Heavy thatch of Bermuda grass needs to be eliminated

Q: I have a problem with my backyard lawn that I hope you can help me with. I live in Henderson and the lawn has a soft spongy feel to it. When you walk on it you kind of sink into it. It is Bermuda but we overseed it with ryegrass in the fall. It has been like this for the last six months. The lawn was aerated and thatched before over seeding. My front lawn is fescue and doesn’t have this problem. Any ideas?

A: Even though it was “dethatched,” it sounds like there is still quite a layer of existing thatch in the Bermuda grass. Bermuda grass requires that this thatch layer be reduced or nearly eliminated annually or perhaps every other year. When this thatch layer gets over about half an inch thick, it produces a spongy layer that feels like you are walking on a cushion.

Some grasses produce lots of thatch and others are not heavy thatch producers. Tall fescue produces little thatch and so requires dethatching infrequently, if at all. Thatch is a layer of undecomposed, but dead, turfgrass debris that lies on the surface of the soil. This debris decomposes very slowly because it comes from the tougher parts of the grass plant.

Mowing a lawn and leaving the clippings or leaf blades lying on the soil surface contributes very little to the buildup of thatch. Leaf clippings are tender and decompose quickly. Bermuda grass not only produces leaf blades, but supporting those leaf blades are the tougher stolons (sometimes called runners) and stems that support the leaf blades. These stolons and stems are continuously dying and subsequently regenerated by the turfgrass plants.

Tall fescue does not produce stolons but instead is considered a “bunch” grass or a grass that cannot spread along the surface of the ground through runners. Dead stolons or runners and tough grass stems are what contribute to thatch buildup over time.

Overfertilizing and overwatering stimulate Bermuda grass stolons and stems and thus contribute to more rapid buildup of thatch. We can regulate how fast Bermuda grass grows (and how much thatch it produces) by regulating our fertilizer and water applications. Use slow-release nitrogen fertilizers or use less expensive fertilizers that are not slow-release more often but in much smaller amounts than recommended on the bag. Apply water to Bermuda grass when you see or just prior to signs of water stress (smoky or blue-green leaf color).

When you overseed your lawn it is important that the dethatching is thorough enough so that you see bare soil when you are finished. If your Bermuda grass lawn has not been dethatched for a long time, the thatch buildup can be so thick (and feels very spongy) that if you were to try and remove the thatch you will remove the lawn. A Bermuda grass lawn will regenerate itself quickly after severe dethatching. Tall fescue lawns will not.

My guess is that your Bermuda grass lawn has not been adequately dethatched for quite awhile.

Q: Do the plants in our desert landscape need to be pruned, such as the bird of paradise, fountain grass, chaste tree and lantana? If so, how much and when?

A: The plants you mentioned do not need much pruning. Pruning is getting plants to grow how we want them to grow. If you are happy with them then I would not prune them much. Major pruning should be done in the winter. Minor pruning can be done any time.

Remove dead or broken plant parts. Remove them all the way to their point of origin and leave no stubs. Remove any growth that is extremely vigorous, and growth that is growing straight up or straight down.

Sterilize pruning tools with alcohol prior to use and make sure they are sharp and adjusted. Fountain grass should be cut back to about 12 inches high. Lantana, if out of control, can be trimmed back to a few inches of the soil if you like. Fertilize them with a basic tree and shrub fertilizer in January and water it in.

Q: My potted plants have been infested with a small, green and sometimes striped worms that are destroying the flowers and buds on my petunias, geraniums and verbenas. I pick them off when I see them, but never get them all. Is there something I can apply to destroy these worms? I would prefer not to use Sevin because of its toxicity.

A. Sounds like tobacco budworm. Try either Dipel, Thuricide or Spinosad. They are all organic, and they will work if you get them on at the right time. Mark your calendar for next year as they will probably be back around the same time each year. Follow label directions.

Q. We live in North Las Vegas and have a cherry tree that has a purple leaf in our front yard. Several were planted throughout our neighborhood, but I do not know of anyone eating the fruit.

Is this just a decorative cherry tree only? I can’t say that I’ve even seen birds eat the fruit.

A. I have had several people contact me about this tree. This is one of the purple leaf plum trees. It does have fruit that is edible but usually does not produce enough fruit or the fruit is not tasty enough to bother with. However, I do know people who make jelly with the fruit and have had some and it is quite good. In fact, I recently had a friend bring me a jar of purple leaf plum jelly, and I have to admit it was excellent.

So if you are so inclined, go ahead and sample the fruit. It will require quite a bit of sugar as they are sour but should be ready now. Most are falling off of the trees in the area. Birds like sweeter fruit.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce.unc.edu.