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Tom Schwartz

Schwartz

When I was a boy growing up in central Wisconsin, my mother looked forward to the arrival of dandelions in early spring. Dandelions were food.

Every spring mom would send my sisters and me out to pick dandelion greens. We would eat them like spinach or mustard greens. They weren’t bad, although they became increasingly bitter as spring moved into summer.

Now, instead of eating dandelions, I fantasize about a dandelion-free lawn. I have found that that goal is achievable if you are willing to put in the effort required. Dandelion, Taraxacum officinale, also known as poofball or lion’s tooth, is a perennial weed that regularly invades residential lawns. It is a troublesome weed.

Dandelions pose a double threat. They produce a mass of small airborne seeds that are extremely opportunistic. They can find the smallest opening in the turf or bare soil and grow aggressively. At the same time, they send down a strong taproot which can extend ten inches or more. If the homeowner pulls up most of the dandelion plant, what remains is usually enough to send up a new plant.

Hand digging can be effective in controlling dandelions when used in conjunction with other measures. The problem for homeowners is that deep taproot that keeps dandelions tied to the ground. If you simply cut off the dandelion plant at root level, it will quickly grow back. Even if you pull up what you can of the taproot, what remains will often grow into a new plant.

I had the opportunity this week to ask Don Morishita about the effectiveness of hand digging dandelions. Don is a professor of weed science, University of Idaho Extension specialist and superintendent of the UI Kimberly Research and Extension Center. He grew up in Idaho Falls where his dad was also weed superintendent.

Don mentioned some of his earlier research in which dandelions were dug up at varying depths. The research showed that if part of the taproot is left in the ground within the top two inches of soil, it will most likely generate a new plant. However, if the top two inches of the taproot is removed, the likelihood of a new plant emerging drops significantly.

It is best to dig up dandelions after irrigation while the soil is still somewhat moist. Dig around the plant and remove at least the top two inches of the taproot.

According to Don, an integrated approach to dandelion control normally warrants the inclusion of chemicals. Herbicides work in two different ways. A pre-emergent herbicide prevents weeds from emerging as new seedlings. A post-emergent herbicide kills the plant.

There are also two different types of herbicide. A non-selective herbicide kills all plants. The most common ingredient in non-selective herbicides is glyphosate. The other type of herbicide is a selective broadleaf herbicide. It kills broadleaf plants without harming grasses.

Pre-emergent herbicides can be effective when applied at the right time (optimally two weeks before seeds start to germinate in the spring.) A pre-emergent must be used before seeds germinate. It has no value after seed germination.

According to the University of California Integrated Pest Management website, pre-emergent herbicides containing dithiopyr or isoxaben have been effective in managing dandelions.

Selective broadleaf herbicides are often called systemic herbicides because the plant moves or translocates the chemicals from the leaves to the roots, killing the plant.

Chemicals included in selective broadleaf herbicides include 2,4-D, dicamba, MCPA and others. According to the University of California two additional herbicides, carfentrazone and iron HEDTA, have shown promise for control of dandelion seedlings.

Remember that the best guard against broadleaf weeds (including dandelions) is healthy turfgrass. Keep your soil healthy through regular amendments of compost or topsoil. Aerate the lawn periodically and over-seed any bare spots to discourage weeds from homesteading.

Don Morishita also mentioned that research has shown that regular fertilization can play a part in dandelion control. Experiments involving different fertilization programs revealed that dandelions tended to thrive in over-fertilized and under-fertilized soil but did not thrive in appropriately fertilized soil.

Don suggested that the popular regimen of three or four applications of fertilizer during the growing season can help in suppressing dandelion populations.

Garden Wise is presented by the Magic Valley Master Gardener Association. We will try to answer questions of general interest submitted by the community. Please submit questions to gardenwise@cableone.net.

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Garden Wise is presented by the Magic Valley Master Gardener Association. We will try to answer questions of general interest submitted by the community. Please submit questions to gardenwise@cableone.net.

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