Wait until winter passes to prune grapes

A: I don’t like to finish pruning my grapes until about March 1. This is because I don’t know what kind of damage they will sustain this winter because of the cold and wind. If I prune them back to very short spurs or canes now, I run the risk of losing my crop or a majority of it.

I usually prune grapes in two steps in our climate; the first step I remove most of this last year’s growth down to about 18 to 24 inches long. Then I wait for the majority of the winter to pass.

The second step occurs close to the first week of March. This is the time when I prune the remainder of last year’s growth down to about 1 or 2 inches long if I am producing on spurs and about 12 to 15 inches long if I am producing on canes.

Do not cut your grapes back yet. Wait until the major cold weather has passed.

Q: Are there are any plants I need to prune or trim down before the frost comes to the Las Vegas Valley this year? I noticed that oleander suffers greatly from frost; foxglove, asparagus ferns, potato vine and a purple flower trumpet flowered plant are kissed when the frost comes. Should these be covered also?

A: Damage from frost will vary throughout the valley. There are places that are naturally cold spots and others in windy locations. These areas will be hit the hardest.

Then we have the variability of the weather. It was not too long ago that we had unusually warm winters where it hardly froze at all. Then we had a brutal winter with the coldest temperatures hitting us in February when plants were just waking up from dormancy.

Then we have variability in the plants themselves. As far as oleanders go, there are winter tender types and there are very cold tolerant types.

My basic advice is to leave most ornamental plants alone. Wait until the coldest part of the winter has passed, or you begin to see the beginnings of new growth, and then remove what has been damaged. Oleander and asparagus fern can be pruned to within a few inches of the ground and they will recover.

This doesn’t hold true with citrus. Citrus planted in cold locations will have to be protected if you want them to survive or you want fruit.

Q: Some of my California Wonder bell peppers are turning half black instead of red. Otherwise, they seem fine. It seems to happens the most when it cools down. Are they safe to eat?

A: There is a huge assortment in bell peppers. Years ago they all stayed green and when they ripened, they became partially red. People liked them. The market grew for red bell peppers.

Then breeders bred for the development of a solid, red color. Now we have beautiful red peppers that are held on the plant a little longer to get that red color to develop. The same was true of yellow, orange and even purple peppers.

But nearly all of the bell peppers start off green. Producers harvest them when they are large but immature so they stay green. If producers spend a little bit of money for seed, get hybrids that turn a beautiful solid color and leave them on the plant long enough, they will get more money for them. And you get charged more at the store.

We harvest peppers before they are mature if we want them green. However, if we get a cold snap, this may cause them to develop their mature color sooner. In your case, I am guessing you have a pepper that turns dark purple when it is mature.

The clue was it was half black instead of red. Your pepper is just fine to eat and it actually might be a little sweeter because of the cool weather. By the way, that purple color is probably anthocyanin, a rich antioxidant.

Q: Two of my Indian hawthorn bushes developed unhealthy looking brown spots on their leaves. None of the bushes get a great deal of direct sunlight, but bushes on both ends of the row are looking all right. Can you tell me what is wrong with these two bushes and how to fix it?

A: From the picture this looks like a soil-related issue. The soil around the plant looks like it is fairly rocky and I am guessing unimproved over the years.

I think you’ll see a big response by taking a bag of decent compost and spreading it under the plants 1 or 2 inches thick and watering it in.

You also might try replacing any rock mulch under the plants with wood chips that will slowly decompose and improve the soil. If you put the compost down now and water it in, you should see some improvement in the plant when it continues growing in the spring.

The second thing you could try doing is spraying the foliage with a good-quality liquid fertilizer. Miracle Gro or Peters would be a good choice. Use 1 or 2 teaspoons of liquid detergent in a gallon of fertilizer spray to help it penetrate the leaf surfaces.

I would try spraying the foliage during the winter. It will take several applications a few days apart. If it’s in a warm spot, you may see a response before next spring. Otherwise you’ll have to wait until growth resumes early next year.

Q: What does a lawn need this time of year?

A: You didn’t tell me what kind of lawn you have so I will assume it is tall fescue or an overseeded Bermudagrass. I like to recommend your final application of fertilizer for the year right around Thanksgiving. This last application of a high-nitrogen fertilizer helps keep it dark green through the winter.

This application must go on before it gets really cold. If you wait too long and apply it later in December you run the risk that your lawn will enter into dormancy and start turning brown. Once it turns brown, it is difficult to get it green again until temperatures begin to warm.

Hopefully you have been applying a decent lawn fertilizer through the year. Good turfgrass fertilizers have half of their nitrogen content in the organic form or slow release. They also are relatively low in phosphorus compared to the other numbers. If you have been using good turfgrass fertilizers through the year, all you need to apply is a straight nitrogen, such as ammonium sulfate or blood meal for organic growers.

The usual rates recommended on the bag, in my opinion, are much too high. You can usually reduce that rate by 25 percent easily. If you are returning your lawn clippings to the lawn with a mulching mower, you can reduce it to half of the recommended rate.

You missed the ideal time to remove thatch with a dethatcher. That should’ve been done in mid-September to the first part of October. You can aerate your lawn or punch holes in it with an aerator any time of the year but mid- to late-spring is a great time for that.

Q: My Japanese blueberry trees look awful. They have dead leaves, are very open and look like they are dying. Any ideas on what I can do to bring them back to life?

A: Japanese blueberries don’t belong in our desert environment in my opinion, so if you are going to grow them you need lots of soil improvement, several inches of wood mulch, protection from late afternoon sun and an irrigation system and scheduling that does not allow the soil to become overly dry.

If these plants are getting late afternoon sun against a hot wall, such as one that is facing south or west, it is going to be very difficult to keep them looking good. If this wall is facing north or east you’ll have a much easier time of it.

Check the irrigation system and make sure that it’s adequate. Bring in 2 to 3 inches of compost and lay it on the soil surface. Cover this area with wood mulch 2 to 3 inches deep.

This will help, but it may take one growing season before they start to come back if they have not been attacked by borers. Check for borer damage and remove it or replace the plants if it is extensive.

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.