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Monday, March 19, 2012

Pistachio Pollination and Pruning to Keep it Smaller

I will add some photos next week.

Q. My husband asked me to contact you about how to trim our pistachio nut tree and how to get it pollenated.

A. You can still do some light pruning on fruit and nut trees. On pruning your pistachio I would cut back the new growth to about 18 inches above where you see the spurs growing. If this is too severe, then I would just cut back last year’s growth so that it is only about 12 to 18 inches long.      

Pistachios come as both male and female trees (Peters is the male; Kerman is the female). You will need a male tree somewhere close by since they are wind pollinated. The male and female may be planted in the same hole, about 18 to 24 inches apart, but the male tree is more vigorous and will have to be cut back harder than the female to keep it under control.

            If planting in the same hole and you should put a male tree on the north side so that the female, the less vigorous of the two, receives more sunlight. Otherwise you will have to rely on a male tree from a close neighbor or plant your own.

Almond Nut Drop and When to Spray an Insecticide

Leaffooted plant bug on pomegranate with babies (nymphs)
Q. Several months ago you answered my question as to what was affecting the loss of all my almonds in my almond trees. You said I should apply the insecticide Sevin for pest control. But when do I apply the Sevin? My almonds are doing well now but they always do well now and then later I see something ozzing out of the nuts and a yellowish design on the inside. Then the nuts drop from the tree. So when do I spray with this insecticide?

A. If I told you to apply Sevin insecticide I must have thought you had leaf footed plant bug in your almonds. My personal philosophy is to use pesticides as a last resort for insect control whenever possible. This would be the only reason I would recommend the use of a pesticide in almonds.

            You would apply it when you see the insect present on the leaves. This insect has overwintered in yours or your neighbors landscape plants. I have seen them overwinter in our climate in these locations. When leaves emerge, this insect will begin feeding and laying eggs.    The first thing you will see are herds of the immature called nymphs on the undersides of leaves. You might see some adults as well but the babies are much more numerous. You should start to see them around late April or early May so start looking then. When you see them, begin spraying immediately according to the label mixing rate. Wear protective clothing.

Putting Rock Mulch on Top of Composted Soil/Wood Mulch for Fruit Trees

Q. In my backyard in 2010 I planted a semi-dwarf Early Elberta Peach tree and a Katy Apricot.  I hand-watered them and left their tree wells uncovered until I completed the irrigation system around April 2011.  Now each tree has drip emitters. I put a thick layer of Dr. Q's Pay Dirt potting soil on top of each tree well and then covered the potting soil over with a layer of the ruby red stone that I have throughout the floor of my backyard.  Both trees are doing very well and I want to be sure to do everything I can for their long-term health.

            Per your View article, should I move the red stone back off the top of the tree wells to a radius of 6 feet away from each tree, and then cover each tree well with a layer of wood mulch instead?

 A. One soil problem we have when growing fruit trees in our desert is the small amount of organic matter in our soils. This miniscule amount of organic matter is not enough for nearly all plants including so-called desert plants.

            Fruit trees, and nearly all other plants, perform much better in our soils if organic matter (compost preferably) is added to the soil surrounding the roots. I hope that you added a lot of amendments to the soil at the time of planting, not just the surface.

            I have compared two application methods when compost is applied to fruit trees: mixing it only to the soil at the time of planting and adding it only to the soil surface after planting. Adding it to the soil, not just the soil surface, dramatically improves plant growth in our desert soils.

            The best soil amendments to use to use when increasing organic matter in our soils are homemade composts. Commercially made composts, available in bags or bulk and extremely variable in quality, would be next. The good ones (there are good ones out there now thanks to the explosion in organic gardening) are expensive. The cost of enough good quality compost, added to the hole at planting time, in some cases might rival the cost of the plant itself.

            If trees are planted in amended soils and then the soil surface covered with rock, over time, the organic matter in the soil is “used up” so to speak by soil microorganisms. When the majority has been used up, we say the soil has become “mineralized”. Without addition of organic matter to the soil surface every two to three years, the soil slowly reverts back to its previous desert condition.

            From my observations of fruit trees and nondesert landscape plants growing in our desert soils amended only at the time of planting and mulched with rock only, the soil is typically “mineralized” by the fourth or fifth years. Cacti and desert plants are much more tolerant of mineralized soils but still grow better in amended soils.

            By placing wood mulch on the soil surface where the soil is wet, it slowly decomposes. Through its decomposition it adds organic matter to the soil. Through their decomposition, mulches add a lot of organic activity such as beneficial microorganisms and earthworms leading to improved plant health. Rock mulch cannot add organic matter and so in a few years none of the benefits of organic mulches will be present.

            I am guessing your trees will be fine for several years with rock mulch covering the soil surface. But what may happen in the fourth through the sixth years, as the soil becomes mineralized, is that they may begin to decline in health.  The trees may become more and more yellow, leading to leaf scorch, followed by branch dieback and insect attacks such as borers.

            Borers come into play due to a decline in tree health. Decreased plant health causes a thinning of the tree canopy leading to an increased amount of sunburn damage to the limbs. Sunburn damaged areas are the ideal locations for borers damage to occur.

            My concern would be how you might add organic matter to the wet soil surfaces as it decomposes. If you can do this then it will probably not be a problem.  It is best for the trees if you can put wood mulch in the wetted area under the trees. In the drier areas under the tree the wood mulch will not decompose.

Lower Limbs of Fruit Trees Too High Off of the Ground

Q. I watched your videos on pruning your peach trees for a lateral orchard.  We planted some bare root plums and peach trees last Saturday. I want to do a lateral orchard but there are no branches down at knee level.  They are at about hip level.  Would I still cut the trunk off at knee level?  Would branches or buds form down lower if I did that or would it just kill my trees?

A. It should be a ladderless Orchard since what we are trying to accomplish is to keep the trees close enough to the ground that we don't have to use ladders for pruning or harvesting the fruit. I could see how listening to the word ladderless on a video might be heard as lateral.

            If a peach or plum has been in the ground for a while, I would not recommend cutting the trunk at knee height. You will run the risk of severely damaging or even killing the tree. It depends on the tree but with plum or peach it would be very risky to cut an older part of the tree to reestablish the scaffold limbs. Now, if your tree was an almond then you could cut larger diameter wood and it will regrow below the cut. 

            You will have to work with the tree structure that you have. Maybe you will not be able to keep it at 6 1/2 to 7 feet tall but you certainly could keep it under 10 feet tall and still have a sizable harvest. My videos are available on Youtube by searching for Extremehort. I will be posting some new ones next week.