Bermuda grass performs best when it’s taller

Q: I can’t get my Bermuda grass lawn to look good. I would like it more like a golf course grass. I think one of my problems has been mowing too low, believing it would green up if I did this. During the past two weeks I’ve raised the height of my mower and fertilized. It is looking much better, but it probably needs another week of growing. I’m getting small patches of darker green grass with a wider leaf. I think this is what they call Poa. There’s probably little I can do to stop this Poa weed.

A: Depending on the kind of Bermuda grass, it could be mowed as tall as 1 inch in height. However, most Bermuda grasses perform very well cut at about ½ inch in height. Lower than this is for the professionals, in my opinion, and requires very frequent mowing, dethatching, a grass catcher and fertilizing frequently to look good.

The lower you cut the grass, the more often it needs to be mowed. When you have a thatch problem, mowing low will make the grass look worse. You really have to dethatch on a regular basis in the fall if you want it to look good.

If you don’t overseed, the best time to dethatch would be in late summer (August) so that the grass has time to mend before winter sets in. After dethatching, fertilize and water heavily to speed up the repair process. If you overseed Bermuda, then overseed in mid-September.

Yes, the small dark green patches with light green seed heads on the top are Poa. It is Poa annua, a very tough grassy weed to control in lawns. The seed spreads everywhere . This results in dark green Poa spots in a Bermuda grass lawn. If your Bermuda grass is an improved type, you can green it up by dethatching in the fall and applying nitrogen and iron fertilizers. It just makes the grass darker and the Poa harder to see.

Poa is a cool-season grassy weed. If you don’t overseed the Bermuda, you could spray it out in December or January with Roundup when the Bermuda is dormant but the Poa is still green. The problem will be the abundance of Poa seed produced; it will come back.

One benefit of overseeding Bermuda grass in the fall is the necessary removal of the thatch layer during the overseeding process. Excessive amounts of thatch will prevent a lawn from ever becoming dark green, even with lots of fertilizer.

Q: Some of the leaves on my Thompson seedless grapes have started to curl or cup. There is more curling on the newer leaves, and the curling is only on one side of the plant. The Red Flame grapes near them are OK . These were planted two years ago and watered on a drip line three times a week, for one hour each time. Each plant has two, 1-gallon drippers and receives 6 gallons of water per week. Is that sufficient? Both plants have several bunches of grapes, and I already have pinched off the bottom third of each grape bunch to make the berries bigger. Any advice would be appreciated.

A: It sounds like you are doing a great job, and from the looks of the pictures you sent, your plants are thriving. These will be posted on my blog.

Six gallons of water a week is a bit light in my opinion, but watch the plants, particularly the growing tendrils, and they will tell you.

If you are getting good vigorous growth from 6 gallons, then it is enough, and I would not change your watering until the plants get larger. Big plants need more water than little plants, so you will increase the amount they get at each watering by increasing the number of minutes or adding an emitter.

Grapes are naturally deep-rooted plants with roots that can go down dozens of feet. In our landscapes it doesn’t make much sense to water deeply to accommodate for deep roots .

You are watering only to a depth of about 18 inches. Watering three times a week at this time of year with this rooting depth makes sense to me. But you must maintain good soil moisture during and up to fruit harvest. Mulching helps in our climate.

We do have two types of early thinning for table grapes: reducing the total number of clusters on the vine and pinching off the bottom third of each bunch. This is done when the berries are still very small and help make the individual berries in the bunch bigger.

Wine grapes are thinned only the first way since we are not concerned with getting larger-sized berries.

Leaf cupping occurs while young leaves are developing since the cupping results from the overgrowth of the leaf center when the edges cannot keep up .

There are three primary reasons for leaf cupping. First is damage from a chemical growth regulator that drifted on to your vines. Since only one side of the grape plant was affected, this is a possibility.

Some lawn weed killers contain a growth regulator, called 2,4-D, which, at high concentrations, is a dandelion killer. When someone uses this herbicide on a windy day it can drift on to your property . This type of damage is usually not deadly, but causes leaf distortion. The leaves will be like that until they fall off the vine. The fruit is safe to eat, and next year the vines will be fine.

A second possibility is insects that cause plant leaf cupping when they are feeding. But if you see no insect problems, then we can probably eliminate this possibility. Anyway, aphids are not common on grapes.

This leaves the third possibility. If the leaves were just coming out and something damaged the edges, such as hot, dry winds or lack of water, then this could explain the cupping. The damaged leaf edge would not be able to grow, or it would grow slowly. The inside of the leaf would expand or grow, causing cupping.

The cupping would be worse as it grew. And this would only happen to young leaves that are still growing . But the cupping would be present all season long.

You should check to make sure the vines are getting enough water, particularly in the spring when temperatures are rising rapidly. If they were droughty, the leaf edges would scorch and cupping would result as well.

It might be a good idea to change your drip emitters to 2-gallon-per-hour emitters or higher, or increase the number of minutes, and apply a surface mulch to reduce water loss from the soil.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.