AgCenter evaluating olives for Louisiana

HAMMOND – The past 10 years have seen increased interest in growing olive trees in the southeastern United States. In Louisiana, a number of individuals and businesses have planted a few olive trees. In addition to culinary and processing quality of the fruit, olives can be long-lived trees with finely textured foliage that would serve as specimen landscape trees.

The United States is the world’s largest consumer of olive oil. Currently, 99 percent of the olive oil consumed in the U.S. is imported from Italy, Greece and Spain. The fruits produce oil that contains primarily monounsaturated fats that have been determined to have certain health benefits, such as increasing high density lipid levels. Olive oil is also the oil of choice for taste and superior culinary qualities.

A few Southern universities have been working with olive trees. The South may be suited for commercial production where temperatures do not go below 10 degrees. Production of locally grown olives for oil and table use could fill a niche for a gourmet product for local farmers markets.

Olive (Olea europaea) varieties have not been university-evaluated for short-term fruiting and ornamental performance in Louisiana, so we are starting a field evaluation of 15 olive varieties at the AgCenter Hammond Research Station. This will be a long-term study with initial funding from the Louisiana Department of Agriculture and Forestry’s Specialty Crop Competitiveness Block Grant Program. The research will be monitoring growth habit, fruiting, cold hardiness, susceptibility to insect pests, dieback because of root rot and adaptation to the south Louisiana climate.

Our olive variety evaluation project will continue for the next several years, and we will provide additional information over the course of this study. We expect to hold olive growing and processing workshops as well as provide opportunities to view this research at future field days.

Olive varieties being planted include Aglandau, Bouteillan, Maurino, Manzanill, Arbosana, Picaul, Koroneiki, Pendolino, Mission, Grossane, Frantoio, Arbequina, Chemlali and Oueslati.

Olives are primarily grown for the fruit, but many varieties have considerable ornamental value in a home or commercial landscape setting. They are related to ash, privet, jamine, forsythia, sweet olives and fringe trees.

The most important characteristic for adaptation of olive varieties in south Louisiana is cold hardiness. Olive trees need cold temperatures above freezing during the dormant season to set flower buds in the spring. This is different from most other deciduous fruit trees, which set fruit buds in late summer.

The chilling requirement for olives varies from 200 to 1,000 hours. Trees are normally cold hardy to 15 degrees, although some can survive slightly lower temperatures. Olive trees are best adapted to growing conditions in south Louisiana, but some could be grown in central and north Louisiana. As trees age, cold hardiness improves.

In addition to winter growing conditions, we also must consider summer growing conditions in Louisiana. Olives struggle in periods of high humidity and frequent rainfall. Dry years in Louisiana are favorable while average-to-wet years may present disease issues.

Olives are large, evergreen shrubs under most Louisiana growing conditions, but they should be pruned to grow as trees. The fruit is a drupe. Some other flowering plants that produce drupes are jujube, mango, most palms, pistachio, almond, apricot, cherry, peach and plum.

Olives require six to eight months for full maturation. Table olives are harvested earlier, when they’re firm, and oil olives are left on trees until oil content reaches 20 to 30 percent in early winter.

Most olives are self-fruitful, but some varieties bear heavier crops when cross-pollinated. Wind is the pollinator.

Well-drained soil is very important, with sandy and silty types preferred. Trees should be planted in early spring to avoid cold damage that could occur during the winter following a fall planting. Olives need a full-sun landscape or orchard setting.

Individual trees should be planted 15-25 feet apart in a row with rows 25 feet apart in an orchard. One or two trees in a home landscape should be given space to accommodate a height of 20-30 feet with a spread of 10-15 feet.