Keeping this in consideration, how do you control weeds in onions?
Herbicide application sequences in onion and garlic typically involve applying preemergence herbicides to control or slow the growth of weeds germinating shortly after planting, and applying postemergence herbicides during the 1- to 5-leaf stage to control any weeds that escape preemergence treatments.
Furthermore, can you use preen on onions?
Preen is safe to apply to the garden's soil before sowing some vegetables and transplants. Apply the product before sowing vegetable seeds and transplants such as peas, beans, tomatoes, peppers, eggplants, radish and onions.
Herbicides containing 2-4-D, dicamba, glyphosate or mecoprop are most effective on wild garlic and wild onions.