The olive is an exotic fruit crop in Texas. Olives are native to the Mediterranean Basin, which usually has mild, rainy winters and hot, dry summers. In contrast, Texas sometimes has severe winter freezes that can kill olives to the ground. The best area in Texas to attempt commercial olive production is in the southwest region north of Laredo and southwest of San Antonio (known as the Winter Garden, also our area).
The late Earnest Mortensen of the Texas Agricultural Experiment Station brought olive trees to the Winter Garden in the 1930s. Some of Mortensen’s trees survive today. Although research by Texas A&M University has indicated that olives could be grown for fruit production in large parts of East, Central, and South Texas, those studies also found that growers should expect severe winter freezes to kill trees to the ground about three years of every 10. Over the past 10 to 15 years, olive plantings have increased in Texas, primarily southwest of San Antonio and in the Hill Country. Not all of these plantings have been successful. Extreme South Texas does not typically experience enough cool weather for the olive to set fruit. There, it may be grown as an ornamental. Can they grow in Victoria County? Currently, Victoria County has about 800 acres in olive tree production with more slated to plant.
In Texas, ‘Manzanilla’ olives are primarily pressed for oil. The olive is related to the desert olive (Forestiera sp.) and the American wild olive (Osmanthus sp.), which are not edible. It should not be confused with the Russian olive (Elaeagnus angustifolia) or the anacahuita (Cordia boissieri), which is sometimes called the Texas or Mexican olive. These plants belong to different botanical families.
The best olive production and quality occur where conditions are similar to those in the Mediterranean: mild winters and long, warm, dry summers. The tree’s growth begins in the spring after average temperatures rise to 70 and continues until temperatures drop below that point in the fall.
Unlike many other temperate fruits, olives are evergreen trees that do not experience a winter dormancy period. Olive trees freeze in extreme cold. For the above-ground portions of trees to survive, they must be protected, especially during the first three years of establishment. Their cold hardiness is like that of citrus, improving with tree age and increased trunk size: Young trees may be killed when the temperature drops below 25. Freezes in Texas are unpredictable – they can occur unexpectedly in the fall, spring and winter. The survival and extent of freeze damage of olives depend on several factors, including seasonal timing, warm versus cool day/night temperatures before the freeze, and the depth and duration of low temperatures experienced. Less damage occurs when the temperature decline is gradual rather than sudden and steep. The tree’s winter survival can be affected by late summer and fall growing conditions. Trees may be more likely to sustain freeze damage if they were given too much water and fertilizer late in the growing season, causing them to continue growing too long. Mature trees can regrow from the underground crown after a severe freeze.
Once established for three to five years, olive trees become more resistant to freeze damage. However, they can lose their cold hardiness when temperatures fluctuate in the winter. In many areas of Texas, temperatures can rise to the 60s in January and upper 80s to 90s in February, only to be followed by severe cold in March. This pattern may result in severe tree damage or death.
Fruit set can be seriously hampered by rain, near-freezing temperatures, very high humidity, and/or hot, dry winds during bloom in the spring. Unlike most fruit trees in Texas, the olive does not set fruiting buds in the fall. Instead, the tree sets flower buds during the winter only after being exposed to cool nights (35 to 50) and mildly warm days (less than 80). This warm day/cool night exposure is called vernalization; varieties differ in the temperature ranges required. Only perfect flowers can become fruits. Bees and other insects play a minor role in olive pollination; wind moves most of the pollen from tree to tree. Although most olive varieties are self-fertile, some varieties are naturally incompatible, requiring cross pollination with another variety to set fruit.
Olive trees grow in a wide variety of soils, from sands to clays, and the pH ranges from 5.5 to 8.5. They also have better tolerance to soil and water salinity than many commercial fruit crops. Because olive trees have fairly shallow root systems, the soil need not be deep.
However, it must be well drained. Clay or rock layers and/or different soil textures can hinder water drainage and cause the olive trees to drown out. Of concern are not the dry periods but rather those when the area gets an abundance of water from either irrigation or rainfall.
If the groves remain saturated for an extended period, the trees may die.
More research needs to be done on olive production in this part of the state before we consider this a viable crop alternative. However, many varieties do show promise.
SOURCE: Texas Fruit and Nut Production: OLIVES, Larry Stein, Jim Kamas and Monte Nesbitt, Extension Fruit Specialists, Texas A&M Agrilife Extension, Texas A&M University System