Jennifer Schultz Nelson
Extension Educator, Horticulture
Olives (Olea europaea) are more popular than ever. I grew up thinking there were two kinds of olives: the green ones with red pimentos in the center, and black ones. Boy was I wrong!
Growing up we were not a big olive-eating family. I can probably count on one hand the number of times I remember my mom buying olives. It wasn't until I was in college that I developed a taste for olives, but only the black ones, and only in certain dishes, like pizza.
Early on while dating my husband, we went out for a nice dinner, and along with the bread basket, the restaurant brought roasted garlic and olives to the table. These were not the green or black olives I was used to seeing. These were kalamata olives, a dark brown color, and as I was soon to find out, they also contained pits.
Each of us took an olive and not only was there a pit in the center when I bit down, it also tasted horrible to me, kind of like dirt combined with old socks. I know some of you probably love kalamata olives, but I couldn't figure out at that point why anyone would voluntarily eat them.
I somehow swallowed that bite, and looked up to see a pained expression on my now-husband's face. He didn't like them either. We were both just trying to be polite! The whole scene dissolved into laughter, and we don't worry about being honest about foods we do or don't like anymore.
Despite my opinion of the flavor of some olives, I think they really are an interesting fruit. They have a very rich history, and have been mentioned in the holy writings of Judaism, Christianity and Islam. Olive branches are even on the back of the U.S. one dollar bill–look closely at what the eagle on the back is holding in his talons.
Olives grow on trees native to the Mediterranean, parts of Africa, and Asia. While they tend to grow best in temperate areas near water, there are some inland areas that can support good growth of olive trees. Cultivation of olive trees occurs in their native lands as well as South America, Australia, and in the U.S. in California.
Olive trees generally achieve a mature height of 25 to 45 feet. Trees that are being used for olive production will typically be pruned to be much shorter so that the fruit can be harvested easily. The leaves are lanceolate, waxy green on top and a grayish green underneath. The tree itself usually grows in a gnarled and twisted shape.
The olive tree is a very slow grower, but can live an extremely long life. There are specimens in the world today that are well over one thousand years old that still bear fruit! Even when the upper portion is damaged, olive trees can regenerate from the roots. It may surprise you as it did me, but a lot has to happen to an olive before it reaches our table.
There are two basic types of olives, just like I thought years ago–green ones and black ones. The green ones are not ripe, and the black ones are ripe. Different types of olives come from not just different olive cultivars, but from differences in how they're processed for table use.
Fresh-picked green olives are not fit for human consumption. They are extremely high in a glycoside called oleuropein. Chemically, a glycoside is a molecule with a sugar molecule attached to it. You might think this chemical would be sweet but it's not. It's extremely bitter.
One way to remove the bitter oleuropein is to soak the olives in lye, a source of sodium hydroxide. Then they are washed thoroughly to remove all traces of lye. Black olives would be then ready to eat, but green olives are typically subjected to fermentation following the lye treatment. Some sources say black olives don't need lye treatment, others do. It probably depends on the type of olive and your taste buds.
Older olive processing methods do not use lye, but instead use fermentation to remove the bitterness, which takes longer. Whether treated with lye or fermented to remove the bitter flavor, green olives are typically fermented further to develop different flavors. When fermentation is completed, the olives are typically cured in brine (salt water), salt, or oil where they can be stored for months. Other ingredients may be added during this process such as herbs, spices, wine, garlic, vinegar, or salt. Sometimes the green olives' pits are removed and the olive is stuffed with ingredients like pimento or cheese.
This long process eventually produces a food product eaten around the world. Amazingly, olives harvested for table use are still picked by hand. Those destined to be pressed for oil are shaken from the trees by mechanical shakers and collected in a catcher that looks like an upside-down umbrella.
While we cannot grow olives outdoors in central Illinois, you can grow them outdoors in containers that you overwinter inside. I found one for sale recently, and am excited to see how it does on my patio this summer.
There are some plants in our landscape that we commonly call Russian Olive (Elaeagnus angustifolia ) and Autumn Olive (Elaeagnus umbellata), but they are not true olives. Their fruits are edible, and at points in time both of these species have been cultivated in the landscape, being useful as quick-growing windbreaks. But in some areas, central Illinois being one of them, one or both of these species have spread across landscapes and become a nuisance.
The interstate highway is a good place to spot these trees. Russian or Autumn Olive trees are a distinct sage green, and typically grow in thick masses, sometimes looking more like bushes than trees. If you've tried to remove one of these trees, you know it can be very difficult. We had one on the shore of the pond behind our house, and it took several treatments with brush killer on the stump before the roots completely died. These trees tend to produce thousands of fruits with viable seeds, so it's likely I'll be removing this tree's descendants in future years.