Low temperatures may cause oranges to freeze

Q: After six years, I am finally getting oranges. They are turning orange and I have been told not to pick them until mid-January. Is this right?

A: Different varieties ripen at different times. I would sample one now and if it tastes good to you then harvest the others at the same maturity. If it is not yet to your liking then wait a bit but if temperatures drop to the mid-20s then the fruit might freeze.

Play it by ear a bit right now but normally they would be ready right about now. You do not want to wait too long because fruit remaining on the tree can interfere with new flower production.

Q: I usually prune my grapes when I do the roses but would like to get a jump on it this year. Will I do them any harm if I prune them now?

A: You can do it but I worry a little bit about possible freezing damage if these are tender grapes and desiccation. I usually delay it until almost the first week in March when buds are starting to swell.

By delaying it I can prune out the dead wood that occurs during the cold winter months and focus on the stuff that is still alive. I would wait.

Q: I have some bushes and shrubs in my backyard. I also have yellow and red bells. They still seem to be blooming. How do I know when they are ready to be trimmed back?

A: Let them go through the winter and trim them back after you see signs of freezing. I usually recommend that you don’t do any pruning on these plants until all of the very cold weather has passed this winter. That is usually by mid-February.

Much of this depends on appearance. If it looks bad to you, go ahead and prune it back. You will not hurt the plant. My major concern if you prune too early because of freezing damage, you may get more freezing damage and will have to prune a second or third time.

Waiting until the end of the coldest part of the winter avoids this problem. But if you like to go out in the yard and tinker, prune when you need to. It won’t bother the plant.

Q: We were out in our yard last weekend when we noticed small bugs flying up out of our yard. They were so thick coming out of small holes that they looked like grains of rice clumped together in bunches; there had to be thousands of them. The “exodus” lasted for about an hour or more and then it was done, with no sign that they had even been there.

Can you tell what they are? Are they harmful? Do we need to do something to get rid of them?

A: These sound like winged ants or even possibly winged termites. They both swarm in identical fashions. You have to catch some of these insects and look at their body shape.

Ants have a constricted waist and three definite body parts. Termites do not have waists and their body parts are not as easy to distinguish.

Here is a link you can follow that will help you identify the difference between the two: http://tinyurl.com/p7lpl3w.

You have to be careful when working with pest control companies that do termite exterminations because, unfortunately, they are not always honest. Of course, if these are termites, you must get them exterminated immediately. If they are flying ants, they will be much easier to deal with.

This is a good piece on flying ants from Colorado State University: http://tinyurl.com/owd5l8v.

Q: I have a dwarf lemon tree with many yellow leaves. Can I add iron at this time of year?

A: If you do any iron applications it would be best done as a foliar spray rather than applied to the soil. If the yellowing is not extensive you could wait until spring.

If you want to do it now, use an iron chelate as a liquid application, add about 1 tablespoon of white vinegar to tap water and then add the appropriate amount of iron chelate. You should add a wetting agent to help the spray penetrate the leaves.

You can make this by using a liquid detergent such as Dawn or Ivory at a rate of about 2 teaspoons per gallon added to the finished spray mix. You would apply this to the leaves immediately until the point where it begins to run off the surface. Let the leaves dry and repeat it again.

You will have to make foliar applications four or five times to get much results from liquids applied to leaves of citrus. Each time you will have to adjust the alkalinity of the water with vinegar and add a wetting agent such as the liquid detergent.

The foliar sprays should always be freshly made and applied immediately. Unfortunately iron liquids do not store very well when they are homemade.

It might be cheaper to buy the liquid already made and make the application.Commercial sprays will hold their iron much longer than homemade iron sprays because they have adjusted the chemistry of the solution better than you can at home.

It also is possible it could be a magnesium or manganese problem because they can create yellow leaves.

Q: Why are the tips of my Yucca rostrata leaves turning brown?

A: This is pretty common on Yucca unless they are grown in filtered sunlight. They always tend to have brown tips.

Yours looks a little excessive though. When we have brown tips on foliage of desert plants it usually means they are getting too much water, not getting enough water or there could be accumulated salts.

Let’s think about this plant a little bit. Yucca rostrata is native to the Chihuahuan desert so infrequent irrigation is critical to its health.

The best way to determine what is going on is to ask yourself how often you are watering. It doesn’t need to be watered that often, so if you are watering more than every two or three weeks in midsummer, I would suggest this is too often.

If this plant is on the same irrigation circuit as other landscape plants and these other plants are not desert plants, then I would suggest it might be watered too often.

The volume of water you give the plant is not as critical as the frequency. In other words you can give it a large volume of water and not hurt the plant as long as you wait long enough before the next irrigation. Giving it a large volume of water may waste water but it seldom keeps the soil too moist between irrigations.

If this plant is on an irrigation circuit where it is getting watered too often, take it off of that irrigation circuit and water it by hand every few weeks. It will like a couple of deep winter irrigations, a spring irrigation, a midsummer irrigation and a fall irrigation and that’s about it.

If you water it so that the water stays close to the trunk, then the trunk could be rotting. Get frequent irrigations away from the trunk. It is OK to water it in a large basin beneath it if it is done infrequently.

If there are other plants around it, it is probably getting enough water from its neighbors. But I would still give it an occasional drink to be on the safe side.

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.