Windbreak should prevent bloom loss

Q: For the last two years in North Las Vegas heavy winds have come while my young peach tree was in bloom. Both years I wrapped it as best as I could but the blooms were blown off the tree anyway. Do you have a good way to protect the tree during these windy times? Do you wrap your trees at the farm?

A: We don't wrap our trees and we are exposed to strong, cold winds from the northwest with recorded gusts of 70 mph.

My guess is that the wind is channeling through that area, which will increase its speed. I would suggest constructing a windbreak to protect that small area by diverting or slowing the wind. This can be made from fencing or evergreen plants.

You do not need to stop the wind entirely, but you can slow it down. Windbreaks should not be a 100 percent barrier but allow about 20 percent of the wind to penetrate through it. Things like chain-link fences with PVC slats or woven materials placed along the windward side of the fence will affect wind a distance of five to eight times the height of the barrier.

Wind will increase its speed if it goes from a large area through a small area, such as between homes or into backyards. This can be a problem if the channeled wind enters small areas where fruit trees and vegetable gardens are located.

Be creative. See if you can design a windbreak into your existing landscape that can help modify that part of your yard and make it more enjoyable.

Q: You have always have stated to prune shrubs and trees when they are dormant, but it seems mine do not go dormant in the winter. They continue to grow even though they get water only once a week. I halved the fertilizer application but they continue to grow larger than I want them to. Why do they grow when they should be dormant and when should I prune them to slow their growth and spread?

A: Shrubs' nature is to continue growing until they reach their mature size. Keeping them smaller than this will require more maintenance than selecting one that is the size you need. Select shrubs by determining the size you need and finding one that is that size at maturity.

Dormancy here is not the same as dormancy in Minnesota. Dormancy here, in some cases, means plants may stop growing as much, not that they stop growing at all. It just depends on the plant .

Where the plant is located in the landscape also dictates its level of dormancy. Very warm microclimates in the yard may mean that some plants never totally shut down during the winter while in colder spots they do. Hot south- and west-facing walls with little winter wind are the warmest locations.

Cutting back on water and fertilizer will help but they do not act like an on and off switch for plants. Think of fertilizer and water like a rheostat that can increase and decrease growth but not totally shut it down. At some point though, turning down the water and fertilizer will damage the plant.

Focus your pruning on older growth and remove it from deep inside the canopy, leaving the younger growth still flourishing. Prune in the winter months. Avoid trimming on the edge of the canopy whenever you can. Hide your cuts if at all possible. They should not be obvious. This will help keep them smaller.

Q: I have a rock garden that is 10 years old. We have fabric under the rocks to prevent weeds, but I seem to have more weeds each year. Could you recommend any effective pre-emergent herbicides?

A: This will sometimes happen for a couple of reasons. These fabrics degrade over time and some last longer than others. Those with a tighter mesh usually last longer than those with an open or woven mesh. Landscape fabrics should be overlapped so there are no gaps when they are installed. I am assuming you did all of that.

There are some weeds they just don't prevent, such as Bermuda grass and nutsedges or nutgrass. The key to controlling these is to remove them as soon as you see them . Don't let them get older as they just get stronger and more difficult to control.

Over time, dirt and dust accumulate in the rocks on top of the fabric and provide a place for weeds to grow. Some rock mulches, like decomposed granite or sandstone, degrade over time. Sandstone is the worst. As these break down and decompose, they leave debris on top of the landscape fabric. This is a place where weed seeds can germinate.

Don't let weeds get to the point where they flower and produce seeds. The seeds spread all over the place. I always look at chemicals as a last resort. If you can spend a few minutes once a week just pulling weeds, 95 percent of the weeds that you see will pull easily. It is easier if you pull them just after an irrigation.

In the same way, 95 percent of the weeds are most likely annuals. If you can kill the tops before they flower, this will reduce the weed population tremendously. There are sprays that will "burn" the tops down and thus prevent flowering and consequently seeds.

When we start talking about weed killers, we have to pair the herbicide with the weeds we want to kill. If we pair the wrong weed killer with a weed, it won't work and we blame the weed killer. So it is very important to know what weeds you are trying to fight.

However, there are a few weed killers that can kill a wide range of weeds, but not all of them. Pre-emergent weed killers, aka pre-emergent herbicides, include a variety of products . Some of the lesser-known brands have the same ingredients as more expensive products but are not marketed as well.

The pre-emergent products you can get from your local nursery or supplier are going to be general, all-purpose pre-emergent herbicides. One product by Monterey is called Impede. It contains surflan, which is a very good pre-emergent herbicide .

Other ingredients you can look for that control a wide range of weeds are dacthal, ronstar, goal and treflan.

Be sure to read the directions and follow them precisely.

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