The best way to keep weeds out of the lawn is to never let them get started. Keeping turf thick and healthy using organic methods is the best defense. The other key is regular applications of pre-emergent and post-emergent herbicides. Here are the best organic choices in both categories.

Preemergent Weed Control

For pre-emergent control, the only organic solution is corn gluten meal, a common food additive that has been proven to prevent seed germination. Available as either a powder or granule, it can be applied to the lawn with a fertilizer spreader. One application works to suppress seed germination for four to six weeks. It works on all types of seeds and only on seeds. It does not harm existing plants.

Timing Is Crucial

Corn gluten can reduce lawn weeds by as much as 93 percent when used regularly over time, and should be applied when seeds are actively germinating in spring and fall, typically in February through March and again in September through October. The easiest way to tell when to apply it is to watch for the first dandelions. Don’t wait.

Post-Emergent Weed Control

Some weeds are bound to sneak through; then bring out a post-emergent product like 20 percent horticultural vinegar because nothing kills existing weeds faster. This non-selective acid works with sunlight to burn weeds back to the roots, so use it on a sunny day. At full strength, it works on all types of weeds. Increase its effectiveness by adding an ounce of orange oil to each gallon of 20 percent vinegar. Adding a drop or two of dishwashing liquid improves adherence. Spray the crown of each weed thoroughly and a few hours, they will be dead.

Pulverize Weed Killer for Lawns

Another effective organic post-emergent weed killer is called Pulverize. One advantage  over horticultural vinegar is that it works better in shaded areas and on cloudy days. Available in three progressively stronger formulas, the green “Weed Killer for Lawns” is available in a hose-end spray bottle, which allows users to quickly and easily spray the entire lawn instead of spraying individual weeds.

AgraLawn Crabgrass Killer

Crabgrass and other grassy weeds are difficult to kill without also harming the lawn. AgraLawn, a spot treatment solution made from cinnamon bark, acts fast and will not harm common lawns like St. Augustine and Bermuda, but the area to be treated must be wet for it to work. For best results, apply it during the morning while morning dew is present, or wet the affected area with a hose, irrigation or spray bottle.

Joyce Connelley is vice president of marketing for Marshall Grain Co., DFW’s leading organic garden center and landscape services company, located at 5311 Colleyville Blvd., in Colleyville. For more information, call 817-416-6600 or visit MarshallGrain.com/tips-and-techniques.