Olive trees are a pretty frequent sighting around here. I think their silver leaves look really nice in a landscape, but I’ve largely ignored them since I didn’t think they would grow in any climates below zone 9, and you can’t eat the fruit (olives) without processing them first, which seems like a lot of work.
Well…you better believe that Oregonians are trying to change that.
I’m general, olive trees don’t do well below 13 degrees F, and the fruit, which takes a long time to ripen is damaged below 27 degrees F, so you need very long summers in order to get a decent harvest. Also, olive trees grow best in dry, hot climates, not the wet climate of the Pacific Northwest.
But some varieties are hardier and/or ripen faster than others. Frantoio and Arbequina are two hardy olive varieties that were mentioned a few times in my research on olive trees that can supposedly withstand a zone 8 climate.
As it turns out, the last time the temperature dropped below 13 degrees F in downtown Portland, OR was 1990, so if you have a favorable microclimate in your yard, and had a hardy variety, I’d think an olive tree would have a shot. Ideally, you would plant the tree in an area that is sheltered from wind, gets a lot of sunlight, and is situated on well-draining sloping soil. From what I read, you should try to plant olives in spring so that they have a chance to get established before they are tested a cold, wet winter.
As for processing the olives, Rosalind Creasy says in Edible Landscaping, “I cannot with good conscience urge you to try preserving olives yourself. The standard procedure for removing the bitterness from the fruits requires that they be soaked in a lye solution….However, pickled olives and olive oil are less hazardous to produce. Olive presses are available for making olive oil at home….Although admittedly olive oil is a chore to produce, the superior product and the resulting money savings for heavy users make the effort worthwhile.”
You can supposedly pick green olives to make olive oil as early as September, which means the olives wouldn’t be at risk of being damaged by a cold freeze in Portland. Olives fully ripen between October and December.
While olive trees are self-fertile, having two varieties can improve yields. Supposedly, the Frantoio and Arbequina trees can produce over 20 lbs of fruit each, which is enough to make 3 liters of olive oil, so from these two trees, you could theoretically get about 1.5 gallons of olive oil each year, which averages out to about 1 tablespoon of olive oil per day over the course of a year…is it worth it to try to grow olive trees in Portland?