Fruitless olive trees are very attractive shade trees that can be either single or multi-branched, with eye-catching, twisting, and contorted trunks and an airy mass of gray-green leaves with silvery undersides. They are very similar in appearance to fruiting olive trees, but there are few to no messy fruits produced to litter the yard.
The term fruitless can be a bit of an overstatement and some homeowners are unpleasantly surprised when they see a handful of tiny olives forming on the branches. Fruitless olive trees will bloom in spring with clusters of yellowish-white, tubular flowers. The flowers are sterile, so few if any fruits are produced, but some small, probably non-viable, olives may develop from time to time. However, they are minimal and you will not notice them when they have fallen from the tree.
Fruitless olives offer a big advantage if you live in an area of the Southwest where fruiting olive trees are banned, either because of the widespread mess created by the falling fruits or the allergy-triggering pollen. The fallen olive fruits will stain driveways, paved areas, and decks; clog drains; and attract unwanted animals as they decompose. Fruitless olives spare you from all of these problems.
USDA Hardiness Zones
Fruitless olives are hardy in USDA zones 8–11 (Sunset Climate Zones 8, 9, and 11–24). The trees can handle desert heat and cold and can tolerate some short-term frost. They are generally hardy down to 15–20 degrees Fahrenheit.
Full sun is needed for healthy growth.
Mature Tree Size
Non-fruiting olive trees grow to an average of 25–30 feet x 25–30 feet. This makes them a medium-size tree in the landscape. It is the possible 30 feet in width that homeowners should carefully consider. If you plant near your house or patio, branches will eventually encroach. Do not be fooled by fruitless olive trees' slow to moderate growth speed. They may take 10 or more years to reach full size, but they will get there.
Planting a Fruitless Olive Tree
Choose your site wisely, because fruitless olive trees can live for several hundreds of years. To grow healthy and disease-free, a fruitless olive tree needs a spot that gets at least eight hours of sun a day. It also requires well-draining soil, because it can be susceptible to root rot if the soil remains damp for prolonged periods.
Although fruitless olive trees are very drought tolerant, you should give them some supplemental water while they are first becoming established, especially during extreme heat and dry periods.
Caring for Fruitless Olive Trees
Once your fruitless olive is established, it requires very little care. They are extremely drought tolerant and prone to a few problems or pests.
The trees can produce suckers and may need to be pruned annually to keep their shape.
While young, an annual application of high-nitrogen fertilizer in spring will encourage new healthy growth.
If you would like to try and prevent your fruitless olive tree from producing any fruit at all, you can do some light pruning of the newer growth branches. These are the branches with flowers that will turn into olives. Don't go overboard with pruning and destroy the shape of the tree.
You could also apply a fruit-inhibiting spray containing ethylene. Spraying needs to be timed to when the flowers are forming and is costly to apply every year, especially as the tree grows larger. Most people do not find this a very practical option.
Using Non-fruiting Olive Trees in Landscape
With their contorted shape, fruitless olive trees make beautiful specimen plants in the lawn. They are also lovely lining a driveway (make sure they are fruitless) or some other long pathway.
The dwarf varieties can be pruned into topiary or even bonsai forms. Planted in a line and sheared, fruitless olives make a very attractive hedge.
Pests and Problems of Nonfruiting Olive Trees
- Borers: The branch and twig borer, a type of beetle, will bore holes into the tree to lay its eggs. The newly hatched borers will burrow even further into the tree and can eventually kill the twig or branch they are in. The American plum borer, which is a type of moth, can cause similar damage. Prune out any twigs or branches with visible holes to prevent further damage.
- Scale: These tiny, hard-shelled insects adhere to various parts of the tree and feed on it with their piercing mouths. This can weaken the tree and cause die-black. You may be able to treat the problem by smothering the scale with horticultural oil, but scale insects are most easily controlled when they are in their "crawler stage," shortly after they hatch and before they develop their hard outer coating. Check with your local cooperative extension for when that happens in your area.
Several fungal diseases can affect fruitless olive trees. Good air circulation and plenty of sunshine will help prevent these diseases. If you suspect your tree is suffering from a fungal disease, it is best to take a sample to your local cooperative extension or a good nursery and ask them which disease it is and what is the best way of treating it.
Browning leaves and loss of leaves is usually caused by either insufficient water or waterlogged soil. Be sure to provide good drainage and regular water. This is even more essential with container-grown trees.
Suggested Fruitless Olive Trees for the Home Landscape
- 'Majestic Beauty': Most reliably non-fruiting.
- 'Swan Hill': Rarely produces fruits and is also pollen-free.
- 'Wilsonii': Beautiful, hardy trees, but may produce enough fruits to be noticeable.
- 'Little Ollie' and 'Skylark Dwarf': Compact varieties that are good for patios and containers.