Never put your Las Vegas lawn to bed wet

Q: I read with interest your column in the Review-Journal on watering. Our small lawn seems to be dying in patches. We water four days a week for 20 minutes at 11 p.m. We regularly feed with Turf Builder Plus and Ironite. What should we do?

A: First of all, change your watering time to 4 a.m. and finish before sunrise. Never put your lawn to bed at night wet. You are asking for disease problems if you do.

Most warm weather lawn diseases need about six hours of a damp, dark, warm environment to get active. After a watering cycle, wait 30 minutes and push a long piece of rebar or screwdriver into the lawn in several locations. Make sure it pushes easily to 10 to 12 inches before you meet much resistance. If it does, then you are watering deep enough. If not, increase you watering until you can push it that deep. If deeper than this, reduce the minutes to 15 or so and repeat.

Break your 20-minute cycle into three shorter cycles totaling 20 minutes and space them about 15 minutes apart. This helps prevent puddling and runoff.

This fall, rent a core aerifier and punch holes in the lawn. Aerate your lawn every three to four years; more often if your lawn gets a lot of foot traffic.

In lawns, nearly any iron product works so you don’€™t have to spend a lot of money on iron. Not true about other plants.

Q: I want to plant potatoes here in Vegas. Our season is timed differently than others though, so there aren't seed potatoes available now for a mid- or late-July planting. Will standard Yukon Gold, russet, fingerlings or sweet potatoes from the grocery survive here? Or can you suggest where to get some suitable seed potatoes?

A: You are planting too late if you put them in the ground in July. We need to plant Irish potatoes here in late February or early March. Purchase seed potatoes early in the spring. Sweet potatoes are a hot weather crop and need to go in later when soil temperatures are warm, around the first week in late April or early May.

Any Irish potato can be quartered and used for ’€œseed.’€ Potato seeds are not seeds at all but cut up potato tubers. When cutting potato tubers for seed, make sure each seed piece has at least two ’€œeyes’€ or ’€œdimples’€ and plenty of tuber connected to it.

Sterilize knives used for cutting and allow the cut pieces to ’€œheal’€ in the refrigerator, moistened, for a few days prior to planting. Warm up seed pieces taken from the refrigerator to room temperature before planting.

I have used potatoes from the grocery stores for seed, but you should realize that they are not certified disease free so diseases are more of a potential problem. Purchase organic potatoes for seed since standard potatoes may be treated with a sprout inhibitor. Sprout inhibitors are sometimes applied to keep them from sprouting in storage.

All of the potatoes you mentioned will grow here including sweet potatoes. Consider Red Pontiac and Red La Sota for red-skinned potatoes as well as those you mention. Also try blue potatoes such as Adirondack Blue as well as fingerlings.

If you’€™re going to grow potatoes here, make them really special because regular old potatoes are not terribly expensive to purchase. I don’€™t know of a potato that will not grow here.

Q: I have Italian cypress that my gardener said were attacked by spider mites. I asked at a nursery and was told they will never green up. My wife is certain they will. I would like to know who is right: the gardener, the nursery or my wife.

A: Are you kidding? Always side with your wife. Without seeing them and the extent of damage, it is hard to judge but wait and see if they green up. If the damage has extended all the way into old growth, they probably will not recover. If there is some green growth remaining it is possible for them to slowly recover.

During summers, hose down the trees once a month or after any kind of dirt storm. Dirt or dust on the leaves interferes with the natural control of spider mites by predatory mites and beneficial insects. There is a natural ecosystem at work on cypress that keeps the bad critters like spider mites under control.

Do not water Italian cypress too often. Watering frequently can cause root damage and create a similar type of browning. These are Mediterranean plants and do not tolerate wet soil. Water them no more than once a week if you have a normal soil, but give them a deep watering when you do.

Take the branches with dried needles and bend them. If they are dry and snap, they will not recover. If they are supple and do not snap like a dry twig, they may recover. That is the best I can tell you. I would have to see the foliage very closely and inspect it for mite residues to conclude if the damage was from spider mites are not.

Q: I live in a subdivision with 400 townhomes and a fair amount of grass that the homeowners association maintains. The lawn crew does a couple of things that I question. They keep the grass mowed pretty short — 1½ inches. Shouldn't they wait until it gets about 3 inches and then cut only 1 inch off? Wouldn't this minimize evaporation?

They are collecting the clippings and discarding them. Wouldn't it be better for the lawn if the clippings fall back on the grass? Doesn't the nitrogen recycle back into the lawn?

A: They should be recycling the clippings back into the lawn and mowing higher. This will require that they use recycling mowers, a special blend of fertilizer with half of its nitrogen in the slow release form and closer lawn management.

Mow tall fescue no closer than 1½ inch at any time and 2 inches is better. This gives them ½ inch of growth they can remove safely each mowing. These grass blades contain a lot of fertilizer that ends up in the landfill, so it is better to recycle them back into the lawn.

If removed clippings are an inch long, this tells me the nitrogen fertilizer applied is excessive. No more than 1/3 to 1/4 of the grass blades should be removed in one cutting. Measuring the average length of clippings is a good way to determine if nitrogen fertilizer is needed by a lawn or not.

Mowing is important for controlling lawn diseases. Grasses are unique because they push growth from the bottom of the blade; the oldest growth is removed when mowing. Old-growth contains more disease problems than the newest growth.

Lawn clippings can and should be returned to the lawn. If they do this successfully they must use recycling mowers and a quality lawn fertilizer.

Returning lawn clippings to the lawn substitutes for one fertilizer application every year. Recycling lawn clippings back into the lawn improves its general health because lawn clippings are composted back into the soil, releasing nutrients.

Recycling mowers have a unique blade and a unique deck design that provides greater lift and causes lawn clippings to be chopped up more effectively than with traditional mowers. Traditional mowers retrofitted with recycling blades will work, but they are not as efficient as recycling mowers.

If a recycling program is done correctly, you will not see any residue from lawn clippings left on the lawn after mowing.

Fertilizers used with recycling mowers are unique. They must have a large percentage of their nitrogen in a slow release form or the fertilizer should be applied in much smaller quantities, more often. Their greater cost is offset because less fertilizer is required.

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. Send questions to Extremehort@aol.com.