Excluding Weed Seed from Containers

Weed management often suffers when there is a labor shortage. Good cultural and sanitation practices will reduce the number of weed seeds infesting containers and increase herbicide effectiveness in preventing weed germination and development.

The goal of a successful weed management program is to prevent weeds from germinating and competing with the crop by using a combination of cultural and chemical control tactics within an integrated management approach.

Weed free growing areas can be created with a good drainage system, gravel, concrete, weed-barrier (geotextile) or other organic or inorganic mulch. Exclude weeds by using weed-free growing substrates and preventing establishment of seeds carried by wind, irrigation water, equipment and tools. Cover stored substrate materials to prevent weed contamination. Substrates harboring weed seeds may be treated with heat or chemicals before use. Install and maintain filters or treat recycled and surface irrigation water to eliminate seeds. Clean plant debris and spilled potting-mix and avoid excess irrigation and standing water. All of these create habitat and favorable conditions for many weed species. Some weeds can germinate and grow in container drainage holes and directly compete with the plant for water and nutrients.

Maintaining weed-free non-crop areas is probably the easiest and the most effective sanitary practice for reducing weed seed numbers in your containers. Many weeds can project seeds over a large area (bittercress and oxalis); it is important to keep these plants from establishing in and around growing beds. Regular mowing of roadways, drainage ditches, areas between nursery beds, etc., will drastically reduce weed seed number and improve weed control.

Herbicides provide an effective means of managing weed in hard to mow locations. Post-emergence herbicides can be used to eliminate existing weeds and pre-emergence herbicides used to prevent weed germination and re-growth. Water quality and quantity may affect herbicide effectiveness. High water pH and dissolved organic compounds may reduce herbicide performance. Avoid herbicide leaching and runoff by limiting irrigation water after herbicide applications. Always read and follow directions on pesticide labels.