Plant an Olive Tree
It’s no news that Marin, Sonoma, and Napa boast a magical alchemy of sun and soil for the edible gardener. Not only does our kind California climate coax a year-round bounty of fruits and vegetables from our very own garden plots, but our mild winters offer a unique opportunity to grow luscious Mediterranean crops like grapes, pistachios, figs, citrus and pomegranates. The star of this group that has it all—exceptional fruit, evergreen good looks, easygoing needs, and mind-boggling historical significance— is the olive tree (Olea europaea).
The olive is one of the oldest crops in the history of humankind. Over 7,000 years ago, people began cultivating these elegant trees. The love affair evidently continues today, as the olive ranks as the single most cultivated fruit crop in the world. Its historical impact is undeniable. The ancient Greeks honored it as a symbol of prosperity and triumph (think victory crowns at the Olympic Games) and Homer regularly cited it as a pivotal plant in the twists and turns of The Odyssey. Olive trees are mentioned over 30 times each in the Bible and the Qur’an. Talk about longevity, these spiritual trees can thrive and produce olives for an average of four centuries! The oldest olive tree alive today resides in Crete and is estimated to be 3,000-5,000 years old. But what can an olive tree do for you in your humble home garden? With just a single tree and a willing nod to the Six P’s—planting, pairing, pruning, pests/pathology and picking— you will be rewarded with plentiful fruit on a handsome tree that is built to last.
When shopping for olive trees, it’s imperative that you choose one with a supremely even canopy. This translates as the lack of a “dominant leader,” or upward-growing branch that would otherwise lend the tree a lopsided appearance. Ultimately, this perfectionist purchasing moment will prove literally fruitful. Equally important is a plant with solid green coloration and a root system that just holds the soil together when gently tugged from the pot.
Petaluma’s McEvoy Ranch grows and sells a wide variety of exceptional organic olive trees at the ranch on Red Hill Road, their retail location at the San Francisco Ferry Plaza Marketplace, various local farmers’ markets and online, so it’s no wonder that the Nursery and Vineyard Manager, Samantha Dorsey, is an olive tree guru. Her words of wisdom, coupled with the visual aid of a precise planting illustration included here, make the following musts utterly clear: plant in a wind-free, full-sun location in well-draining soil; mix an organic, balanced, pellet fertilizer into the planting hole, then fertilize again every fall and spring; support the trunk by using a stake or two; and—the most important detail—plant the crown of the tree (top of root ball) exactly at the soil level in a pot or atop a mound you have created if planting in the ground. If you plant it too deeply or if you carve out a water-collecting basin around the trunk of the tree, you may set up rotting issues.
While olive trees are genetically drought tolerant to some degree, they are healthier and more productive when watered regularly and deeply. Optimum frequency varies with soil type and location—pot-grown trees and loamy soil dry out faster, for example—so irrigate based on how the soil feels when you poke your finger into it: add water only when it gets crumbly and is starting to dry out.
Many gardeners adore the olive’s leafy good looks but don’t care for the fruit which will drop and create a mess if you do not formally “harvest” them. If this is you, track down a fruitless variety like Swan Hill or Wilsonii. But, if you’re an olive addict like myself, you’ll be pleased to discover an abundance of varietal options. Cramped gardens that can afford only a single tree should stick with a self-pollinating varietal like Frantoio or Arbequina. Those who fantasize about endless winter-noshing on homegrown table olives should plant the tremendous trio of Frantoio, Maurino, and Leccino. As long as they are planted within the same 100 yard area, this pollination party will yield literal bucketfuls of olives from each tree.
I am always surprised to learn that even the most seasoned home gardener is intimidated by pruning. If a thriving olive tree is your quest, then it’s time to transcend your cutting fears because, just like roses, olives absolutely require significant pruning in January or February. Olive trees pruned to have an “open-vase” shape yield the most fruit for two reasons: air circulation keeps the foliage and fruit free from fungal foes and light penetration encourages maximum fruit set and even ripening. This moniker is literal – the perfectly pruned tree should look like an open vase.
To achieve this, the first line of attack is to avoid “apical dominance,” or the growth of a main, central branch that is dominant over the side branches. You do this by pinching out the top of the plant to encourage the growth of lateral branches. Some gardeners might think of this as “topping.” For young, vigorous trees, pinch out the apical stem twice a year; on older trees (5 years and older), once a year will suffice. Regular sucker removal from the base of the tree is a must as well.
The finer details of pruning may sound abstract via the written word, but a year or two of hands-on haircuts will demystify the process. As long as you remember a few key concepts—year-old wood, fruiting umbrella, undercutting, and thinning—it will become second nature in no time. It’s imperative to remember that olive trees fruit ONLY on the previous year’s growth. Thus, removing year-old wood literally tosses away the fruit buds. The goal is to create an “umbrella” of fruiting wood on the outside of the tree and to remove dead and leafless branches from the inside of the tree. This type of pruning is called “undercutting” and it differs from typical pruning, which entails cuts made on the outward-growing branches. As for thinning, sometimes you may need to remove entire branches, sometimes less. You want sunlight to reach the inner branches. To illustrate, Dorsey shared these helpful European anecdotes: The French say that a little bird should be able to fly through an olive tree without clipping its wings and the Italians say that one should be able to see a naked lady through the branches. In other words, thinning is real and necessary. Snipping here and there won’t suffice. If all else fails, you can run up the white flag and contact Dorsey by email at Samantha@mcevoyranch.com.
Dorsey offers a final excellent pruning-like tip for the first year of planting: regardless of the size of the tree, strip it of every flower so the plant can devote its energy to vegetative growth and settling into its new spot.
PESTS AND PATHOLOGY
In 1998, California’s olive farming changed forever with the arrival of the olive fruit fly. This devastating pest injects eggs into the fruit which is then destroyed by hungry, tunneling larvae. It poses such an acute economic threat to California that commercial growers respectfully ask home growers to take the problem seriously. If you don’t plan on harvesting the fruit, then either grow a fruitless variety or knock off the blooms. And if you do want the bounty, commit to monitoring and controlling these pests by hanging one McPhail trap (baited with torula yeast) or other similar device for every one to two trees. Gardeners with more than 25 trees should invest in the natural insecticide Spinosad. You can find both of these products at Harmony Farm Supply & Nursery of Sebastopol and many other local nurseries. Note: The experts at Harmony urge spraying Spinosad only after dusk to reduce the risk of harm to beneficial insects and bees.
Olive trees are also prone to several fungal diseases that are challenging to combat and, if left unchecked, may lead to eventual demise. “Crown Rot,” or the rotting of lower tissue, is caused by planting too deeply and overwatering. Attentive gardeners can easily avoid this problem. “Verticillium Wilt” is a fatal foe that manifests as the sudden browning of all the leaves on a single branch. It’s probably worth ditching the tree and planting a new tree in another spot if you have a tree which develops this. “Peacock Spot” which manifests as circular spots on the foliage is quite common and treatable. Although this disease does not attack the fruit, it will eventually distress the foliage to the point that the tree itself will struggle to survive. Regular applications of copper oxide immediately after harvest (but before the first rain!) will keep this problem in check. On a lighter note, yellowing leaves signify a nitrogen-deficiency that is easily treated with liquid seaweed or fish emulsion three times a year.
You’ve planted and pruned and dealt with pests and pathology… now it’s time to pick! In Northern California, harvest runs from November to January. If you plan to brine the fruit into delectable table olives, start picking in November when the flesh is firmer, beneficial polyphenol levels are highest and flavor is most pungent. It is a common misconception that some trees bear green olives and some trees bear dark purple or “black” olives. All olives start out green and ripen to the dark purple color. The greener, or less ripe the olive, the more piquant the flavor. As olives ripen and turn to dark purple, the polyphenol levels drop and the fruits mellow to a classic, buttery, black olive flavor. That’s the time to pick for oil.
Begin picking green olives when the fruit feels only slightly soft and a tad oily. Lovers of green olives can pick them all at once. For a spectrum of colors and flavors, harvest every few weeks. The chefs at McEvoy Ranch have perfected brining into a rustic science and they’ve kindly shared the recipe found here for home cured table olives. If you fantasize about turning your fruit into oil, keep in mind that a seven-year-old tree produces roughly 40 pounds of fruit. While that’s ideal for curing, it’s slim pickings for oil, morphing into a preciously petite half-gallon.
That said, you can still embrace the collective oil-pressing spirit by joining in the fun community press days held at various olive oil producers in our area including Dry Creek Olive Oil Company in Healdsburg (www.drycreekolivecompany.com ), Frantoio Olive Oil Company in Mill Valley (www.frantoio.com ), Long Meadow Ranch in St. Helena (www.longmeadowranch.com ), McEvoy Ranch in Petaluma (www.mcevoyranch.com ), and The Olive Press in Glen Ellen (www.theolivepress.com ).