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Sunday, February 22, 2015

How to Correct a Bad Haircut on Rosemary

Q. I have a rosemary bush in the front yard that's very healthy but has grown quite big in the seven years since it was planted. Is there a technique to trimming? I tried once before and it looked like a really bad haircut.

A. Rosemary can be quite dense in its interior if it is watered and fertilized normally. It becomes denser if it is pruned with a hedge shears. If rosemary is very dense, very little light penetrates inside the canopy. This lack of interior light causes leaf drop resulting in an interior that is only wood.

Pruning with a hedge shears results in a surface layer of green foliage only an inch or two deep. This surface layer of green foliage is new growth which has been sheared. If left draped over a wall, the new growth may be several inches long.

Dramatic pruning of an older plant can result in that “bad haircut” you mention that reveals its woody interior. The only portion that can be removed safely without causing a “bad haircut” is a small portion of the green surface layer.

Rosemary will regrow once it has a bad haircut but it takes time and you and others are forced to look at the bad haircut until it grows back during warm weather. Any extensive pruning of rosemary that can result in a bad haircut should be delayed until warm weather.

You have two options. The first is to go ahead and give it a bad haircut beginning in about April knowing full well will take time to recover. The second is to remove older plants and replace them with younger plants that you can begin to shape at an early age.

Once pruning has been initiated with a hedge shears, the shape of the plant is difficult to correct. If you wanted to be an ornamental rosemary is one of the easiest plants to prune. It adheres to any shape you want to give it.

At Christmas time rosemary is available in nurseries in many stores shaped into 3 to 4 foot tall Christmas trees. I've seen it planted around trees and the shrub is carved out around the trunk. I've seen it planted in a raised planter and cut off along the wall like bangs of the haircut.

I prefer a more normal look which used to reach deep inside the plant and remove older wood. Every time you make a cut, it is hidden by the growth that's remaining. If you prune like this, it will never look like you even touched it except it smaller.

Look for the growth that is longest, follow the stem back inside the canopy of the plant to a place where there is side growth or side branch. Cut just above this side branch so the side branch can continue to grow but you are removing the longer stem.

Usually you would do this in three or four locations. Depending on how restrained you want the rosemary to be, you might do it annually or every 2 to 3 years.

Prostrate rosemary in natural form in rock landscape

Companion Planting Successes Can Be Variable

Q. I am looking for a spring companion list for Las Vegas. I have an easy to read chart for fall in order to know where to put different plants and which ones don't like to be next to each other but can’t find the same resource for spring.

A. The topic of companion planting is very large and has a lot of good information but unfortunately it also has a lot of folklore that is either regional in nature or lacks validation.

Companion planting can focus on the inter-planting of crops, the use of understory crops, the planting of trap crops, suppression of pests by other plants, planting to increase the levels of predators, and more.

For the general public, the term has evolved into the planting of crops for mutual benefit. These companion plants are sometimes referred to as “friends” to other crops without getting into much detail.

There is good evidence for the planting of trap crops for aphids, whiteflies, nematodes and a few other pests. I have heard anecdotal evidence for the use of plants like garlic for repelling certain types of insects or even rabbits. Some people will swear by it and other people who have tried it may say it doesn't work.

This opens another set of problems because in some cases it may work and in other cases it may not which causes confusion. I have tried to maintain neutrality on these issues and recommend situations where I am comfortable there is solid scientific research to support it or not support it. People are free to post their suggestions on my blog and I will publish them provided they are commercial neutral.

Where I am comfortable recommending companion plants are in the areas of trap cropping, inter-cropping and the planting of understory plants. There are some very good evidence that interplanting of crops can have some big benefits including a reduction of pest problems compared to large-scale monoculture where only one crop is grown.

Without getting into detail, there are areas I am very uncomfortable making recommendations because there is contradictory information or the research flatly does not support it.

For people like yourself who want to experiment in these areas, I strongly support it and test it for yourself. No one can dispute it if it works for you. There are publications that do support this kind of gardening activity such as

Other sources you may be familiar with include MotherEarth News, Old Farmer's Almanac, and many others.They are fun to read!

A balanced assessment of companion planting was done by Cornell and can be found at http://www.gardening.cornell.edu/factsheets/ecogardening/complant.html 

How to Prune Arizona Rosewood Against a Wall

Q. I planted a 5 gallon Arizona Rosewood a year ago against a wall for visual screening. How and when should I prune it?
Arizona Rosewood one year after planting
A. This plant can be grown as a shrub or small tree. As a shrub, led it continue to grow as it is except for any weak stems. Any weak, floppy stems should be cut back about 1/3 to half their length to encourage them to become stronger.
As a tree, it can be grown with a single trunk or multiple trunks. This initial pruning to establish its architecture or form should be done during the winter or early spring. It is not too late now.
If your plan is to use this as a small tree, then I would select 3 or 5 larger diameter stems (an odd number is more pleasing to the eye) coming from the ground and eliminate all other growth coming from the base. As new growth appears from the base, eliminate it at any time of the year you see it.
Next, stake these stems individually in an arrangement you would like them to grow. Staking young stems for one year will encourage them to continue growing in those directions. Finally, cut any long, floppy stems back to encourage strength. Make these cuts ¼ inch above a side branch in any direction away from the wall. Remove any strong growth growing towards the wall.
Here is some excellent information with more background on Arizona Rosewood by an extension agent in Arizona.

Why Are My Leaves Yellowing on Loquat?

Q. The leaves closest to the trunk of my two-year-old loquat have started turning yellow and falling off. New leaves have started to grow and they look fine. It was a 5 gal tree when I planted it. Last year the tree grew very well and produced a few loquats.This year the amount of fruit appears to have doubled but it has developed this leaf problem. 
I did some research on loquat leaves turning yellow. They suggested overwatering might be the problem.  I give it about 24 gals of water once a week. I checked the soil with a moisture meter and it does not show being wet.

A. I cannot give you any definite answers why your loquat has initiated leaf drop and yellowing of the leaves. I can tell you this; many leaves will yellow just before they drop from the tree so this type of yellowing just means that the leaves have died and will drop soon. The leaf color of loquat without chlorophyll is yellow.
When the tree has initiated the dropping of its leaves, the leaves will lose their chlorophyll and hence their green color. The remaining color after the chlorophyll has disappeared will be yellow due to the presence of carotenoid pigments which are masked by the presence of green chlorophyll.
Most likely this tree went through some sort of shock. This shock initiated leaf drop. The shock can be related to water, salts including salts from fertilizers, a light freeze, toxic chemicals or salts such as a high concentration of fertilizer applied to the leaves, etc.
The water-related problem can be from too much or not enough. For instance, if it went through a very dry spell it will drop its leaves. If the soil is too wet for an extended period, it will drop its leaves. If fertilizer was applied to close to the trunk or the rate was too high for the plant, it will drop its leaves.
There are two types of overwatering; one is related to the volume of water the plant is given while the other one relates to how frequently the water is applied. The overwatering I am talking about is applying water too often, not overwatering due to applying too much water in a single application. Once a week is not too often in my opinion unless you have a drainage problem.
If you do not think the soil has been too wet or you have not fertilized the tree by either applying fertilizer to the soil or spraying leaves, then I would just wait and see what happens.

If you applied fertilizer to the soil and you suspect the application was too strong, then flood the area with water and push the salts through the soils and away from the trunk and past the roots. That's probably the best I can do without more information.