Husker Hort

A Nebraska View of Horticulture

The War on Weeds

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Dandelions

Dandelions

Spring has officially sprung. The crabapples and flowering pears are in full bloom. Tulips and daffodils are starting their flower show. Henbit and dandelions are looking gorgeous. Are the last two not quite the kinds of spring flowers you want in your landscape? If so, there are some things you can do. The key to knowing what to do when depends on the weed, but it all comes down to proper identification of the enemy and its life cycle.

Winter annual weeds bloom in the spring, produce seed, and die all before the temperatures get hot. One of the more common winter annual weeds is henbit. Henbit has scalloped leaves, a square stem, and little purple flowers at the tip of the stem. These weed seeds germinated last September or October. Henbit plants sat dormant throughout the winter just waiting for the right time to jump into flower and seed production. Post emergence, broadleaf weed, herbicides won’t do much good. Spraying might make you feel better, but it can cause the plant to produce and drop more seeds. If the area isn’t too large, these weeds can be hand-pulled. Increasing the density and health of the lawn in the thin areas can help too. Improve the lawn either by overseeding or by changing cultural practices to promote grass growth. If you choose to use preemergence herbicides, aim to apply in early September to control winter annual weeds. For the best selection of preemergence herbicides, consider purchasing them now and storing until fall.

Summer annual weeds germinate in the spring, grow throughout the summer months, and produce seeds and die before winter. One of the most common summer annual weeds is crabgrass. Crabgrass is an annual grass that often fills into areas where the turfgrass is thin. Crabgrass preventers, or preemergence herbicides, will help to keep seeds from germinating. These products aren’t effective for plants that are already growing, so they should be applied before the plants come up. Crabgrass needs a minimum soil temperature of 50 to 55 degrees to begin germination. Preemergence herbicides applied just prior to germination provide the longest period of control. If applied too early, some products are out of the soil profile before all of the weed seeds germinate. Now is the perfect time to apply the preemergence herbicides. Apply half the highest rate on the bag’s label now. A second application, again half the highest rate on the label, can be applied in 6-8 weeks to give extended weed control. Remember that these products need to be watered into the soil profile within 24 hours for best results.

Perennial weeds come back year after year. The common offenders include white clover and ground ivy, sometimes called creeping Charlie. Ground Ivy looks very similar to henbit, but the control methods are very different. Ground ivy also has scalloped leaves, a square stem, and purplish flowers, but the flowers are in the leaf axil, between the leaf and the stem, in comparison to henbit that flowers at the end of the stem. The best time to apply post emergence herbicides for perennial weeds is after a light frost in the fall with a combination herbicide that contains multiple active ingredients. These products will also work well to control other weeds like clover or dandelions in the lawn.

Positive identification is key to selecting the proper control method. With a little homework upfront, you can ensure that it is the daffodils and tulips you see rather than the dandelions and henbit in the landscape.

For more information contact Elizabeth Killinger at elizabeth.killinger@unl.edu, 308-385-5088, her blog at https://huskerhort.com/, HuskerHort on Facebook and Twitter, or visit the Nebraska Extension in Hall County website: hall.unl.edu.

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Author: Elizabeth Killinger

A Nebraska Extension Educator out of Hall County with a focus in horticulture and sustainable landscapes.

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