Rootstock may be source of sour fruit

If you want to know everything about roses in the desert, here is your chance. The Las Vegas Valley Rose Society will hold its annual rose pruning workshop Saturday from 9a.m.-2 p.m. at 1112 Oak Tree Lane. Oak Tree Lane is near the intersection of North Valley View Boulevard and West Washington Avenue. It is open to the public and is free. These are the rose experts in the Mojave Desert.

The University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas is shifting gears and will talk about fertilizers and pest control on fruit trees Saturday from 9 a.m.-noon with yours truly. On Sunday I will be at Plant World Nursery from noon to 2 p.m. covering my top picks of recommended fruit trees for Southern Nevada and why. Download my list from my blog and bring paper and pencil to take notes. Or email me and I will send it to you.

Q: I have a dwarf tangerine in a container that gives lots of fruit but it is sour. Why?

A: Sugar content is developed over time as fruit matures. When the fruit is immature it usually has higher acidity and low sugar content. As the fruit matures the acidity drops and sugar content climbs. Be sure to wait for full color development in the fruit and it should be at its highest sugar content.

Tangerine is sometimes grafted onto sour orange rootstock. If the tangerine part of the plant dies, the sour orange rootstock will replace it producing beautiful, but very sour fruit; it will never become sweet. If this is the case, and this happens a lot in Las Vegas due to our winter freezes, dig it out and replace it.

Q: My privet hedges turned a copper brown color. I have three in a row on one side that are really brown while the hedge on the far right still has a substantial amount of green but it is starting to get spots. I'm not sure what to do to save them. Pictures are attached.

A: These pictures look like possible cold damage. It could be something else, but I want you to do this to find out. Walk over to the privets and start bending some branches just below where they were pruned. If they are still soft, supple and bend easily without breaking, then it is most likely cold damage that caused leaf death.

If they are supple and bend, don't do anything. They will leaf out again this spring as temperatures begin to warm, or you may see them leaf out sooner than that.

If they all are snapping when you bend them, then there is severe dieback. It is still possible the dieback is due to cold weather this past November. Cold temperatures are very damaging during the early winter if the plants were caught unexpectedly by sudden drops in temperature.

There was really nothing that you could have done to prevent this. It is the luck of the draw sometimes. However, if there was severe dieback you should have healthy stems closer to the ground. I would wait until late February or March and see where the new growth comes from. I would then cut the dead growth slightly below this new growth.

Make sure they were getting water this winter. Turn your station on and look for water coming out of your irrigation emitters. If there was blockage and you didn't notice, it's possible they could die back from a lack of water. My best hunch, however, is cold damage.

Q: I have a large pot of sage growing on the protected (north) side of my house where all my citrus and other herbs have done well. I notice that when the weather cools, the sage leaves turn a whitish color. I collected some for sage dressing, but I didn't bother using the white leaves, just the green ones. Is this a natural occurrence during cold weather? Would those leaves have been OK to use?

I dry the good leaves in the oven at 225 degrees Fahrenheit for about one hour, leave them out in the house to get thoroughly dry for a day or so, then crush them in a coffee grinder. This works great for my use in the kitchen, especially for sage dressing.

A: This white discoloration is probably some damage to the leaves due to cold. You are right; don't use them.

However, drying at 225 F is far too high. This should be done at temperatures between 95 and about 125 F. There is a lot of damage done to the herbs at high temperatures, particularly above 140 F.

Our weather and climate is perfect for drying herbs without the use of extra heat. It will take longer than one hour but the quality will be much better. Cut the stems of those with flower buds just starting to form. Hang these bunches in the open air and not in intense sunlight for one week to dry.

If this is too slow for you, use a cookie sheet and put in the oven at the lowest temperature that provides heat. Bottom line, do not use excessive heat and keep them out of intense sunlight while drying. I hope this helps.

Q: I have a single, 4-year-old pomegranate tree in Las Vegas. The tree produced excellent fruit the first three years. This year the fruit was spoiled as it came off the tree. The tree appeared normal. Looking at the fruit, it wasn't evident if it was infested with a bug or a disease. Would you have any suggestions on what caused it?

A: The most likely reason would be an insect called the leaffooted plant bug. They will infest pomegranates, almonds and pistachios most frequently. Their feeding can cause small holes in the outside of the fruit or nut.

This wound can open the fruit for infection by disease and possibly cause a nut not to develop inside the shell, causing what we called blanks to develop. You will see these insects overwintering on your fruit trees or nearby landscape trees as well.

These are nefarious denizens of the worst kind and seem to have no value except to breed more of the same. I would recommend spraying your fruit and nut trees with dormant oil twice during the winter and follow this a few days later with an insecticidal soap.

I have seen most of these adults wintering on the stems and trunks of trees, usually in the sunlight because of the heat they can get. I hope this helps.

Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at xtremehorticulture.blogspot.com.