Neil Sperry

The Garden Guru: Spring’s burning questions

St. Augustine thins in shade.jpg
St. Augustine thins in shade.jpg Neil Sperry

It seems like questions are coming out of the woodwork.

Suddenly we have better weather, and gardeners are awakening to a new growing season.

Here are the questions I’m hearing most often. Hopefully several will be of help to you.

How can I get rid of the unending weeds?

Grassy weeds like annual bluegrass (Poa annua), rescuegrass and ryegrass must run their course at this point. There is nothing you can apply to them now that will kill them without damaging lawngrass. Resolve to apply a pre-emergent weedkiller (Dimension, Team or Halts) the first week of September to prevent germination of the next generation of weeds.

As for nongrassy weeds like thistles, clover, dandelions and chickweed, close mowing will eliminate most of them. You can also apply a post-emergent broadleafed weedkiller spray containing 2,4-D.

Is it too late to apply pre-emergent weedkillers?

A lot of people didn’t get the job done this spring because we had ice followed by snow, then rain. For summertime weeds like crabgrass and grassburs, you would apply a pre-emergent herbicide (Dimension, Team or Halts) the first 10 days of March.

Unfortunately, here it is a month later and people are still asking whether there’s any justification for applying them now. I don’t really have the perfect answer. Yes, you will still get some manner of help from the products, but they won’t do a perfect job of preventing the weeds. Many summer weeds are already sprouted and growing. So, I’ll leave this decision up to you.

What should I do to get my beds ready for flowers and groundcovers?

Apply a glyphosate-only weedkiller to eliminate existing turf and weeds. Allow it to stay in place for 10 to 15 days, then till to 12 inches deep using a rear-tine rototiller.

Incorporate 4 to 6 inches of organic matter, including sphagnum peat moss, compost, rotted manure and finely ground pine bark mulch. If you’re amending a heavy clay soil, include an inch of expanded shale as you’re tilling.

What secrets do I need to succeed with tomatoes?

They’re fairly simple and pretty basic:

▪ Plant small to mid-size varieties.

▪ Give them full sun.

▪ Provide well-prepared garden soil with several inches of organic matter.

▪ Grow them in 16- to 18-inch cages sized 4 feet tall.

▪ Give them constant moisture, but perfect drainage.

▪ Use a high-nitrogen or all-nitrogen fertilizer.

▪ Deal with insect or disease problems as they arise.

What type of fertilizer should I use for my flowers, vegetables and lawn?

The only way to know precisely is with soil tests through the Texas A&M soil-testing lab in College Station (instructions available at

However, for most of our North Texas clay soils, results will show that you need an all-nitrogen fertilizer in which half or more of the nitrogen is in slow-release form (coated or encapsulated).

What tricks are there to getting grass to grow in the shade?

Of all the questions I am asked year in and year out, this is by far the most common. St. Augustine is our most shade-tolerant grass, but even it must have four to six hours of bright, direct sunlight daily to survive. Zoysias need six to eight hours. Bermuda varieties need eight.

You can try removing one or two lower branches, but don’t disfigure your tree in the process. There comes a time when it’s just a lot easier to put in a shade-loving groundcover bed with mondograss, liriope, ferns, purple wintercreeper or other groundcover that can handle the darkness.

Is there anything I can do to help my new red oak tree survive and grow to its potential?

Stake and guy the tree to keep it perfectly plumb. Run the cable through a short piece of old tubing or rubber hose to protect the trunk. Leave the cable in place for one to two years, but not long enough that it can girdle the expanding tree trunk. Protect the tree against sunscald and invasion by borers.

Red oaks have very thin bark, and the south and west sides of newly planted trees will often burn in the sun’s intense rays. The bark will split and crack open, and insects, diseases and eventually decay will gain entry.

Should I add soil or compost to the surface of my uneven lawn?

That will depend on how deep and wide the lower areas are. You might try smoothing it with a lawn roller after a heavy rain to see if you can even out some of the issues. Don’t do that repeatedly, however.

If there still are low spots, gather topsoil from elsewhere in your own landscape and use it to fill in. That way you won’t introduce weeds to your lawn, and the soil will be a perfect match. With a little luck, you won’t have to cover more than a small portion of the grass.

As for the compost, I would suggest saving that for use in flower and vegetable gardens as you work up their soil.

Neil Sperry publishes “Gardens Magazine” and hosts “Texas Gardening” from 8 to 10 a.m. Sunday on WBAP/820 AM. Reach him during those hours at 800-288-9227. Online: