Olive trees grown indoors live eight to nine years, a much shorter lifespan than olive trees in the landscape, which are known for their longevity. The best you can do for the tree is to move it outdoors during the summer months because even the best indoor conditions can’t match preferred conditions outdoors. Aside from those caveats, slow-growing olive trees are easy to care for indoors. Although olive trees can be pruned to keep them small, consider choosing a compact or dwarf variety such as ‘Little Ollie’ (Olea europaea ‘Montra’) to grow indoors.
Indoor Olive Tree Care
Growing an olive tree indoors is not difficult but it is important that a few key requirements are met.
Light
Olive trees require at least six hours of direct sunlight per day. A large south-facing window is the only indoor location that can provide the necessary sun exposure. Make sure the leaves do not touch the window glass, which can cause them to become scorched. To ensure equal light exposure on all sides, turn the pot 90 degrees every week. If your home does not offer sufficient natural light, you can also set up a grow light. Leave it on for at least six hours every day, increasing this to eight hours if you aren’t able to move the tree outdoors in summer. Full-spectrum light is best, as it comes the closest to sunlight at midday, in a combination of red and blue lights for overall healthy plant growth. LED lights are the most energy-efficient and long-lasting solution.
Temperature and Humidity
In their native Mediterranean climate, summers are hot and dry with low humidity and winters are cool and moist. For an olive tree grown indoors, a room temperature between 65 and 80 degrees Fahrenheit is best. Because it can withstand dry air, keeping it in a heated room of up to 40% relative humidity is fine. However, the plant should be kept away from heat vents and radiators to prevent drying out.
Watering
The soil of a potted olive tree should never fully dry out, but be careful not to overwater. When the soil is dry to a depth of 1 inch (stick your index finger in the soil to check), water slowly and deeply until the soil is soaked and water trickles out of the drainage holes. In the winter, when the tree is dormant, it will require less water but a dry top layer of soil indicates the tree should be watered.
Fertilizer
Olive trees in the landscape don’t need much fertilizer. Potted olives have slightly higher needs as fertilizer gets washed out of the potting soil, but they are still light feeders. Starting in the early spring and throughout the summer, feed the tree once a month with a balanced slow-release houseplant fertilizer. As for the amount, follow the label instructions, as the nutrient content of fertilizers varies. Stop fertilizing the tree in the fall and don’t fertilize it during its dormancy period in the winter.
Pruning and Maintenance
Over time, an olive tree can get spindly. Pruning in the spring when new growth starts encourages a bushy growth habit. Using sharp hand pruners, cut ¼ inch above a leaf node (where the leaf is attached to the stem) at a 45-degree angle. New branches will develop from the node. Remove branches growing from the base and thin out branches in the center of the tree. This allows plenty of sunlight exposure and good air circulation for the entire plant.
Container and Size
A 16 to 20 inch deep container works for most standard-size olive trees purchased from a nursery. Plastic containers are ok, but keep in mind plastic heats up more than breathable natural materials such as ceramic, terra cotta, or wood. If you move the tree outside in summer, setting the plastic pot inside a larger pot will help insulate the roots and keep them from overheating. Excellent drainage is crucial for olive trees so choose a pot with large drainage holes. Make sure the holes don’t become obstructed. Elevating the container on plant feet or blocks or placing it on a ridged saucer will help.
Potting Soil and Drainage
Commercial well-draining potting mix or cactus potting mix works well for olive trees. Or you can mix in perlite, bark chips, or small gravel. Do not add compost or mulch because organically enriched soil retains too much moisture for these trees that won’t tolerate soggy, wet soil. Some growers recommend adding gravel to the bottom of the pot. Whether this improves drainage is a subject of debate however the extra weight can help stabilize a pot made of light material like plastic.
Potting and Repotting Olive Trees
It’s time to repot your tree when the roots reach the sides of the container or grow out of the drainage holes. Olive trees grow slowly so your plant might not require repotting for two to three years. The new container should be 25 percent larger than the root ball, or at least 2 inches larger than the root ball all around. Make sure that in the new container, the stem is above the soil level and not buried, as this could lead to root rot.
Moving Olive Trees Outdoors for the Summer
If you are able, you should move your tree outdoors during the warm months. Wait until nighttime temperatures are consistently above 40 degrees Fahrenheit, to avoid cold or frost damage. The tree should be adjusted gradually to outdoor conditions. Start by placing it in a spot where it is sheltered from wind and full sun for several days. After that, you can put it in its permanent summer location.
Overwintering
When nighttime temperatures drop below 40 degree Fahrenheit in the fall the tree should be brought indoors. Gradually acclimate it to the lower light conditions by placing it in a partially shaded location for about one week, then bring it back inside. Olive trees attract ants, scale insects, and spittlebugs. To avoid bringing them inside, give the tree a thorough spray with a hose (cover the soil with a piece of plastic while hosing it off so you don’t drench the soil).
