Relying on Lawn Water to Water Trees and Shrubs a Waste of Water

Q. I have a patch of grass in my back yard and I would like to put plants, shrubs and flowers around the perimeter. Can you tell me what type of plants to put since they will be getting their water from the sprinklers?  I follow the watering schedule for my area and during the summer months there will be a lot of water so I would need to know what plants and shrubs like a lot of water.

A. This is not how we should be thinking of watering in the desert. Plants that grow on the perimeter of a lawn survive because of the over irrigation of the lawn. If we give the lawn precisely the amount of water which it needs, there will be very little water left for plants growing along the perimeter of it.

This Siberian elm has died back because it was surrounded
by grass and now was replaced with desert landscape
and rock mulch

            Lawns should be irrigated so that the water supplied to them is adequate and no more. Plants growing along the perimeter of a lawn should be watered so that they get precisely enough water as well. This would require that these perimeter plants be irrigated with their own irrigation system, not with water coming from the lawn.

            Lawns are watered frequently and with small volumes of water because of their shallow root system. Other shallow rooted plants, like annual flowers and vegetables, are watered in the same manner and require the same frequency of irrigation.

            Deeply rooted trees and shrubs are watered less often but with a higher volume of water so that their entire root system is wetted when the irrigation has been completed.

Winter Cold Limiting Factor for Citrus in the Mojave

Q. I have read your blog extensively.  I really like that you have stuff on there month to month so I know what to watch out for. Inspired by you, I have planted a tree from your recommended tree list and another that I don't think is in there, a Meyer lemon. I planted a lemon after seeing other people in the valley having success with it. I would like to know what precautions I should take growing a lemon tree here.

The orange tree died back and the sour orange rootstock
took over. Notice there is no trunk left on this tree.

A. I have not included citrus on my list because it is too cold at the Orchard in North Las Vegas to grow citrus. However, there are numerous microclimates in backyards that will support citrus in the Las Vegas Valley. It is not a crop to be grown commercially here but you certainly can grow a few here and there including some of the more tender types of citrus.

            We have very few citrus problems here. The biggest problem is winter cold and freezing or dieback. Fertilize citrus just as you would any of the other fruit trees. Allow lemon fruits to mature into late November and December and then pick them. You should be getting the fruit off of the tree no later than early January as this may interrupt production for the coming year if you don't.

Lemon Tree Has One Major Problem in the Mojave Desert

Q. I have read your blog extensively.  I really like that you have stuff on there month to month so I know what to watch out for. Inspired by you, I have planted a tree from your recommended tree list and another that I don't think is in there, a Meyer lemon. I planted a lemon after seeing other people in the valley having success with it. I would like to know what precautions I should take growing a lemon tree here.

Sweet orange died back and the rootstock, sour orange,
took over. The indicator is no trunk left and sour fruit.

A. I have not included citrus on my list because it is too cold at the Orchard in North Las Vegas to grow citrus. However, there are numerous microclimates in backyards that will support citrus in the Las Vegas Valley. It is not a crop to be grown commercially here but you certainly can grow a few here and there including some of the more tender types of citrus.

            We have very few citrus problems here. The biggest problem is winter cold and freezing or dieback. Fertilize citrus just as you would any of the other fruit trees. Allow lemon fruits to mature into late November and December and then pick them. You should be getting the fruit off of the tree no later than early January as this may interrupt production for the coming year if you don't.

Don’t Confuse Borers in Fruit Trees or the Result Could Be Lethal

Q. Concerning my peach tree, it looks like the peach tree borer is my most significant pest. Being that the Bt pesticide spray is a great organic preventative and killer of the borer, and I already have it and use it in my vegetable garden, shall I just spray the peach tree once a week as a preventative? If I do, how long do I keep this up until the threat is over? Are there any other insects to worry about such as aphids?

A. There are two different borers which we must be careful not to confuse. Control is entirely different between these two borers. The borer you refer to damages the trunk and limbs of many trees including fruit trees as well as ornamentals. This borer is very difficult to control with pesticides.

Flatheaded borer (probably either Pacific flatheaded borer
or Flatheaded apple tree borer) that causes limb dieback

            Bt, an organic spray made of a bacterium, will not kill these deadly borers which we see as damage and dieback of limbs and entire trees. Bt sprays will, however, kill a borer which causes wormy peaches, nectarines and apricots. This borer is called the peach twig borer.

            Peach twig borer kills the soft, succulent growth of peaches and nectarines at the beginning of the growing season. We should start seeing this damage right now. Its lifecycle is very short and so the population of this pest builds very quickly to enormous numbers in a matter of a few months.

Peach twig borer larva or immature form (striped) in the
flesh of peach in upper right hand corner of the picture
causes wormy peaches, nectarines, apricots, almonds

            As peach, nectarine and apricot fruit matures and gets close to harvest, the attacks from this pest switch from soft, succulent growth to soft succulent fruit. These new attacks result in wormy peaches, nectarines and apricots. Instead of shoots which dieback, the fruit becomes infested instead.

            The trick is to get this pest under control as early in the season as possible to prevent this pest’s population from exploding in numbers. We use sprays such as Bt or Spinosad early in the season, starting now, to help keep these populations small and under control.

            I usually apply one of these chemicals when I start to see a few new shoots of peach and nectarine begin to die back. We call this flagging. We also use special traps which catch and monitor this insect when it is hatching and flying. You will see pictures of this on my blog.

Flagging from peach twig borer

            This flagging is one indicator that you need to get out there and start spraying to knock their numbers down and protect the fruit.

            Unfortunately there is not much that you can do to prevent the more damaging borer, a beetle in its mature form, from laying its eggs on the upper surfaces of sunburned branches. These insect eggs hatch and the larvae penetrate the tree through its bark causing extreme damage to the limbs by tunneling just under their surface.

            The peach twig borer adult on the other hand is a moth and its immature form is also a larva but resembling what we might call a “worm” in appearance. The BT sprays do not work on insects which are in the beetle family, only those whose adults are moths.

            Aphids are not a big problem on peach like they can be on plums and plum relatives like pluots. Aphids like cool weather and begin to disappear when it gets hot. Their damage is usually cupped or distorted leaves which are frequently sticky due to feeding by the aphids.

            Because the aphid season is short in our climate, they are usually not worth controlling unless we have a prolonged cool spring.

You Don’t Fertilize Trees the Same Each Year

Q. Do I fertilize my peach tree even though it looks like it's doing great? If so, what type of fertilizer and concentration would you use and how often?

A. You adjust your fertilizer application according to how the tree is growing. If your tree is growing well, then reduce the amount you apply but do not eliminate your fertilizer application.

            If the growth is lush, then cut way back on the amount of fertilizer that you apply. If you're growth is skimpy, then increase the amount of fertilizer that you apply. By cutting back I would reduce it by half. If you're increasing the fertilizer, then increase it by half the amount.

            You can increase the amount of fertilizer you give a tree by increasing the amount you give it in a single application or, a much better approach, apply it more often in smaller amounts. You can accomplish the same thing by switching to slow release fertilizers. They are more expensive but they release fertilizer more slowly over time and so require only one application each year.

            Begin fertilizer applications in late January and continue them into July if you want to but use very small amounts of fertilizer at each application. You can apply fertilizer as a single application in late January and not fertilize again for the rest of the year if you want to. That will also work. Do not skip your iron applications regardless of your other fertilizer application.

Fertilizer Amount for Fruit Trees Depends on How It Is Growing Now

Q. Do I fertilize my peach tree even though it looks like it's doing great? If so, what type of fertilizer and concentration would you use and how often?

Peach tree with this much new growth will require
less than half the fertilizer that was applied last time

A. You adjust your fertilizer application according to how the tree is growing. If your tree is growing well, then reduce the amount you apply but do not eliminate your fertilizer application.

            If the growth is lush, then cut way back on the amount of fertilizer that you apply. If you're growth is skimpy, then increase the amount of fertilizer that you apply. By cutting back I would reduce it by half. If you're increasing the fertilizer, then increase it by half the amount.

I would use a fertilizer specifically formulated for fruit trees. If you do not know how to choose a fertilizer then this is the safest way to select one.

            You can increase the amount of fertilizer you give a tree by increasing the amount you give it in a single application or, a much better approach, apply it more often in smaller amounts. You can accomplish the same thing by switching to slow release fertilizers. They are more expensive but they release fertilizer more slowly over time and so require only one application each year.

            Begin fertilizer applications in late January and continue them into July if you want to but use very small amounts of fertilizer at each application. You can apply fertilizer as a single application in late January and not fertilize again for the rest of the year if you want to. That will also work. Do not skip your iron applications regardless of your other fertilizer applications.

Dont Confuse Borers in Peaches

Q. Concerning my peach tree, it looks like the peach tree borer is my most significant pest. Being that the Bt pesticide spray is a great organic preventative and killer of the borer, and I already have it and use it in my vegetable garden, shall I just spray the peach tree once a week as a preventative? If I do, how long do I keep this up until the threat is over? Are there any other insects to worry about such as aphids?

Branch dieback due to the borer that gets in the tops of
sunburned branches. No real pesticide available for
keeping this pest out. Whitewash and don't overprune
the canopy.

A. There are two different borers which we must be careful not to confuse. Control is entirely different between these two borers. The borer you refer to damages the trunk and limbs of many trees including fruit trees as well as ornamentals. This borer is very difficult to control with pesticides.

            Bt, an organic spray made of a bacterium, will not kill these deadly borers which we see as damage and dieback of limbs and entire trees. Bt sprays will, however, kill a borer which causes wormy peaches, nectarines and apricots. This borer is called the peach twig borer.

            Peach twig borer kills the soft, succulent growth of peaches and nectarines at the beginning of the growing season. We should start seeing this damage right now. Its lifecycle is very short and so the population of this pest builds very quickly to enormous numbers in a matter of a few months.

Flagging or new growth dieback due to peach twig borer

on almond. The look is the same on peach or nectarine.

            As peach, nectarine and apricot fruit matures and gets close to harvest, the attacks from this pest switch from soft, succulent growth to soft succulent fruit. These new attacks result in wormy peaches, nectarines and apricots. Instead of shoots which dieback, the fruit becomes infested instead.

            The trick is to get this pest under control as early in the season as possible to prevent this pest’s population from exploding in numbers. We use sprays such as Bt or Spinosad early in the season, starting now, to help keep these populations small and under control.

            I usually apply one of these chemicals when I start to see a few new shoots of peach and nectarine begin to die back. We call this flagging. We also use special traps which catch and monitor this insect when it is hatching and flying. You will see pictures of this on my blog.

            This flagging is one indicator that you need to get out there and start spraying to knock their numbers down and protect the fruit.

One type of pheremone trap used for trapping
peach twig borer

            Unfortunately there is not much that you can do to prevent the more damaging borer, a beetle in its mature form, from laying its eggs on the upper surfaces of sunburned branches. These insect eggs hatch and the larvae penetrate the tree through its bark causing extreme damage to the limbs by tunneling just under their surface.

            The peach twig borer adult on the other hand is a moth and its immature form is also a larva but resembling what we might call a “worm” in appearance. The BT sprays do not work on insects which are in the beetle family, only those whose adults are moths.

            Aphids are not a big problem on peach like they can be on plums and plum relatives like pluots. Aphids like cool weather and begin to disappear when it gets hot. Their damage is usually cupped or distorted leaves which are frequently sticky due to feeding by the aphids.

            Because the aphid season is short in our climate, they are usually not worth controlling unless we have a prolonged cool spring.