Neil Sperry

Answers to the most common gardening questions that come up during the early summer

Summer brings on its own unique set of gardening questions. I’ve chosen several that keep coming up in my life and I’ll provide you the answers I give.

My St. Augustine is yellowing in patches. What causes that, and how can I correct it?

You’re in that overlap time. Take all root rot is wrapping up for the springtime. Rains and cool late-spring weather kept it around longer than usual. It causes St. Augustine and zoysia to be yellowed in very random patterns. In several cases the grass may even pull loose easily from the soil if the runners’ roots have been severely damaged by the fungus. If you feel the disease is still active, the fungicide Azoxystrobin (sold at the consumer level as Scott’s Disease EX) might still offer help.

The disease that’s just starting to show up across Texas as the temperatures climb is another fungus called gray leaf spot. It also causes yellowed turf, but the patches are far less distinct. It causes diamond-shaped, gray/brown lesions along the midribs of the blades and sometimes even on the runners. It is exacerbated by application of nitrogen in hot weather, so it’s best not to fertilize St. Augustine from mid-June through early September. Fungicides labeled for use on leaf spots on turf will generally help with it, but avoiding nitrogen is your best long-term solution.

What is the best way to get rid of nutgrass?

First, be sure of the plant you’re trying to control. If it has triangular stems, you have nutsedge, not a true grass. Grasses have round stems. Things that kill grasses typically don’t work as well on sedges. Ask your nursery, hardware or feed store professional for a product to control sedges. You’ll see names like Sedgehammer, Sedge Ender and Image. Read and follow label directions carefully for the best results.

Why aren’t my crape myrtles blooming?

There are several possible reasons. It may be the variety. Some types bloom much earlier than others. You may have late types. If you pruned your plants last winter, especially if you topped them, you set their date of first bloom back by six or seven weeks. If they’re growing in shade that will slow or prevent their blooming, so check to see if your shade trees have grown considerably larger. And sometimes older plants just don’t grow as rapidly as new plantings. Flowers are produced on new shoot tips. Feed your plants to encourage new growth and, hopefully, blooms.

Why aren’t my tomatoes setting fruit?

You may have planted the wrong varieties. Large-fruiting types are destined to disappoint due to summer’s high temperatures. They are physiologically incapable of setting fruit when temperatures go up over 90 degrees. Varieties like Big Boy, Beefsteak and the large heirloom types should never be sold here. You’ll get five or six fruit before they shut down from the heat.

Tomatoes are pollinated by agitation. It’s possible that your plants aren’t being vibrated by the wind. You can accomplish that by thumping the flower clusters every couple of days. It will work perfectly on smaller types and it may help on the large types.

Why are my marigold plants looking like straw and dying? Their soil is never dry, so that’s not the problem.

They’ve been hit by spider mites. The nearly microscopic pests suck the color and life right out of the leaves of marigolds, tomatoes, beans, squash, violets and dozens of other garden and houseplants. We lost our great miticide Kelthane several years ago, so you’ll need to use a general-purpose insecticide that is also labeled for use on spider mites, also known as “red spiders.” If you want to see what they look like, thump a leaf over a sheet of white paper. You’ll see the tiny pests start to move.

Is there a rose variety that is immune to rosette virus? Is it safe to replant after I have taken the infected plants out?

Research is still in process to identify ways to work around this devastating virus. It’s been a problem all around the world for some time, but it seems like we in the Metroplex have had far more than our share of it.

At this point there still are no recommendations of varieties to use for replantings. If you’re willing to plant knowing that your roses may not last as long as you would like, you can certainly try them. Howevcr, look over the stock at the nursery carefully before you invest. It’s rather late in the season to be planting for this year. You might be better served with some other type of plants.

Dwarf crape myrtles are a great choice. They grow to about the same height and width as roses and they bloom in generally the same colors. Like roses, they lose their leaves in the winter, but they bloom for a longer period of time from late spring through early fall.

How can I eliminate dalligrass from my lawn?

As things stand now, we have no herbicide that is selective enough to kill one grass (dallisgrass) within another grass (your lawn). You’re going to have dead spots one way or the other.

Option 1 is to dig out the dallisgrass clumps by hand. Do so as soon as you see them and certainly before they get large enough to start producing seed.

Option 2 is to cut the bottom out of a 1-gallon milk bottle. Mix a spray tank of glyphosate (no other active ingredient mixed in with the herbicide) in a pump sprayer. Push the jug down over the dallisgrass clump and insert the spray wand into the top of the bottle. Spray the weed while using the jug to prevent the spray from drifting where it’s not wanted. Move from clump to clump. Sure, it will leave brown spots, but they’ll soon re-cover with your permanent turf.

You can hear Neil Sperry on KLIF 570AM on Saturday afternoons 1-3 pm and on WBAP 820AM Sunday mornings 8-10 am. Join him at and follow him on Facebook.