Bottle Trees and Leaf Drop

Q. I'm growing bottle trees together with mock orange and roses and these trees drop their leaves in the middle of summer. What can I do to prevent this?

Leaves on the ground beneath African sumac. One of the problems of African sumac is all the leaf litter it can produce in the middle of summer.Bottle trees can do the same thing.

A. I am starting to think differently about bottle trees. I am beginning to suspect that, like African sumac, some trees drop their leaves when it gets hot and others don't. Both of these trees originate from south of the equator in similar climates, one in South Africa and the other in Australia. Regardless, the best you can do is to prevent the soil from getting too dry and water trees 24 inches deep when you water.

Bottle tree limbs can die back with sunburn. Bottle tree is not a true desert plant but it has thin bark that can't handle a lot of direct intense sunlight.

Both of these trees are not "desert trees" but they are used commonly in desert landscapes. Both of them will handle soils that don't have a lot of organics in them so rock mulch is usually not a problem. This is not going to be true of roses or mock orange.

Japanese mock orange doesn't handle desert soils very well and will yellow if the soil is not improved at the time of planting, the soil is covered in rock for several years or if it's watered too often and the soils begin to drown. They don't come from the deserts of Japan.

Leaf drop or leaf litter is a big problem in African sumac and I get a lot of questions about it. It can also be a problem in bottle tree. But it's best to make sure the soil moisture does not drop too low or both of these trees will drop their leaves.

Roses should never be planted surrounded by rock or this will result in about four or five years. They are not true desert plants, just like Japanese mock orange or bottle tree or African sumac

Both roses and our mock orange (Pittosporum tobira) do not handle desert soils very well but they will tolerate a desert climate, high temperatures, low humidity.When I first moved to the desert in 1984, this plant had me confused with true mock orange which is actually Philadelphus coronarius.

So we should differentiate between the true mock orange and this one which I prefer to call Japanese mock orange. Japanese mock orange comes from the same area of the world that gives us Japanese blueberry.If you have been following me and some of the problems with Japanese blueberry in a desert climate, then you will know you don't want to put these plants with the name "Japanese" in front of it in desert soils in a desert climate or you're looking for trouble.

This is what happens to Wheeler's dwarf Japanese mockorange one you put it in full sun, cover the soil with rock and water it every day or too often.

Like I tell people, there is no such thing as the "deserts of Japan". Okay, Japan has one but there are no plants there! So don't treat it like a true desert plant. Both of them are not.Don't get me started on Carolina cherry laurel and the deserts of North and South Carolina! (Except for Jockeys Ridge!)

The default on your situation are the roses and Japanese mock orange. They like soils that are improved over raw desert soil which the bottled tree will be happy about. So cover the soil beneath these plants with at least 4 inches of wood chip mulch. Beneath the mulch spread a couple of bags of high quality compost like Viragrow's Soil Pro.

There goes soil Pro compost is a compost rich in nutrients. No fertilizer will be necessary for one to two years after applying it.

Use a soil moisture sensor to help you judge when to irrigate again until you get it under your belt, and use a long piece of skinny rebar to make sure you gave these plants enough minutes.

A skinny piece of rebar like this three sixteenths inch diameter is good enough to use for determining the depth of watering. Water small shrubs 12 inches deep. Medium-size trees 18 inches deep. Medium to large sized trees 24 inches deep. Really big trees 36 inches deep

 The roses and Japanese mock orange can handle irrigation 12 inches deep while the bottle tree likes watered down to about 24 inches deep. If these plants are on the same irrigation valve, use drip emitters that are high-volume under the bottle tree and use moderate volume drip emitters with the roses and Japanese mock orange.