LSU AgCenter Horticulturist
(09/20/19) Olive trees (Olea europaea) are some of the oldest trees cultivated by humans, having been grown as early as 2500 B.C. in Crete. The typical lifespan of an olive tree is 300 to 600 years; however, some trees have lived more than 1,000 years. In fact, some olive trees that still bear fruit are said to be more than 2,000 years old and still growing in the Garden of Gethsemane (Hebrew for “olive press”) at the foot of the Mount of Olives in Jerusalem. Olives have been mentioned in historical records for thousands of years.
Over time, an olive branch has become a universal symbol of peace, mainly due to the Bible story of Noah sending a dove after the great flood and having it return with an olive branch that provided evidence that plants were growing again. Ever since, olives have symbolized the hope for a peaceful future.
Olives are an important crop globally. The trees produce edible olives and oil that also can be used for skin and hair care. In ancient times, olive oil was the fuel used to light the golden menorah in the ancient temple in Jerusalem and oil-burning pottery lamps.
Olive oil and olives have antioxidant and anti-inflammatory properties, the health benefits of which have long been touted. Olive oil contains 14% to 15% saturated fat, and 11% to 12% is polyunsaturated omega-6 and omega-3 fatty acids. The main fatty acid is an oleic acid, a monounsaturated fat that makes up the remainder of the 73% of the oil content. It is these fatty acids that provide its health benefits.
Olive trees typically grow in warm, dry areas. They are native to Mediterranean climates that have hot, dry summers and mild, wet winters. According to the International Olive Oil Council, global production in 2017-18 was 3.65 million tons of olive oil and 2.91 million tons of table olives.
In the United States, olives grow well in California, which has 35,000 acres in production and is the largest domestic olive producer. The industry has made its way south to Georgia, Florida and Texas. Currently, no major commercial production is in Louisiana, although some olives are planted on urban farms and in home gardens.
Three olive trees are on the main campus of LSU behind Wilson Hall. Horticulture instructor Bob Mirabello planted these trees at the LSU Hill Farm in 2008. They were relocated to Wilson Hall nearly seven years ago. Despite being moved, they have thrived and have never suffered any cold damage. Today, the trees are full of fruit and offer a gorgeous display.
The LSU AgCenter has conducted some olive research at the Hammond Research Station, which dedicated an acre of production to nearly 100 trees of 15 different varieties for evaluation. The top-performing varieties are Anglandau, Arbequina, Bouteillan and Picual. Other varieties — including Grossane, Manzanilla, Arbosana, Frantoia, Koroneiki and Mission — suffered split bark and excessive leaf loss during an extended hard freeze in January 2017.
Olive trees prefer well-drained soil due to their shallow root system, but they can tolerate very low fertility soil and bouts of drought. They are considered evergreen tropical trees and will grow in USDA hardiness zones 8 through 10 to a height of 20 to 30 feet and width of 15 to 25 feet. They have an inconspicuous but fragrant white flower in June and July that form showy, edible fruit in early fall. Olive trees prefer full sun, have a medium maintenance requirement and can tolerate drought once they are established. There are no serious insect or disease problems. However, olive knot, verticillium wilt and root rot have been reported in some plantings.
Olive trees are winter-hardy down to 10 to 15 degrees Fahrenheit and will overwinter well in protected areas around buildings. In north Louisiana, they can be grown in containers and protected during extended low temperatures. However, like most other fruit crops, they require chilling hours of at least 80 days at 30 to 42 degrees to get adequate flower and fruit set in the summer. Mild winters like those in south Louisiana can cause poor flowering and fruiting due to insufficient chilling temperatures.
In addition to being a valuable fruit- and oil-producing crop, olives are also valuable from a landscape perspective. Some of the characteristics that make this plant interesting for landscapes are its simple elliptic leaves that display a green-blue-silver color year-round. They do well in containers in colder climates and can serve as windbreaks. They also can be planted closely together to create a screen. Olives have a neat and clean growth habit that does not require cleanup. Young trees have smooth gray bark, but as the trees age, the trunks and branches grow gnarly, giving it its distinguished and symbolic growth form.
Olive trees have a rich story in human history. This tree has been central to Spanish, Italian, Greek, Israeli, Jewish and many other cultures. It has become a symbol of strength and resiliency because the trees have stood the test of time, surviving for thousands of years. They are able to tolerate poor soils yet still produce large amounts of fruit and oil. A single tree can produce up to 20 gallons of oil per year.
The wood from the trees has been used to build homes and ornamental artifacts important to many cultures globally. When the ancient temple stood in Jerusalem, its beautiful wooden doors were built of fragrant olive wood. I display spiritual artifacts in my home from the Holy Land that are made of olive wood. It’s amazing how this plant touches so many lives.
When I sit back and think of how important olives are to our world, I cannot help but take notice of how important they are to me personally. I named my daughter Olivia after olive trees because of my love of horticulture. I wanted to carry on the tradition that my mother began when she named me after the heather flower. My husband chose our second daughter’s name — Hadley, which means “field of Heather.”
Isn’t it amazing? We all have a story. We all have a history. And we all are connected.
Olive trees grow to a height of 20 to 30 feet and width of 15 to 25 feet. Photo by Heather Kirk-Ballard/LSU AgCenter
Olive trees provide gorgeous display of showy, edible fruit and simple elliptic leaves that display a green-blue-silver color year-round. Photo by Heather Kirk-Ballard/LSU AgCenter