Here are answers to important North Texas lawn-care topics, from top soil to bare spots

We’ve chatted here about lawn-care questions that keep coming up. Things like “How often should I water?” “What’s the best kind of lawngrass?” “Why can’t I get grass to grow beneath my shade trees?” Those are Hall-of-Fame questions in the gardening world.

But there are other questions that don’t rise quite to that level. They’re still really important if you’re the gardener who wants to ask them. So here they are along with my replies.

“Should I spread topsoil over my lawn? If so, when?”

This used to be a practice back in “Old Texas.” I can remember truckloads roaming through neighborhoods and people knocking on doors offering to drop off a load. More recently there were small yard signs saying there was “Topsoil for Sale — Leveling Lawns.”

Unless you have a lawn that is dreadfully uneven this is not a good plan. Even then, it would probably be better to spread only a thin layer of washed brick sand and let it filter through the grass to fill any shallow voids up to 1/2-inch deep. Anything deeper deserves better attention. Dig out the existing sod. Add enough topsoil to even things out, but allow enough room that you can replant the sod without creating a bump. Water the grass and press it down firmly to even it up. Note: anytime you buy topsoil to bring into your landscape insist that it be completely free of nutsedge (“nutgrass”).

“My tree has large roots coming up out of the grass. Can I spread soil to cover them up?”

No. They’ll grow right out of the new soil, and then you’ll have exposed roots and a mound of soil to go with them. I once had a friend who asked me to look at his tree. When I got to his house, I realized he’d tried this practice on a large silver maple — not once, not twice, but three times. He had a mound of ground that stood 6 inches above the rest of his lawn. Sadly, the tree died a couple of years later to another problem. He had to shovel out all the soil he’d hauled in.

When you have a tree with large surface roots, learn to live with them. Conceal as many as you can with groundcovers, but people will understand all the rest. Just move on to other concerns.

“Is aerating my lawn a good idea? If so, when should I do it?”

It can be a very good idea, but people expect miracles from it, often at the wrong times. Aeration is beneficial in removing thatch. That’s the undecomposed organic matter that forms between runners and soil, especially in bermuda lawns and most commonly when we don’t catch clippings, mow infrequently and apply inexpensive high-nitrogen fertilizers repeatedly.

Aeration can also help when soil has become compacted by heavy pedestrian or vehicular traffic.

Always use a core aerator (one that pulls a small plug up and out of the soil as opposed to poking holes into the soil). April or May would be ideal times, but you can really do it at any time.

“Can I overseed bermuda to encourage it to cover more thickly?”

Not without preparing a good seedbed. We’re used to overseeding bermuda or, less commonly, St. Augustine with ryegrass for green winter turf. But ryegrass seeds are huge compared to those of bermuda. Seeding bermuda directly back into a bermuda lawn is not going to work. The bermuda seed is simply too tiny. It can’t compete for light with the established turf, and it will also wash away in heavy rains or irrigation if it’s not planted into a well-prepared planting bed.

“Is it better to mow my St. Augustine a little taller in the shade? It’s getting thin.”

Yes. St. Augustine blades will be more vertical when they’re in darker conditions. However, it may be cumbersome to have to adjust the mower each time that you cut your lawn. How about compromising and mowing the St. Augustine at 2-1/2 or 3 inches? That should solve both problems.

“I’m planting new bermuda sod. Do I have to rototill the ground, or can I lay the sod directly over the bare soil?”

My turf professor in college drilled into our brains that “…soil preparation for new turf is exactly the same, whether you’re going to sod, hydromulch or seed it. You need to rototill 2 to 3 inches deep, then use a garden rake turned upside down to smooth it out. Then you can plant your new grass carefully and start watering it regularly.” He noted that he had made no mention of how we’d be planting the grass.

“I see grass seed being sold as a type of patch for bare spots. Is that a good product?”

Oh, be really careful. Most of those are mixtures of several kinds of grass seeds. A lot of those types won’t even grow well here in North Central Texas. Some will become aggressive invaders into your “good” grass. Some will be green in the winter while your permanent lawn is brown. You really don’t want to use these. If you have a common bermudagrass lawn, you can plant common bermuda seed into bare spots as long as you prepare the soil properly. Or you can always buy sod or plugs to fill in the holes. Otherwise, don’t be buying the seed mixes.

This story was originally published April 28, 2023 at 6:00 AM.