When do seeds germinate?

By Barry Tickes, UA Area Agriculture Agent

The length of time for weed seeds to germinate can vary considerably even within the same field due to variations in soil and microclimatic conditions. Every year can be different.

We conducted a test to determine how long it would take for various weed seeds to germinate after exposure to moisture. Seven summer and winter annual weeds, two grasses, and five broadleaf weeds were chosen for this test.

Seeds for the weeds were placed in teabags and buried one-quarter inch below the soil surface and in the seed row of newly planted lettuce fields prior to the germination irrigation. Teabags were pulled every 24 hours and evaluated for germination.

This procedure was repeated in sprinkler and furrow irrigated fields at eight locations in Roll, Bard, the Gila Valley, and the Yuma Valley. The tests began in August and were conducted each month until February.

The time to germination for the summer annual grass (barnyardgrass) was 24 hours in August and September, became longer in October (48 hours), and still longer in December (96 hours). It did not germinate in January.

The winter annual grass (cannarygrass) took 168 hours to germinate in September and dropped to 96 hours in December.

The summer annual broadleaves took from 24 hours (purslane) to 96 hours (pigweed and nightshade) to germinate.

The winter annual broadleaf weeds (lambsquarters and Shepardspurse) took from 72 to 168 hours to germinate.

Contact Tickes: (928) 580-9902 or btickes@ag.arizona.edu.

The use of pelargonic acid as a herbicide

The Vegetable IPM Team asked Barry Tickes what is one of oldest acids used as a non-selective herbicide. His answer is in the following video: