Herbicides for Sunflowers

Sunflowers grow slowly when first planted, putting them at high risk of being overtaken by weeds. Weeds in a sunflower bed reduce the overall health and yield of sunflowers, so it is important to have good weed control during those first weeks when sunflowers are at their most vulnerable. After three weeks, sunflowers become vigorous competitors with weeds. Choose herbicides labeled for use with sunflowers.

Weed control options for sunflowers consist of both tilling and herbicides. If tilling is not an option, or if you prefer to use herbicides, several exist on the market that can give you good weed control for your sunflower beds at various stages of growth. However, not all herbicides are appropriate for sunflowers, as many herbicides not labeled for use with sunflowers can damage your crop.

The use of herbicides varies depending on soil type. Additionally, many pre-emergence herbicides, require rainfall or watering to attain maximum weed control results.

Pre-plant herbicides are applied before the actual planting of sunflower seeds. When applying herbicides before planting, you need to till the soil twice as deep as you are intending to plant sunflower seeds.

Examples of preplant herbicides include, Prowl 3.3 EC and Sonalan HFP by XX and Dual Magnum by XX, which controls the growth of annual grasses and well as nut sedge and other broad leaf weeds like pigweed, thistle, and bindweed. Before applying any herbicides, follow recommendations on the label of your chosen herbicide for dosage and any special instructions.

Preemergence herbicides are used after the planting of sunflower seeds, but before weed-seeds sprout. These kill weeds, giving space for the sunflowers to grow. For preemergence, Prowl 3.3 EC and Dual Magnum also work well for weed control and Spartan 4F is another option for preemergence.

However, it is important to apply these herbicides directly after planting as they can harm young sunflower shoots. If using Spartan 4F, apply directly on the soil surface for control of broad leaf weeds. It must be applied at planting time or within three days of planting otherwise it may cause injury to sunflower growth.

Postemergence herbicides can be applied after the sunflowers have started to grow. The best time to use these herbicides is when you have young weeds that are growing rapidly. Waiting until the weeds mature reduces the effect of the herbicides. Apply postemergence herbicides by ensuring effective spray coverage. Select 2 EC is a good herbicide to use for this and works to control different weed grasses and wild oats.

If you are growing Clearfield Sunflowers, Beyond works well postemergence; however, if used on other types of sunflowers, Beyond can be harmful.