Why is fall actually the best time to deal with dandelions instead of waiting for spring?
Dandelions are perennial weeds, and in early fall they’re pulling their energy downward into their roots to get ready for winter. University of Missouri Extension explains that this is when most of the plant’s activity moves into that big taproot underneath it, which means weed treatment applied now has a better shot at reaching the root instead of just sitting on the leaves. CSU’s PlantTalk Colorado backs up the timing for our area too, calling late summer and early fall the best window for dealing with dandelions and other broadleaf lawn weeds.
At Clean Air Lawn Care, we treat weeds with Moose Juice, our own bio-based weed blend. It’s made without synthetic pesticides and without 2,4-D, dicamba, or MCPP, the three ingredients most conventional weed products rely on. Moose Juice is a liquid treatment, and like every liquid product we use, including our fertilizer with pre-emergent, it comes with a 24-hour no-water rule after it’s applied. Luke DeLongchamps performs Moose Juice treatments for Fort Collins, Windsor and Timnath customers during this same fall window that PlantTalk and the University of Missouri point to as the best time for dandelions. We haven’t independently tested whether Moose Juice moves into the root the same way the conventional products described above do, so we’re not claiming that specific mechanism for it. The fall timing itself comes straight from PlantTalk and university research. This holds true across Fort Collins, Windsor, and Timnath lawns, whether you’ve got turf-type tall fescue or Kentucky bluegrass.
The mix-up that trips people up
A lot of homeowners put down crabgrass preventer in spring and expect it to take care of dandelions too. It won’t. Dandelions, clover, and spurge are broadleaf weeds. Crabgrass is a completely different kind of weed, a grass, and an annual one. A crabgrass preventer stops grass seed from sprouting in the soil. It doesn’t do anything to an already-growing broadleaf weed like a dandelion. Different weed, different tool, different season.
Why fall beats a summer treatment
There’s another practical reason fall works well: by this time of year, a lot of summer weeds are already dying off on their own. A couple of hard frosts will kill off weeds like crabgrass and purslane without you doing anything. Dandelions and other perennials stick around through frost, though, which makes them exactly the ones worth targeting now.
What goes into a fall weed treatment
A few standard practices apply, regardless of the exact product:
- Temperature matters. PlantTalk Colorado recommends using herbicide when it’s between 65 and 85 degrees.
- Spot-treat, don’t spray the whole lawn. PlantTalk recommends treating individual plants or the specific spots where weeds are, rather than spraying the entire yard.
- Watch the weather. PlantTalk’s own guidance is specific here: don’t apply if rain is expected within 24 hours, and don’t water the treated spot for 24 hours afterward. That’s also our own standing rule for Moose Juice specifically, since it’s a liquid product.
- A thick lawn is your best long-term defense. Healthy, dense grass crowds weeds out before they can get established. Watering, mowing, and fertilizing the right way all help build that density, it’s exactly what our own organic, non-toxic fertilizer program is aimed at.
A season-long plan, not one treatment
A full weed program usually means a spring crabgrass pre-emergent for grassy weeds and a fall broadleaf treatment for dandelions and other perennials, paired with consistent watering, generally 1 to 2 inches a week, up to 2 inches during the mid-July to mid-August peak, across two or three deep waterings. That combination keeps the lawn thick enough that weeds have less room to move in.
Dandelions are the one thing almost everyone in Fort Collins, Windsor and Timnath asks us about at some point, usually right after they realize spring treatment never touched them. Fall is genuinely the better window, and it is not a sales pitch, it is just how the plant works this time of year. If your lawn is loaded with dandelions right now, let’s talk about getting ahead of them before winter.
Clean Air Lawn Care Northern Colorado is owned by Dianne, Paul, and Luke DeLongchamps — a family business serving Fort Collins, Windsor, and Timnath with organic lawn treatments and solar-powered electric equipment.
