Olive trees (Olea europea) are found in most tropical region in the world. Breeds originated in the Mediterranean, as well as parts of Asia and Africa and were introduced to the United States in the 1700s. Most breeds are hearty enough to withstand cold winters, as well as harsh soil and conditions. The trees are evergreen and live for as long as 500 years and have been reported to grow back even when chopped down. A mature olive tree can reach a height of 50 feet tall with branches stretching as far as 30 feet across. With some winter precautions, the health and steady growth of the tree can be ensured for years.
Native to the Mediterranean, Olive trees grow and produce best in warm weather. Proper growth and olive production requires a long, hot growing season. In areas where the weather reaches below -2.22 degrees C, the tree grows as an ornamental. Trees in these cooler regions still grow tall and have the well-known look of a standard olive tree, but will not produce fruit. Late spring frosts and extremely cold winters hinder such growth. Early development fruit will be damaged if temperatures dip below -1.11 degrees C, while more mature olives will withstand these lower temperatures. Cold-weather ornamentals should be protected from cold weather using horticultural fleece whenever necessary. Cover the crown and trunk of the tree to avoid frost or other damage in chilly weather.
Pruning is important. Even though the trees are evergreen, they undergo a winter resting period where little or no growth takes place. Do not prune during the colder months, as damage may be done to the branches, causing a decline in olive production. New trees should not be planted until spring. This resting period prohibits healthy root development and results in the death of the tree. The trees are hearty and will often withstand substantial neglect, although care should be taken to shelter unripe fruit from heavy winds.
For gardeners in United States Department of Agriculture Plant Hardiness Zones colder than Zone 8, where weather dips below -12.2 degrees C, planting and growing an olive tree indoors is fairly common. The chosen space must have at least six hours of direct sun per day making south-facing windows ideal. When dealing with an indoor atmosphere, reduce the plants exposure to heat vents, radiators and other heat sources. Avoid moving it too close to a window. The tree requires less water throughout fall and winter, but do not allow soil to become completely dry. Use a soil mix providing fast drainage and a container with a hole at the bottom. Standing water opens the trees shallow roots up to fungal infection and other damage.