Q. My Australian bottle tree and African sumac are shedding leaves like a maple tree during fall. However, they are also putting on new growth. I specifically chose these trees because they remain green all year long. The bottle tree is about 20 ft. tall, on the north side of the house and gets about 20 gallons of water every day during the summer. The sumac is on the west side and is about 12 ft. tall and gets about the same amount of water. I’m about ready to cut them down due this leaf shedding. Were they stressed during the heat wave or what?
A. These two trees have very different watering requirements. The bottle tree is a true desert adapted tree while the African sumac is not. Their watering needs are very different for this reason.
The bottle tree should never get daily watering. Even though the watering needs of the African sumac are more frequent, it should not get watered daily either. It is possible that these trees are dropping leaves excessively because their roots cannot “breathe” due to excessive moisture in the soil.
|Bottle tree in desert landscape|
At the most, the sumac should get watered deeply twice a week right about now. The bottle tree less often than that but when it does get water it should be deeply as well.
Evergreen trees do drop their leaves. No plant is without leaf drop. Some keep their leaves longer than others.
Normal leaf drop time for evergreen plants is during or shortly after new growth. As they put new growth and new leaves on new branches they drop older leaves from older wood. This is normal. However, excessive leaf drop is not. This can indicate stress ranging from drought to overwatering.
Please get on a deep and infrequent watering schedule rather than a daily one. This time of year the only things watered daily are fescue lawns, annual flower beds and vegetables. The larger the plant, generally speaking, the deeper the root system, the less frequent the watering but the amount of water applied each time is higher.
Frequent, shallow irrigations force roots to grow shallower and decrease their tolerance to droughty conditions. Both of these trees can develop root rot from frequent watering and death. Excessive leaf drop can be a sign that this is happening.
|Bottle tree in lawn|
I would begin to back off to watering every other day for right now but increase the amount you give them each time you water. Both can handle the heat but not daily watering, particularly the bottle tree.
Make sure the applied water is distributed evenly under the canopy either by having several drip emitters under them or watering them in a basin and flooding the basin. The water should not be applied in one location under the canopy. Back off on the daily watering. I hope they are not in stages where you can keep them from getting worse.