Master Gardener Laura Simpson answers your questions and offers gardening tips.
Q. What is sudden branch drop syndrome? Is there any way to prevent it?
Sudden branch drop syndrome (also known as summer branch drop or summer branch limb failure) occurs when a limb from a presumably healthy tree just breaks off and falls without any warning.
Sometimes you can predict that a branch is going to break. If there are signs of insect infestation, cracking, or obvious structural imbalance, there’s a chance that something bad is going to happen. Sudden branch drop, on the other hand, occurs without warning.
There’s been plenty of research done on this phenomenon, but no clear cause has been found yet. Sudden branch drop usually occurs during hot, dry conditions, so researchers suspect water stress as a major factor.
Although no definitive cause has been determined, there are some factors that seem to contribute to the likelihood of sudden branch drop. Structural factors, such as excessively horizontal branch angle and bad pruning, appear to be major contributors. Excessive moisture within the wood, coupled with hot, dry weather conditions, seem to also contribute to limb drop.
Proper pruning and tree shaping can minimize the risks associated with sudden limb drop. Species especially prone to limb drop include oak, elm, sycamore, eucalyptus, and beech. For some reason, the presence of an expensive car directly under a large limb seems to increase the chances of a catastrophic branch failure.
Q. I have a plum tree that was planted over 10 years ago on my property. I have been seeing sprouts coming up all around the tree, sometimes quite far from the original tree. Are these offshoots from the tree? What is causing this?
Some tree species naturally send out suckers as part of their natural growth habit. Sometimes trees will do this if there’s any kind of root damage, such as that caused by an injury incurred during transplanting or gopher damage.
In the case of your plum tree, presumably, it’s a grafted tree. Most fruit trees are grafted onto a dwarfing rootstock for several reasons. The rootstock often has resistance to soil-borne diseases or is tolerant of certain adverse soil conditions, allowing a tree to grow and thrive where it might not otherwise. The rootstock also prevents the tree from growing too tall, making fruit harvest much safer and easier. Some rootstocks tend to send out multitudes of suckers, particularly the rootstocks used in grafting plum trees. If these suckers are allowed to grow, they may produce fruit of their own, but it won’t resemble the fruit from the grafted tree. I recommend clipping (or sawing) off the suckers at soil level. In our experience, if you try to dig them out, you’ll damage the roots which will cause the tree to petulantly send forth even more suckers.
Los Angeles County
mglosangeleshelpline@ucdavis.edu; 626-586-1988; http://celosangeles.ucanr.edu/UC_Master_Gardener_Program/
Orange County
ucceocmghotline@ucanr.edu; 949-809-9760; http://mgorange.ucanr.edu/
Riverside County
anrmgriverside@ucanr.edu; 951-683-6491 ext. 231; https://ucanr.edu/sites/RiversideMG/
San Bernardino County
mgsanbern@ucanr.edu; 909-387-2182; http://mgsb.ucanr.edu
