The best weed control is prevention and the best prevention is keeping weed seeds out of the field. This is a difficult task. Most weeds produce between 5000 and 100,000 seeds per plant. By comparison, crops like grain or vegetable seed produce between 100 and 800 seeds per plant. Once weeds are allowed to go to seed the battle is on and some weed seeds can last many years. Unlike crop seed, weed seeds do not germinate all at the same time and some can remain viable for many years. The factors that break dormancy are interrelated and include environmental conditions, physiological conditions within the seed, soil characteristics and other factors. The number of years that it takes for dormant seed to die ranges from 2 years (sunflower) to 80 years (lambsquarters).In general, broadleaves are more persistent than grasses, small seeds are more persistent than large seeds and annuals are more persistent than perennials. Small seeds cannot germinate from deeper than 3 inches while larger seeds and perennials can emerge from 5 inches.

I’m getting rid of the weeds!

To contact Barry Tickes go to: btickes@ag.arizona.edu.

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.