Newly Planted Tree Shows Leaf Death and Die Back

Q. About three weeks ago I bought and planted a 12 X12 crepe myrtle tree. I used grow mulch and compost watering it once a day since then. Now the tree branches seem to be losing its leaves. Could I be over watering the tree?  What could you suggest I do to make sure the tree grows healthy? 

Small crepe Myrtle tree, Not the readers

A. Why would you tree have yellowing or scorching leaves that are falling off?

Plant got too dry at the nursery before it was delivered

• Plant was delivered in an open truck and the leaves were battered by the wind
• Plant got too dry before it was put in the ground
• Plant was put into a dry hole and the roots became desiccated or dried out for water was applied. This can happen in minutes.
• Plant root ball fell apart when it was put into the planting holeSalt levels were too high in the soil or the planting mix or both and not leached with enough water at the time of planting
• Watering daily after it was planted
• Not watering often enough or with enough water after it was planted

At the time of planting, the soil in the hole, and all of its contents, should be wet. The soil should be checked to make sure that it drains several inches of water in no more than a few hours. If the soil drains adequately, the hole needs to be dug no deeper than the box.

In our desert soils with extremely low organic matter, it is best to use the soil that was dug from the hole and amend it with a planter mix amendment in a ratio of about 1:1 by volume. To help prevent transplant shock the tree should be planted as soon as humanly possible after delivery.

To help prevent transplant shock further the tree should be planted into a hole that was wet and allowed to drain. The wooden box must be removed from around the root ball at the time of planting.

This is done by leaning the tree over on its side, removing the bottom of the wooden box, pushing it back to an upright position, lowering it carefully into the hole, removing the rest of the box, and adding the backfill.

Box tree planted in the landscape. The bottom of the box is removed before placing it gently into the hole. Sides of the container is removed, the root ball is watered and the amended backfill is used to fill the hole, watering the hole as the backfill is added.

As the amended backfill soil is added to the hole, water from a hose should be running into the planting hole keeping everything inside wet. After planting, a donut shaped basin 4 inches high should be constructed around the perimeter of the planting hole.

Fill this basin twice every time you irrigate for the first two weeks after planting. Fill the basin approximately every three days. I would not rely on a drip irrigation system for delivering the water needed by the tree immediately after planting.

After 2 to 3 weeks you can begin to wean the tree from water applied by the hose and begin to integrate your drip irrigation into your watering cycle. You would do this by putting the drip irrigation on a normal schedule for landscape trees in our climate and continue to fill the basin once a week to supplement the drip irrigation and removal of any high levels of salts from the soils.

Some landscape companies leave the drip irrigation to come on daily to try and accomplish the same thing but that can be dangerous because they don't tell the homeowner to reset the clock or they forget to reset it themselves.

Three things you must regulate when you irrigate: 

how much you apply at each irrigation, 

how often the irrigation is applied and 

the time of day water is applied. 

Make sure your drip irrigation system is applying enough water every time it comes on.

It is difficult to tell you the number of minutes this equals without knowing the number of drip emitters and their gallons per hour rates of water application. The other thing needed is the size of the tree; its height and the size of its container.

How often your irrigation system delivers water depends on the time of year and the type of plant. Trees and large shrubs are watered less often than anything else in the landscape. This time of year we are beginning to cool so applying water twice a week, as long is it is enough water, will be often enough.

Time of day the application is made is the least critical feature. However, ideally the irrigation should come on just prior to the heat of the day.