Factors to keep in mind when choosing trees
Q: Which should I pick for growing here: persimmon, Persian mulberry, walnut or pecan?
A: Each has its strengths and weaknesses. Of the four, the one that handles the heat the worst is persimmon. Persimmon should be grown with afternoon shade such as the east or north side of your home. You also have to do some special pruning, heading back second-year small limbs, to get it to work in the desert.
Walnut and pecan are big trees, and they require a lot of water. Of the four that you selected, pecan is the tallest at maturity, averaging 80 to 100 feet tall. Walnut is next, at about 50 to 60 feet tall. They’re probably not a good fit for most yards. Maybe you can grow one of these trees in a small yard, but you will pay dearly in water cost.
The Persian mulberry is the smallest of those three at 25 to 30 feet tall.
The biggest challenge of the last three is growing and harvesting the fruit. To harvest the fruit as low on the tree as possible, I would suggest growing the Persian mulberry as a bush rather than a tree and keeping it below 10 feet tall. Otherwise, the birds will get fruit you can’t reach.
By the way, all the purple mulberries stain cement, cars and other things left out in the open. White mulberries stain less.
Q: Is there a method to supercharge the growth of a Swan Hill olive tree? Maybe a blend of nutrients and methodical watering?
A: About the fastest growth I have seen from trees is when I grew them hydroponically, but that was in a greenhouse. That was for trees that were native to that area: three oaks and three maple trees. They had a greenhouse, access to nutrients, water and air whenever needed. The next-fastest growth was outside using a fertilizer injector. But that is the key: roots having access to nutrients, water and air whenever they were needed and being able to use them whenever they were needed.
Getting back to your Swan Hill olive tree, I would guess that giving it fertilizer and water whenever needed is the key. I would apply a fertilizer with all of the nutrients about six to eight weeks apart through their growing season. I would make sure they get water to root depth so the water is not a limiting factor. I would make sure that there is at least one day without water during summer months so that the roots have enough air.
Provide fertilizer to this tree every two months starting in mid- to late February and ending when growth is stopped or slowing in the fall, about October or early November.
Q: I have a 5- to 6-year-old dwarf
Meyer lemon tree that is about 10 feet tall and just as wide. It is in the ground and gets lots of sun. It has produced many lemons over the years: last year about 200 lemons, but this year only about 50 and all of them are on one side of the tree facing north. They are all yellow now and I wonder how long I can leave them on the tree before picking them? Also, when is the best time to prune or thin the tree? The center seems to be very dense.
A: After you finish harvesting the fruit (the latest should be February) is the time to prune. Don’t remove the lower branches attached to the trunk (unless they are interfering with each other), and keep shade on the trunk as low as possible. Those branches help protect the tree from direct and damaging sunlight. Remember these are semitropical trees.
If there are branches less than 8 to 12 inches and growing on top of each other, remove the less damaging one at the trunk. In other words, you are just removing the shade created by one of them.
Otherwise, citrus trees don’t need much pruning, just elimination of interfering branches. After the first three years or so give the tree some shape if it needs it. If there are thorns bothering you, remove them. Removing thorns won’t hurt anything.