Olea
( oh - LEE - uh )
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At-A-Glance InformationThe genus Olea is native to temperate and tropical regions of the Middle East, southern Europe, Africa, southern Asia, and Australasia. The group includes evergreen trees and shrubs that produce small drupe fruits. The most commercially important and well-known species is Olea europea, what most people know as Olive Tree. These trees can live for centuries, and are fantastic for smaller gardens, growing in groves, or for use as shade trees in the landscape.
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Olea Species and Varietals
The genus Olea is the type member of the plant family Oleaceae and includes 12 species. Species previously included in the genus have been moved to genera Chionanthus and Osmanthus. To find your zone, click here: Zone Map.
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Olea capensis (Black Ironwood, Ironwood Olive, East African Olive, Elgon Olive) These African trees are widespread in Somalia, Ethiopia, Sudan, Cameroon, Sierra Leone, Madagascar, and the Comoros, where they grow in scrub and forest areas. |
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Olea chimanimani These shrubs and small trees reach between 6.5 and 10 feet tall when mature, and are only found in the Chimanimani Mountains that divide Zimbabwe and Mozambique. They prefer scrub and cliffside environements. |
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Olea europea (Olive, Dwarf Olive, Little Olive) This species is widely cultivated for its edible fruits, and is the type species in the genus Olea. These plants grow as either trees or shrubs, in the latter case being known as Dwarf Olive, or Olea europea 'Montra'. Flowers are small, white and 'feathery', and fruits that follow are harvested when purple or green. Trunks are typically gnarled and twisted, especially so in old age, and trees top out around 25 to 50 feet tall. |
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Olea paniculata (Native Olive, Australian Olive, Pigeonberry Ash, Maulwood, Clove Berry) These trees are native to Pakistan through China and tropical Asia, as well as Australia and the Pacific Islands. It grows as a bushy tree to 98 feet tall when mature. Fruits are blue-black and ripen from May through September. Known as a pioneer species on sunny protected areas, these trees prefer very well-draining soil and attract both butterflies and birds to the garden. |
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Olea welwitschii (Elgon Teak) This species of Olea is native to subsaharan Africa, where it grows in lowland tropical rainforests and evergreen montane forests. These evergreen trees reach up to 115 feet tall and are used in their native range as a timber tree species. The species is named for botanist Friedrich Welwitsch. |
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Olea woodiana (Forest Olive, Black Ironwood, Bosolienhout) This African Olive species grows in low-elevation forests in Kenya, Tanzania, Eswatini, and South Africa. These medium-sized to tall trees produce small white fragrant flowers followed by fruits in late summer. Olive fruits are commonly consumed by local birds. |
Caring for and pruning Olea Trees
Plant Olive trees in a spot in the garden that receives full sun. Ensure that trees are getting between 6 and 8 hours of direct sun each day. They will flower and fruit better with this exposure. Trees prefer well-draining, sandy or loamy soil with a pH of between 5.5 and 8.0. Avoid planting Olive trees in clay or waterlogged soils. If local soils are too heavy, consider amending the planting site with plenty of organic material and/or sand before installing trees. Apply a thick layer of mulch around the base of trees to suppress weed growth, increase soil moisture retention, and help to regulate soil temperatures. Water new plantings regularly as they develop strong root systems. During dry spells, make sure to provide extra deep waterings. Established trees are somewhat drought-tolerant, but do perform best with consistent moisture. Water deeply every two to four weeks, especially during long dry periods of the year, and allow soil to dry out somewhat between waterings to discourage fungal root rot issues.
These trees do not require heavy feedings and typically do well with a simple application of organic compost to their root zone yearly in springtime. If trees seem to be struggling or foliage is somewhat discolored, trees may benefit from an extra feeding with a balanced, slow-release fertilizer (such as a 10-10-10). Avoid over-fertilizing trees, as this can negatively affect their growth and development over time. These trees also don't require heavy prunings, and have a natural pyramidal shape. Prunings should focus on maintaining this form instead of changing it. In late winter or early springtime, remove dead, broken, or diseased branches and lightly shape the canopy by removing crossing or poorly placed branches. Don't prune off too much foliage at any one time, as this can damage the tree and open it up to attacks from pests and disease. Make sure that dense growth is thinned in order to improve light penetration as well as flower and subsequent fruit production.
Olive trees can be grown in-ground or in containers. If choosing to grow an Olive tree in a container, ensure that soil is well-draining (and amended with plenty of sand or perlite), and that the container has adequate drainage holes in the bottom. The upside of growing Olive trees in containers is that they can be moved indoors or to a more protected spot during the cooler fall and winter months. These trees will need to be repotted every two to three years in order to keep up the health of the tree and ensure that they are not becoming root-bound. When repotting, choose a pot that is between 2 and 4 inches wider in diameter than the previous one, and make sure to add more well-draining soil.
Harvesting Olives
Depending on the species and variety grown, Olive fruits ripen from late summer to early wintertime. They are typically harvested by hand, and can be picked off of their attachments to trees or picked off the ground after branches are shaken. Ripe fruits will be either black or green, depending on how they will be used. Green and black olives come from the same trees, but are just picked at different levels of ripeness. Green olives undergo a fermentation process that involves soaking in a lye solution before produces cure them in a salt brine. Black olives, on the other hand, skip the fermentation process and are cured right away. Fruits are not edible fresh, and once harvested, need to be processed quickly to avoid them oxidizing. Once they have been harvested, bring olives indoors and rise them under cold water to remove dirt, dust, and anything else they may have picked up while out in the landscape. If desired, remove the pits from the washed olives using a cherry pitter or other tool (like a broad-sided knife). Place olives in an airtight container in a brine or salt solution for three to six months' time. Olives can also be pressed to make olive oil, but it takes a large amount of olives to make oil. It typically takes between 75 to 125 pounds of olives to make a gallon of olive oil. Fully mature trees will produce between 20 and 80 pounds of olives each year, and older, larger trees can produce up to 400 pounds of olives per year.
These trees do not require heavy feedings and typically do well with a simple application of organic compost to their root zone yearly in springtime. If trees seem to be struggling or foliage is somewhat discolored, trees may benefit from an extra feeding with a balanced, slow-release fertilizer (such as a 10-10-10). Avoid over-fertilizing trees, as this can negatively affect their growth and development over time. These trees also don't require heavy prunings, and have a natural pyramidal shape. Prunings should focus on maintaining this form instead of changing it. In late winter or early springtime, remove dead, broken, or diseased branches and lightly shape the canopy by removing crossing or poorly placed branches. Don't prune off too much foliage at any one time, as this can damage the tree and open it up to attacks from pests and disease. Make sure that dense growth is thinned in order to improve light penetration as well as flower and subsequent fruit production.
Olive trees can be grown in-ground or in containers. If choosing to grow an Olive tree in a container, ensure that soil is well-draining (and amended with plenty of sand or perlite), and that the container has adequate drainage holes in the bottom. The upside of growing Olive trees in containers is that they can be moved indoors or to a more protected spot during the cooler fall and winter months. These trees will need to be repotted every two to three years in order to keep up the health of the tree and ensure that they are not becoming root-bound. When repotting, choose a pot that is between 2 and 4 inches wider in diameter than the previous one, and make sure to add more well-draining soil.
Harvesting Olives
Depending on the species and variety grown, Olive fruits ripen from late summer to early wintertime. They are typically harvested by hand, and can be picked off of their attachments to trees or picked off the ground after branches are shaken. Ripe fruits will be either black or green, depending on how they will be used. Green and black olives come from the same trees, but are just picked at different levels of ripeness. Green olives undergo a fermentation process that involves soaking in a lye solution before produces cure them in a salt brine. Black olives, on the other hand, skip the fermentation process and are cured right away. Fruits are not edible fresh, and once harvested, need to be processed quickly to avoid them oxidizing. Once they have been harvested, bring olives indoors and rise them under cold water to remove dirt, dust, and anything else they may have picked up while out in the landscape. If desired, remove the pits from the washed olives using a cherry pitter or other tool (like a broad-sided knife). Place olives in an airtight container in a brine or salt solution for three to six months' time. Olives can also be pressed to make olive oil, but it takes a large amount of olives to make oil. It typically takes between 75 to 125 pounds of olives to make a gallon of olive oil. Fully mature trees will produce between 20 and 80 pounds of olives each year, and older, larger trees can produce up to 400 pounds of olives per year.
Propagation
Olea, or Olive trees can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Olive tree, follow the instructions below:
Propagating Olea by Cutting
Propagating Olea by Seed
Propagating Olea by Cutting
- Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
- In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Scrape a 1/2 inch long and 1/4 inch wide section of bark off of the bottom of the cutting. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot so that about half of the height of the cutting is under the soil surface. Fill in soil around the cutting to support it, but do not pack it down too much.
- Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
- Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.
Propagating Olea by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds. Seeds of Olea trees and shrubs are contained inside of the fruits that are ready for harvesting in late summer through early wintertime (depending on the species). They are ready for harvesting when they are a deep wine-red to black color and are soft to the touch. Olives will begin to drop from their attachments when they are mature.
- Seeds will need to be cold-stratified; to do so, place them in a plastic bag or other sealable container filled with moistened peat moss or sand. Place the container in the refrigerator and leave it for about two weeks' time. Remove the seeds and then take them out to work with them.
- Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Olive fruits contain seeds, also called pits.
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Olive seeds are shaped like almonds, and are brown to light brown in color.
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Problems and Pests
Olea trees are susceptible to the following pests and diseases:
- Anthracnose
- Olive Fruit Fly
- Olive Knot
- Black Scale
- Parlatoria Scale
- Apple Weevil
- Garden Weevil
- Rutherglen Bug
- Olive Lace Bug
Gallery
Olive trees are very handsome landscape trees, and are perfect for smaller garden spaces.
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The foliage on these trees is gorgeous, and adds sage-green and dark green hues to the garden.
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Olive tree bark becomes gnarled with old age, but is smooth when trees are younger.
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Videos
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Take a close look at Olive trees.
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How to grow olive trees.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 460, Olea europaea
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