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Monday, September 3, 2012

Trees Growing But Lacking Leaves and Not Full

Crepe myrtle lacking leaves
Q. I am one of your long-time readers and fans. I am attaching pictures of four different trees from our backyard in Queensridge (basically Summerlin) that seem to be challenged.  In each case, the tree is definitely alive, but simply lacks enough leaves – or so it seems to us.  All of the trees have received plenty of organic matter, fertilizer (possibly not enough, fish and iron chelate is what they get), water, and all are mulched in with organic mulch (compost under-layer and wood chips on top).  The backyard faces North and West and, as you can see, is quite open as it is surrounded by a golf course.  Why are there so many naked branches, weak-looking leaves, and not enough leaves?  Thank you for your help. 

A. Thank you for the great pictures and breaking them into two emails. That helped quite a bit. Here are some comments on what I saw.

First general comments. The plants are actually doing quite well, maybe even a bit too well. There is plenty of new growth which is what you want but because they are so “happy” they are growing very quickly and thus you are getting big spaces between leaves and buds. This results in an “open” appearance.

Persimmon tree with open appearance
Many of your plants, now that they are getting lots of nutrients, water and in a great growing condition are now growing as fast as they can. This will result in larger plants that will start to flower or fruit further and further from the ground as they get closer to their mature size. Plants do this naturally because in nature they are always competing for sunlight and other resources that keep them alive.

How do slow them down? We focus on two things: reduce those “goodies” they are getting that encourage a lot of growth (water, fertilizer) and (this next part is harder to realize a bit) get the plant to reduce its own growth in each of its growing branches by increasing the total number of branches it has to support. This then causes the “goodies” that encourages growth to be divided up among many more growing points and slows it down. It’s like having an income of $50,000 a year and having to support three children or 20 children; your resources are divided up many more times  so each “child” gets less.

Generally speaking, reduce “goodies” by reducing your watering frequency (how many times you water per week if possible) and cut your fertilizer application in half (but not to the point where it is starving or gets leaf scorch) and (increase your children) prune. The type of pruning you will mostly do this winter will be what I call “heading cuts” rather “thinning cuts”. Heading cuts increase the total number of shoots in a tree while thinning cuts typically do not. If you want to see the difference, please visit my Youtube video on this subject

Now your individual trees, you must decide what you want for the ultimate height on these trees. If you want them to be large (such as flowering trees for beauty, shade or screening) then let them go and don’t do much pruning. If you want trees to be smaller and more compact (fruiting and harvest for instance) then you will cut them back pretty hard and take away from them their luxurious growth. You will prune these trees twice each year; once in the winter and again (taking away new fast luxurious growth) in April (summer pruning).
Magnolia with open canopy.

Crepe myrtle. I would assume you want a larger tree, perhaps with multiple trunks (3 to 5) coming from the ground. Don’t reduce the height. Let it go. Pruning will focus on removing dead, twiggy growth (it has lots of these due to flowering) and use thinning cuts to eliminate branches growing too close together, one branch growing on top of another, branches crossing each other, etc.).You can reduce the height by making thinning cuts and removing the tallest limbs and branches back to a “crotch”. I would not do much of this until it gets closer to the height you want it to get. You will fertilize in January with an all-purpose soil applied fertilizer such as 16-16-16 or even a rose fertilizer. You will see benefits from adding iron chelate to the soil in January and foliar applied fertilizers such as Miracle Gro about two or three weeks after the leaves emerge in the spring.

Magnolia. This is another tree you could elect to let it grow. Having a multiple trunked tree will help to keep it smaller. You realize that this tree is not a terribly good choice for our climate so you will spend more effort and money on this tree than many others. It will need the mulch which you are doing. This will give it some soil improvement near the soil surface as it decomposes. It will require a fertilizer application in January to push new, healthy growth. It will also benefit from an iron chelate. It will not most likely need a foliar fertilizer but it will not hurt it if you chose to apply it in February or March. Your choice but it might do better if it is kept smaller than the mature height it will try to reach. Perhaps if you can keep it in the 25 to 30 ft. range it will be easier to keep healthy. Perhaps saucer or star magnolia might work better in the future. Not as pretty but still pretty. There is a southern magnolia called Little Gem that is smaller.

Persimmon. Cut this tree back hard if you want your fruit closer to the ground. Your tree is too lanky. Cut back into older wood about half way in where it is too long in late January or early February. Don’t be afraid to do this. It will handle the hard cuts. Fruit is produced on current season wood so it will flower and fruit from new growth.

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