areas cannot be irrigated, lightly incorporate chemical into top inch of soil.		For best results, Prowl must be incorporated into the top 1 to 2 inches of soil by mechanical methods or by irrigation within 7 days of application.
Available Quantity	1 qt. container. Two-year shelf life if kept sealed and not allowed to freeze.	40 lb. bag. Good shelf life if kept sealed and dry.	1 and 5 lb. shaker cans. Good shelf life if kept sealed and dry.	5 lb. bag	4 lb. bag. Good shelf life if kept dry.	1-1/2 lb. shaker cans. Good shelf life if kept dry.	1 and 2-1/2 gal. containers. Two-year shelf life if kept sealed and not allowed to freeze.
Weeds Controlled	Grasses	Crabgrass, Goosegrass, Fall panicum, Foxtails, Barnyardgrass, Signalgrass, Seedling johnsongrass, Sandbur, Texas panicum, Annual bluegrass, Bromegrass, Junglerice, Stinkgrass			Crabgrass, Lovegrass, Witchgrass, Foxtails		Crabgrass, Goosegrass, Signalgrass, Sandbur, Seedling johnsongrass
	Broadleaf Weeds	Carpetweed, Chickweed, Florida pusley, Lambsquarter, Pigweed, Knotweed, Purslane, Henbit			Lambsquarter, Carpetgrass, Purslane, Florida pusley, Chickweed, Pigweed, Dodder		Chickweed, Florida pusley, Pigweed, Purslane, Carpetweed

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.

For more information, contact your county Extension office. Look in your telephone directory under your county's name to find the number.