Q: Can you diagnose what is wrong with my rosemary bush? We have two rosemary bushes which are less than 3 feet apart. One is beautiful, while the other has die-back in the center. The one that has the die-back was replaced last year because the previous one had the same problem. Both of these plants receive the same water and the same fertilizer. When I replaced the rosemary plant last year, I did a 50/50 mix of compost and native soil. I don’t see any pests on either of the plants. Any suggestions?
A: I looked at the pictures. There are no specific pests that would cause this type of damage on rosemary. The most likely culprits would be physical damage to the stems (broken stems) or root rot or collar rot from either planting it too deeply or keeping the soil around the one with dieback too wet.
If the soil was heavily amended with mulch or compost and it was planted in this then it is possible it could have been planted too deeply while the other one was not. Sometimes plants will sink in the planting hole if the soil is too “fluffy” at the time of planting.
This sinking and soil consequently coming in contact with the stem because of follow-up waterings, can cause the main stem or side stems to decay and then entire stems can die back.
I would carefully lift the plant out with a shovel and examine the main stem or trunk and side stems and see if they were planted too deeply. Rosemary is very susceptible to collar rot or keeping the soil too wet. If the stems are rotten, dispose and replant in a new location.
Q: I just saw this video on the Internet on espaliering fruit trees. It is located at http://www.youtube.com/watch?v=MP7voRKFUoE. Is that something that would work well in Las Vegas or just cause more stress to the tree? I have a small area on the south side of my house where the air conditioning unit is and would love to get a green wall of sorts on there to keep our bedrooms from roasting in the summer. I had thought about grapes, but the espaliered fruit trees might be an option.
A: Great video! Yes, John. It will work here. Just keep your water emitters to the outside of the fruit trees and not near the foundation. We have high salts and don’t want to undermine the foundation or walls used for trellising. This will help direct roots away from the structures.
Make sure you whitewash the limbs as they can sunburn in hot, very exposed locations.
I can see you are thinking now in terms of microclimates and growing spaces in the yard. Plants are flexible. Make sure they have enough sunlight to be productive, match the plant to the microclimate and manage the plant to make it fit and make sure you commit the time to doing it. It is that simple.
Q: Ocotillo is the most beautiful plant in Nevada. I have tried twice to grow this and not even one sign of life in five years. Now I’m trying at a different home. I wonder where am I failing?
The soil is mostly poor in Henderson and sandy. I have lots of sun but I avoid western afternoon sun. I also have an area with partial shade. Is this a failure to properly fertilize? Watering? A local nursery indicates I’m doing it correctly but it is a tricky plant. (Now they tell me.)
A: These are tricky plants and not easy to transplant if you are not familiar in dealing with desert plants and cacti. It is also possible to pick up dead plants from the nursery. When they have no growth on them it is very difficult to tell if they are living or not.
One method you can use is the thumbnail method. You can use your thumbnail and scrape a small layer of bark from the stem. It should be green under it and scrape away fairly easily. If it does not, or it is brown under it, then it very well could be dead.
If you want to know if the plant is at all alive, check in several places including near the base closest to where the soil would be and look for green as well. When planting it, make sure it is securely staked into the soil so the roots do not move.
Water around the base of the plant no more frequently than about once every two weeks during the summer. These plants are easily propagated or started as cuttings, stem pieces cut and planted directly into the soil. The trick is not to water so often the stem rots and dies.
I attached a pamphlet on how to establish ocotillo from the Tucson Cactus Society. I am not a big proponent of wetting the canes but the Tucson cactus society is. Readers can see it posted online in my blog next week at Xtremehorticulture of the Desert.
Q. I have nine orange trees on my property and pamper them like my “kids.” One of them (perhaps two) is losing the green color in the leaves although the veins are staying green in color. I would like to send you a couple of leaves for your inspection as I have tried to troubleshoot the problem using the computer and pictures. A local nursery disagrees with my request for manganese sulfate to resolve the problem. Would you send me an address so that I can send a few leaves for your inspection and suggestions?
A. A picture of the leaves will work just as well as sending me a sample. I will be out of the country and so samples will probably not reach me.
Nine times out of 10, a yellowing leaf with green veins, particularly if it is the newer growth at the ends of the branches, is iron chlorosis and not typically manganese or zinc. The manganese sulfate would be used for a manganese deficiency or you could use a manganese chelate.
You can sometimes take an iron solution with a few drops of Ivory liquid detergent and, making sure the iron solution is slightly acidic with a little bit of vinegar, dip the leaves in the solution for a few minutes. You should see a color change in the leaves in about 24 hours or less.
Otherwise you can take some liquid iron chelate with a little bit of detergent like Ivory liquid and spray the leaves three or four times over a period of a couple of days. This will also turn them a darker green if it is iron.
If it is something other than iron, it won’t do anything. Then go ahead and try your manganese application.
If this color change occurred during the winter it is possible it could be cold damage. This appears more like a bronzing of the leaves rather than yellowing. I hope this helps.
Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at xtremehorticulture.blogspot.com.