Q: I have an olive tree, which would be at least 25 years old. This year it has given me one olive. The blossom this year was the heaviest ever, the fruit form then disappear. I have had fruit from it when it was younger. I have never fed it.
Question from J. Belcher, via email
A: If the tree does form fruit then the most likely culprit is birds eating the fruit. A wide range of introduced birds are known to eat olives including blackbirds, song thrushes, starlings, doves and mynahs, and it’s likely many native birds feed on them, too. They often swallow the berry whole and fly off to digest the fruit and poop out the seeds elsewhere. There are reports overseas, including Australia, of wild olive trees appearing as a result of birds spreading the seeds. You could take some measures to deter birds by covering the tree with bird netting or by hanging shiny reflective things such as foil plates or old CDs in the trees which seem to scare some birds away, though often only for short time until they get used to them.
Planting olives is in vogue at the moment but there are two problems we may have face in the future as a result: dealing with olive tree weeds and the allergy problems associated with olive pollen. They are related to privet (in the family Oleaceae) and olive pollen allergy symptoms are similar to those of privet.
Answer by Andrew Maloy (The Plant Doctor)