Considering using pre-emergent? Here’s what you should know

SALT LAKE CITY — It’s time to prepare your lawns so that they look healthy and green for the summer, and one thing you can do is spray pre-emergent to prevent weeds.

If you’re doing it on your own, the time to spray is the end of March to the first or second week of April, said KSL Greenhouse host Taun Beddes.

“If you do it now, it will be effective, but it may lose its effectiveness sooner when the weather warms up.”

Another option is to coordinate with a lawn care company. However, Beddes said this will require working with the company’s schedule due to the likelihood of there being hundreds of other customers needing the same service around this time of year.

Consider this before using pre-emergent

Beddes said the first question you should ask yourself is “Why are the weeds there?”

“You can use a pre-emergent to help control them, but those weeds are in your lawn due to mismanagement. And it’s unintentional, but a lot of times our sprinkling system isn’t watering correctly and so we get weeds in areas that are getting too much or too little water, our soil might be compacted, we could be mowing too low, and so we need to be thinking about the bigger picture.”

After you figure out the cause of the weeds and find a way to fix it, you can use a pre-emergent as the next step to help your lawn get healthier.

What to look for

Not all pre-emergents are the same, but most of them are effective on annual grasses that bloom or germinate in the spring, such as crabgrass and foxtail.

“So you have Dimension, Preen, Scotts Halts, Barricade. All of those are going to do really good against the grassy weeds. But if you have the broadleaf weeds like spurge and also black medic … wood sorrel is another one … Isoxaben is another pre-emergent. It’s a little less common, but you can still find it.”

Isoxaben is an active ingredient that is found in BioAdvanced’s Season Long Weed Control for Lawns and Fertilome’s Broadleaf Weed Control with Gallery. Both are usually available at independent garden centers and farm stores.

When to spray

“If you can time it with the rain or snowstorm, that’s great. And if you’re wanting to know exactly when to get it down, [there are] some cues you can look at,” Beddes said.

For forsythias, you can spray when it’s about done blooming and the flowers are fading. For lilacs, if they leaf out and have flower buds, then you can spray.

“Or you can just get a kitchen thermometer and put it in several areas of your soil, and when the temperatures of the soil that your lawn is growing in are around 50 degrees (Fahrenheit), you can put it down then. And that’s actually the best way because once that soil temperature hits around 50 degrees, the crabgrass and spurge and other lawn weeds will be germinating within the next week to two weeks.”

While you can use a pre-emergent if you have a lot of lawn weeds, Beddes said it’s not always the best tool for making sure your lawn is in the best condition for the start of the season. So before you use it, think about whether there’s been some unintentional mismanagement that needs to be fixed first.

Read more from the KSL Greenhouse show:

• When to plant vegetables along the Wasatch Front
• When’s the best time to prune shrubs and hedges?
• All about roses: Types, bloom times, and care tips

KSL Greenhouse is live Saturdays from 8 a.m. to 11 a.m. Follow the show on Facebook, Instagram, and YouTube. You can also find more gardening info on our linktr.ee.