Mimosa, other trees struggle in rock mulch

Q: I have a mimosa tree and I am giving it a lot of TLC and it seems to do well here.

A: Your mimosa or silk tree looks great and is doing well judging from the picture you sent to me. It looks like it has good growth and a nice dark green color. You must be giving it a lot of attention as it seems to be thriving in rock mulch. I will caution you that these are not long-lived in our climate and tend to suffer a lot of branch dieback or decline as they get older.

They struggle in rock mulch that is fully exposed to summer extremes. They seem to live a bit longer when surrounded by grass . It has never been diagnosed, to my knowledge, but this decline may be mimosa wilt disease, a disease that infects and plugs the tree's vascular or water transporting system.

Continue to keep your tree healthy and it's possible to keep it going for quite a while. If you can keep plants healthy, they can withstand diseases and extremes of temperature and soils better.

Q: What nurseries would you recommend buying fruit trees from (locally or online)? I would be looking to get them in the ground in February or early March, so my only concern with local nurseries would be whether they would have their stock in that early.

A: If you are planting trees that early, you probably will find mostly last year's trees that didn't sell but are usually at some very good prices. Just be careful and buy trees in good shape; don't feel sorry for a tree and think you can nurse it back to health.

Local nurseries usually don't bring new trees in until the weather warms up in late April.

Some of the mass merchandisers will bring in trees early to sell, but be careful of the varieties you select. Some of these mass merchandisers have a good person or two in the gardening department, but many times they do not. I have seen some "innovative" gardening methods at some of these places. And I don't necessarily mean that kindly.

Many times, the mass merchandisers do not look for what grows well here; sometimes you can get lucky and find what you are looking for .

Be careful of rootstocks on apples in particular. You want semidwarfing rootstocks such as M111. The extreme dwarfing rootstocks on apple can be a problem here due to our high light intensities.

There's nothing wrong with fall planting either as long as you can find trees in good shape. Plant in mid-September through October the same way you would at normal times of the year. This is a great time to plant because plants essentially go through two "springs" before they hit the hellish summer weather.

Q: I would like to ask your opinion on a Desert Museum palo verde tree I planted in my front yard here in the Las Vegas area about two years ago. It looks like it is half of a tree with most of its branches on the side sagging toward the ground. It is quite bent over and seems to be getting worse over time. The yard's terrain is slanted, but other trees on similar topography don't seem to have this problem. Do you think it should be staked, limbs removed or the whole tree removed?

A: I see what you're saying from your pictures; the tree is leaning away from the house and does not look perfectly straight up . Personally, I try to visualize what this tree might look like as it gets older.

I frequently find that a tree's character is shaped by its environment and it tends to grow in reaction to that environment. In other words, your tree leaned and grew in that direction because of its location and the impact from surrounding plants and the environment.

As I picture this tree 10 years from now, with this leaning trunk and major scaffold limbs pruned so they are not in the way, it might have a lot of character. This character would be entirely different than the picture-perfect tree you imagined when you bought it.

I would tend to let it go and, as it gets larger, remove or cut back limbs that might damage the house and begin to remove the lower limbs if they interfere with human or vehicle traffic. It will begin to straighten out in the next few years. In my opinion, you have the beginning of a tree with quite a bit of character.

Bob Morris is a horticulture expert living in Las Vegas; he is on special assignment in the Balkh Province, Afghanistan, for the University of California, Davis. Visit his blog at xtremehorticulture.blogspot.com.