The climate of Southern California is classified as a semi-arid Mediterranean climate. These conditions are perfect for growing olive trees, a plant native to the Mediterranean. Here in San Diego, olive trees are abundant. With their soft grey leaves and gnarled trunks, they add beauty and interest to the landscape. Yet, when the trees produce olives, the fruit drops and creates unsightly black, oily olive stains that are a nuisance for property owners and landscaping companies to remove. Spraying olive trees for fruit prevents olives from fully forming, and thus prevents messy olive stains. It can also be beneficial to the tree, since large amounts of fruit won’t weigh down the branches.
When to Spray Olive Trees for Fruit
The best time to spray will vary from tree to tree, but normally it should be done in mid-spring. The easiest way to know when the time is right is to observe the tree’s flowers. Once the flowers have bloomed, you’ll want to wait about 1 ½ to 2 weeks to spray the tree. At this point, the flowers should be fully open but the olive buds have not started to form. The period of time when blossoms are opened is usually quite short, about 1 to 3 days, so stay vigilant!
What to Spray to Prevent Olive Trees from Producing Olives
Using a growth regulator is the easiest way to prevent the tree from bearing fruit. For most growth regulators, the regulator is mixed with water and poured into a garden sprayer to be applied to as many flower buds as possible. Growth regulators cause the tree to release ethylene, a hormone that gets released when trees are stressed. When the tree releases this hormone, it puts the tree in self-defense mode. It will stop producing olives, even though it is not actually stressed or in danger; however, some research has shown that consecutive years of growth hormone applications may induce or compound existing stress symptoms. So, it is important to evaluate the overall health of the tree prior to any applications of growth regulators. Contact your landscape professional to get more information on when and how to apply growth regulators.
Where to Spray Olive Trees to Prevent Olives
To prevent olive production, each tree blossom needs to be sprayed inside and out with growth regulator. If one blossom is missed or not thoroughly sprayed, it may turn into an olive. Most fruit reduction treatments are meant to do just that, reduce the size and/or number of fruit. Complete fruit prevention is nearly impossible to achieve.
Tips for Spraying Olive Trees
– Allow the growth regulator to completely dry on the tree. This could take around 4-5 hours. Do not spray the tree when rain is expected or a sprinkler system is scheduled to run. Calm winds are essential to ensure proper flower bud coverage and reduce the chance of the growth regulator drifting to non-targeted plants.
– Make sure the tree receives ample amounts of water during this process. Remember, the tree is going into a man-made stressed state, so keeping the tree hydrated is very important. Following the application of the growth regulator, provide the tree with a continuous supply of water for up to two hours.
– If preventing olive stains is more important than enjoying the olive tree flowers, the tree can be sprayed prior to bud break. Note that if the tree is sprayed too early, there will be limited fruit reduction. Flower buds should be present in some form to get maximum effectiveness.
– For new plantings where fruit could be an issue, fruitless olive varieties are widely available.
Other Trees that can be Sprayed to Prevent Fruit
– Crabapple tree
– Plum Tree
– Mulberry Tree
– Liquid Amber
– Flowering Pear
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