by onward » Mon 09 Jan, 2017 7:50 pm
The propensity to drop limbs during calm periods is called sudden branch drop (and sometimes summer branch drop), it is generally associated with eucalypts in Australia, but is common in a wide range of species overseas (I would guess based on the commonality of the species, and gums are very common in Aus!!!). There are quite a few theories as to the reason, but no real scientific data. Calm days, after a dry spell and often the most horizontal branch is the typical scenario. Particular trees seem to do it more frequently. Look up, if the tree has dropped previous larger branches, and has longer horizontal branches don't put a tent under it! Wind typically causes failures in branches with identifiable defects (e.g., decay)