Dandelions in Montana Lawns: Timing and Control

Why are there so many dandelions in my lawn?

Because they reproduce two ways and thrive in gaps. MSU's 2025 weed post on dandelions says the two species most common in Montana are the common dandelion and the red-seeded dandelion, both from Eurasia. They are short-lived perennials that reproduce by seed and from their roots, tolerate a wide range of climates and soils, produce abundant seed and thrive in disturbed areas.

University of Minnesota Extension says dandelions grow a deep, branching taproot from 6 inches to 2 feet deep, that new plants can form from broken-off root sections, and that they thrive in thin lawns. MSU's conclusion is that large swaths of dandelions where turf used to be point to a problem beyond the dandelions themselves, usually thin, compacted or underfed turf.

When is the best time to kill dandelions in Montana?

Late summer and early fall. MSU says that is the best time because dandelions are moving resources from their leaves to their roots to prepare for winter, which carries systemic herbicides down to the roots and depletes root reserves for longer-lasting control. MSU adds that spring management, before flowering and seed production, can also be effective.

Regional research backs the fall timing. South Dakota State University Extension reports that its weed trials show fall timing has the best chance for excellent dandelion control. University of Nebraska-Lincoln turf specialists recommend September and October over spring for large or widespread infestations, for three reasons: herbicides move down to the root as the plant prepares for winter, there is less risk to non-target plants that have gone dormant, and the grass can fill the gaps left by dying weeds from late fall into spring.

Why do spring treatments disappoint?

Because they rarely reach the root. SDSU Extension summarizes a two-year Kansas study of spring applications: products containing 2,4-D applied before bloom (leaves present, no flowers) typically gave over 90 percent control 30 days later, while applications at peak bloom were inconsistent, sometimes above 90 percent and sometimes below 50. For every spring timing, control had dropped below 50 percent by November, even where it had been above 90 percent in spring.

SDSU's conclusion is that spring treatments mainly reduce seed production and improve looks, and should be followed by a fall application to fully control the weed. If you treat in spring, aim for the pre-bloom stage, when leaves are up but flowers have not opened.

Does digging dandelions actually work?

Yes, if you get the root. MSU says mechanical removal is very effective depending on the scale of the problem, that a taproot tool such as a dandelion fork makes it easier, and that pulling out as much of the root as possible gives the best control, since dandelions are less likely to regenerate from small root fragments. Digging is easier when the soil is moist, so the day after a deep watering is a good time to do it.

UMN adds that mowing dandelions before they seed reduces spread by seed but does not stop the existing plants from growing. On a lawn with a few dozen plants, digging in spring and again in late summer, combined with overseeding the holes, is a realistic chemical-free program.

Which herbicides does MSU mention for dandelions?

MSU names 2,4-D, dicamba and MCPP (commonly found in weed-and-feed products) as effective in lawns, and says spot-treating individual plants is usually more effective than broadcast application across large areas. Colorado State University Extension's fall weed control note lists products containing 2,4-D, MCPP, MCPA, triclopyr and clopyralid for fall control of dandelion, plantain, thistle and bindweed.

MSU also describes painting glyphosate onto a freshly cut dandelion to move it into the root. Glyphosate is non-selective and kills grass as well; SDSU warns homeowners not to buy lawn weed products containing glyphosate for that reason, since they will kill the lawn. With any herbicide or insecticide, the label directions are the law: the product has to be labeled for lawns, and the label sets the rate, timing and re-entry rules.

What conditions make a dandelion treatment work?

An actively growing weed. SDSU says these synthetic auxin herbicides need weeds actively growing, with daily highs of 60 to 85 degrees F for several days after application and lows above freezing, preferably above 40, plus adequate soil moisture. CSU's fall note adds that drought-stressed weeds respond poorly, so keep watering into fall. UNL recommends applying liquids to dry leaves and granules to wet leaves so they stick, applying when no rain is forecast, and sweeping any granules off pavement back onto the grass.

Drift and vapor are the risks. SDSU warns that ester formulations and dicamba are more volatile than 2,4-D amine and more likely to move off target as temperatures rise, and advises avoiding application in winds over 10 mph and near sensitive plants. CSU says trees and shrubs are rather sensitive to dicamba, so limit its use under woody plants. SDSU notes that waiting until after a light frost in fall lowers the drift risk to other plants in the yard.

Is weed and feed a good idea?

Usually not for dandelions. SDSU says applying nitrogen fertilizer at dandelion pre-bloom may inhibit lawn root development compared with feeding several weeks later, and a strong root system is what carries the lawn through summer drought. CSU says liquid spot treatments are generally more effective than weed-and-feed applications. MSU's own lawn guide puts the key Montana fertilizer timings around Memorial Day, Labor Day and a late application about four weeks before the soil freezes, which does not line up with a dandelion's pre-bloom stage. Our guide to fertilizer rates and timing has the details.

How do I keep dandelions from coming back?

Thicken the lawn. MSU says healthy turf can often outcompete weeds, and points to addressing soil compaction, nutrient needs and responsible turf care. SDSU's list is specific: overseed thin areas, mow at approximately 3 inches, remove no more than a third of the blade at a time, leave clippings, fertilize at the proper times and keep the lawn watered through summer stress. Our guides to mowing height and aeration and overseeding timing cover those steps.

Set realistic expectations. Dandelion seed blows in from neighboring lots, roadsides and fields, so complete eradication is not a sensible goal; a dense lawn simply gives arriving seed nowhere to root.

Can I treat dandelions in a new or recently seeded lawn?

Wait. Young grass is more easily injured than established turf, and the product label is the authority on how soon after seeding a lawn herbicide can be used. In a lawn seeded in late summer, the practical approach is to dig the few dandelions that appear, let the grass get through its first winter and spring, and treat in the following late summer or fall window MSU recommends.

The same caution applies after overseeding. Combining fall overseeding and fall weed control on the same patch needs planning around the label, so we schedule the two rather than doing both at once.

Should I leave some dandelions for pollinators?

That is a personal call, and extension sources acknowledge both sides. MSU notes some people embrace dandelions as a source of nectar and pollen for pollinators in urban landscapes. UMN says the quality of dandelion nectar and pollen is debated, but their early spring bloom can feed pollinators when little else is flowering. If that appeals to you, leaving dandelions in a rough edge while keeping the main lawn dense is a reasonable middle ground, and our guide to planting a pollinator garden in Montana offers better long-term forage.

Dandelion control from HJ

We are licensed for weed control and pesticide application. Our fertilizer and weed control program spot-treats dandelions and other broadleaf weeds in the fall window when it works best, and pairs that with aeration and overseeding so the gaps fill with grass. For the bigger picture of what else is growing in your lawn, see common lawn weeds in western Montana. This guide is part of our Montana Landscaping, Lawn & Irrigation Guide. Call (406) 215-7319 or request a free estimate.

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