Q. I have bottle trees planted next to the house and for some reason the one in the middle is losing leaves on the bottom branches. The trees are getting watered two times each week for 40 minutes. I cleared out the rock mulch and replaced it with cedar mulch around the base of the tree. I lost a bottle tree last year so I'm trying to figure out why.
A. Bottle trees represent about 15 or 20 different types. All of them have a swollen trunk which, some people speculate, they use for storing some water during dry periods. We typically use only one type of bottle tree in the valley.
The cedar mulch won't add any nutrients to the soil but it will slow evaporation of water from the soil surface. Bend side branches without leaves to see if they are dead. If they are still flexible and don't snap, they may come back when it cools.
Remove any branches that are growing toward the house. Planting those trees in that location was not the best idea.
I remember these trees being brought into the valley as early as the late 1980s during our first push on desert landscaping. They were brought in by landscape contractors and architects because they were being used primarily in Southern California.
The first problem I remember was irrigation. People did not know that these trees required watering less often. They were watering them much like any other landscape plant. These trees are very susceptible to over irrigating.
Although not a desert tree like the Acacia, it does handle arid climates and infrequent waterings. These waterings, when they do occur, should flood the entire root system about 2 to 3 times a month during the summer. The next irrigation should not occur until the soil is dry or you run the chance of getting root rot and the tree may suddenly die during the summer heat.
The next problem was how they were being used. The tree needs to be in full sun. They should not be planted against hot South or West facing wall. Very young, green trunks of this tree can get severe sunscald in these locations followed by limb and branch death.