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Delay final pruning of grapes as long as possible

Delay pruning your grapevines a little bit longer. You can cut them back now, but hold off on their final pruning length until after March 1. The idea is to delay the final pruning of grapes as long as possible before new growth begins. This helps reduce disease problems from developing on the grape bunches later.

If there is wet or rainy weather in the next few weeks, the disease may develop in your bunches of grapes even though everything appears normal. That’s what happened this past year.

To cut them back, identify the growth on your vines that occurred last year. This growth will be a different color than other vine growth.

Sanitize and sharpen pruning shears before cutting back any grapevine growth. If you don’t sanitize your pruners, you might spread disease from cut to cut. Right now, cut this new growth now to about 18 inches long. But this is not the final cut.

Cutting back this long growth helps you to see where to make the final cuts around the first week of March. You will perform these final cuts after March 1. You will see buds swelling on the grapes now but don’t get nervous. These buds will show some swelling and whiteness a couple of weeks before you must prune.

The final pruning cuts on grapes depends on the kind of grape that you have. Some new growth is cut back very short for spur pruning while others are cut longer if cane pruning grapes, usually 8 to 10 inches long. Thompson seedless, for instance, is normally cane pruned leaving 8 to 10 inches of new growth while the new growth of most wine grapes is spur pruned (very short).

Q: I have two grapevines, one white and one red. When and how should I fertilize these grape plants?

A: All grapes whether they are red, white or black are fertilized a couple of weeks before new growth begins. Your visual key to apply fertilizer is the swelling of buds for new growth. This gets the fertilizer in place and ready to be pulled into the plant by the plant roots when the plant is ready to grow. If you haven’t already done it, fertilize it now.

The fertilizer — whether you are using conventional granular, compost or organic types like fish emulsion — should be in contact with wet soil after it is applied. This means if your fertilizer is “fluffy,” like compost, any surface mulch is raked back, and the compost applied to the soil surface where the soil will get wet.

Then rake the woodchips back and cover the soil again. Granular or liquid fertilizers like fish emulsion may be applied to the surface of mulch and washed through it to the irrigated area of the soil using a hose. Granular or liquid fertilizers are a little easier to apply than compost.

Granular fertilizers used for established lawns work well on young vines if the soil is covered with woodchips. Fertilizers used for tomatoes or roses work well on mature vines.

If you planted your grapevine with a good quality compost mixed in the backfill you may not need any fertilizer the first two or three years. Look at the grapevine and judge for yourself. If it had strong growth last year then apply a half application of fertilizer. If the vine is weak and not growing well, apply a full amount of fertilizer.

Grapes don’t grow well when surrounded by rock. Your grapes will perform better with less stress. In our desert soils, grapes prefer soil covered with woodchips.

If your grapes are surrounded by rock, I would strongly encourage you to rake it back, spread an inch of compost on the soil surface and cover the soil, at least 6 feet in diameter around the vine, with 4 inches of woodchips. Grapes struggle enough in our hot deserts without adding the extra stress from surface rock.

Apply fertilizers about 18 inches from the trunk or main stem of established vines so they don’t do any damage.

Q: We have buffalo grass for a lawn that we overseed every winter with ryegrass. We applied the ryegrass late this fall and it didn’t come up, but weeds did. Now our buffalo grass lawn is covered in weeds. Is it possible to apply a “Weed and Feed” product to kill all the weeds and not hurt the buffalo grass? If so, what would you recommend and when should this be applied?

A: Buffalo grass, like Bermuda grass, is considered a warm-season grass. It is native to the Great Plains of the U.S. and has a reputation for low water use. All warm-season grasses are brown in the winter because they are dormant due to cold weather.

As their name suggests, warm-season grasses prefer growing in warm or hot climates. Besides Bermuda grass and buffalo grass, other warm-season grasses include zoysia, Paspalum and St. Augustine grass among others. These grasses are sometimes called “southern grasses” because they are used primarily in southern states.

Warm-season grasses start turning brown in the cool fall months sometime in November and are totally brown here by December. Seeding a cool-season grass like ryegrass into a warm-season grass as it transitions to dormancy creates a green winter lawn.

You have two lawns in one during the winter: a green lawn actively growing in a brown lawn that is “sleeping.” The key for successful winter overseeding is good timing. A winter lawn of cool-season grass is seeded as the weather begins cooling off in the fall but you can’t wait until it’s cold.

The time for winter overseeding in this climate is between the end of September and mid-October. Your November timing was too late. If you have a warm November, it’s possible to make it but that’s not what happened. Last November was a cold month with unusually freezing temperatures around midmonth. It was too cold for successful overseeding.

Estimating when to overseed a lawn is like estimating when to put out tomatoes in the spring only in reverse. Pay attention to the current weather and weather predictions for the coming two weeks. If it’s unusually warm, delay overseeding a couple of weeks. If a cold front is coming in, then you better get busy and overseed.

Warm-season lawns like buffalo grass start to “wake up” and grow when it gets warm — March or early April here. Since the buffalo grass is dormant now (brown), any weed killer that kills green growth will not harm the dormant lawn.

The usual weed killer used for this purpose is glyphosate. Mow these weeds, but apply the weed killer in early March. A week or so after this weed killer has been sprayed, mow the lawn short, fertilize and water it to encourage faster green-up.

Q: I have a 5-year old prickly pear cactus. I brought it here from Florida in 2015 and started it by planting the pads. I’m seeing some yellowing starting to develop where the spines are located. I am familiar with cochineal scale and I don’t think it’s an insect problem. What’s causing this and how do I correct it?

A: Most likely this is cold damage from low winter temperatures. Most of Florida is warmer than our Las Vegas climate. Your prickly pear cactus from Florida has never seen temperatures as cold as we get in Las Vegas. Prickly pear, aka Opuntia cactus, ranges in its tolerance to freezing temperatures from damage seen at 32 degrees F down to 10 degrees. It depends where that cactus was originally growing.

Opuntia cactus is native to Central and North America with some types growing in the warm Sonoran Desert and others in our colder Mojave Desert. Pads used for propagating this cactus coming from the Sonoran Desert will not tolerate the freezing temperatures of the Mojave Desert. But Opuntia grown from pads taken from the Mojave Desert will.

In the future, don’t apply any fertilizer to tender Opuntia after July 1. Not applying late summer or fall fertilizers improves their ability to withstand freezing temperatures.

For a similar reason, start withholding water from Opuntia to slow growth in the early fall months. Not encouraging new growth by withholding fertilizer and water helps to harden them for the cold winter months.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.

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