The olive tree grows slowly and keeps its leathery foliage all year. Olive trees will bear fruit when they reach about 5 years old under the proper care and conditions. Some varieties of olive tree remain fruitless; growers keep these as purely ornamental specimens. If you live in an area with conditions unsuitable for growing olive trees, you can grow yours indoors. These indoor, container-grown trees will need special care so they receive enough sun and proper moisture to remain healthy.
Location and Planting Zones
Olive trees need warm temperatures during their growing season and cannot survive temperatures lower than 10 degrees. If you live in an area colder than zone 8 on the plant hardiness zone map, you may place your tree outdoors in summer, but will need to bring it inside for the winter. Your olive tree will need a sunny, south-facing window where it will receive at least six hours of direct sun every day. To prevent damage to the tree's foliage, place it away from heat vents. Keep it at least 4 to 5 inches from the window; the glass can intensify the sunlight and burn the leaves.
Olive trees do not thrive in soggy conditions. Wait until the potting mix feels dry an inch down before watering. Water your olive tree until the soil is moist but not soggy. The tree will require less water during the winter months when its growth slows down, but you'll still need to check it regularly to prevent the mix from drying out all the way down.
During the slow growth phase in fall and winter, fertilize your olive tree monthly with a balanced fertilizer for houseplants, such as 20-20-20. During active growth in spring and summer, you can fertilize every two weeks or give your tree a timed-release fertilizer.
Olive trees are usually self-fertile, meaning they do not need both a male and female tree in order to produce fruit, but they tend to produce bigger harvests if they can cross-pollinate with another tree. If you purchase two olive trees to cross-pollinate, be sure to choose two of the same variety, or two varieties that bloom at the same time.
Each branch on your olive tree should remain at least 6 inches long; otherwise, you can prune the tree to the shape you like. Thin your young tree to three or four main branches, and clip the branch tips in early spring to encourage a bushy shape. Your pruning cuts should be about an inch above the point where a leaf pair attaches to the stem.
If you choose to move your tree outside during the summer, wait until all chance of frost has passed in your area. Your olive tree will need to get used to the outdoor conditions gradually; you can accomplish this by placing it outside for short periods and extending these periods over the course of a week. In the autumn before the first frost in your area, reverse the process to acclimate your tree to indoor conditions. Olive trees benefit from a dormant stage in the winter and will do best in a cool room with a south- or west-facing window.
Soft-bodied scale insects will sometimes attack olive trees. These insects have small, yellow-brown bodies and attach themselves to the plant's stem to suck its sap. You can treat a scale infestation with insecticidal soap or other insecticidal products labeled for indoor plant use. For small infestations, you can also dab individual insects with a cotton swab dipped in rubbing alcohol; this method may not be effective for large infestations or to entirely eradicate the pests.