When to Put Down Pre-Emergent in New Braunfels, San Marcos & Seguin (and Why the Bag Keeps Losing)

If you've bought weed and feed more than once for the same front yard, this post is for you. Every spring the crabgrass and spurge come back thicker than you can pull them, and every spring the bag goes down on a free Saturday. The problem usually isn't the product. It's the calendar.

Why timing beats product

A pre-emergent doesn't kill weeds. It forms a barrier in the top half inch of soil that stops weed seeds from sprouting. Once a seed has germinated, pre-emergent does nothing to it. That means the only thing that matters is whether the barrier was in place before the seeds woke up, and seeds wake up on soil temperature, not on your schedule.

Around New Braunfels, San Marcos and Seguin that happens earlier than most people think. Crabgrass, goosegrass and spurge start germinating when soil temperatures hold around 55 to 60°F, which on Comal County's thin limestone soil is usually mid to late March. A bag put down in April is already late. One put down in May is cleanup, not prevention.

The New Braunfels pre-emergent calendar

Here's how we time it on the Bermuda lawns we treat across New Braunfels, San Marcos, Seguin, Schertz, Cibolo and Marion:

• January to early February: the spring application, on dormant turf. This is the one that stops crabgrass and spurge, and it needs to be down before the soil warms. It carries about six months if it's watered in.
• June to mid July: a second application. Most programs skip this one, and it's why so many lawns here are clean in May and full of spurge in August. Spurge keeps germinating all summer, and the spring barrier runs out right when the heat and thin turf give it an opening.
• Late August to early October: the fall application, for poa annua, henbit, chickweed and the other winter weeds that sprout once nights cool off.
• October to mid November: a third, smaller application with the winterizer, as a second line of defense on poa.

Three windows, two different products so the weeds don't adapt to one, and every one of them timed to soil temperature rather than the calendar on the bag.

Does the timing change in San Marcos, Seguin, Schertz or Cibolo?

Not in any way that matters. The whole I-35 corridor from Schertz and Cibolo up through New Braunfels to San Marcos sits on the same climate, and soil temperatures cross 55°F within about a week of each other across it. The one local difference worth knowing: the heavier blackland clay east of I-35 around Seguin and Marion holds water and warms a little slower than the thin limestone soil on the New Braunfels and San Marcos side, so if anything you have a few extra days of margin there, not fewer. Our rule for every city we serve is the same: spring pre-emergent down by the first week of February, summer split in June, fall application in September. Kyle and Buda, if you're reading from there, run on the same calendar.

Why the bag can't keep that schedule

Store weed and feed combines fertilizer with a pre-emergent, which forces a compromise: the fertilizer wants to go down when Bermuda is actively growing (April onward), and the pre-emergent needs to go down in January or February when the grass is still brown. Put it down early and you're feeding dormant grass. Put it down when the grass needs feeding and the weeds have already sprouted. The product isn't bad. It just can't be in two places at once.

The other problem is water. Pre-emergent has to be watered in, about a quarter inch within a few days, to move it into the soil where seeds are. On an NBU one-day-a-week schedule that's fine if the application is timed ahead of your watering day. If it goes down the day after, it sits on the surface for a week, and some of it is gone before it ever activates.

What to expect the first year

Pre-emergent only works on weeds that haven't sprouted yet. So in year one, you'll still see the weeds that were already in the lawn, and the job is to control those while the barrier stops the next flush. Customers who stay on the calendar and water in each application usually have a dense, nearly weed-free lawn by the second spring. Anyone who promises weed-free in a few weeks is setting you up to quit in month three.

One of our customers, Myra, put it this way in her Google review: "I fought the weeds in my yard for years until I switched to Lemonade Lawn Care." Years, then one season on a calendar. That's the normal pattern.

If you want to do it yourself

You can. Buy a standalone pre-emergent (prodiamine is the common one at the box stores), not a weed and feed, and put it down in the last week of January regardless of what the lawn looks like. Water it in. Then do it again in June and again in September. Keep the fertilizer separate and start it in April. If you'd rather hand off the part that runs on a schedule and keep your mower, that's what our fertilization and weed control program is: eight visits a year, pre-emergent in all three windows, grub control included, starting at $58 per application with no contract.

Dave Brandt is the owner of Lemonade Lawn Care, a New Braunfels lawn care company founded in 2017 and voted Best Lawn Care Service in New Braunfels by Herald-Zeitung readers seven years running. Questions about your lawn? Call (830) 730-8022.