I once grew a trio of hazelnut trees on my property in Pennsylvania, planting them in a triangle 15 feet on a side that surrounded a large rock about the size of a VW Beetle. One year in late August, when they were about 5 years old and 15 feet tall, their tops reached each other and made a canopy that shaded the rock.
This was the time in late summer when filberts, as hazelnuts are also called, are ripe enough to be picked, so I took my six-year-old daughter and a large woven white-oak basket to the tall bushes to go a-nutting, as country folk used to say.
“Do you see any nuts?” I asked her. She looked all around, but after a few minutes declared that there were no nuts. Sensing that this was a teachable moment, I told her we had to sit down and wait patiently, and eventually the nuts would appear. She looked at me skeptically. After a few more minutes, though, she saw one—or, rather, two fringed, green husks in which the nuts reside, hanging like a pair of narrow-mouthed bells just under a clutch of leaves. And then she saw another. And then another, until finally she saw that the bushes were loaded with nuts.
Unfortunately, the squirrels also had no trouble seeing the nuts. And for the next couple of years, they beat me to the crop, literally stealing every last nut. Frustrated and angry, I took my .22 rifle and sat on the rock. I remember what I shouted: “Okay squirrels, listen up! You see this rifle? If you swipe all these filberts, I’m going to shoot you dead. But I’ll make you a deal. If you leave me at least half the nuts, I won’t shoot you. Guaranteed!”
To my surprise, it worked. From then on, we had plenty of our own sweet hazelnuts and so did the squirrels. Those trees—by then they were tall and rangy, maybe 20 feet tall or more—bore magnificent crops. My half of the crop filled the oak basket every year.
Imagine my delight then, while walking down my quarter-mile-long rocky driveway, I noticed bushes along the side that looked very much like my hazelnuts, only in miniature, just four feet tall. On closer inspection, I could see little husks and nuts hanging among the leaves and branches. I’d discovered the wild hazelnut, Corylus americana, growing right on my own property.
But there’s always trouble in paradise, it seems. Those wild hazelnut bushes are host to a fungus, Anisogramma anomala, commonly known as eastern filbert blight, that doesn’t do much damage to native wildings like C. americana and the Western-native beaked hazelnut, C. cornuta, but aggressively destroys the commercial nut-bearing hybrids, usually within 10 years. They are hybrids of the northern European native C. avellana and southern European C. maxima. As European natives, they didn’t co-evolve with the filbert blight fungus and have no natural resistance. The blight also attacks C. avellana ‘Contorta’—or Harry Lauder’s walking stick—a twisty, curvy ornamental that I also grew in my Pennsylvania landscape.
I never saw blight on either my nut trees or Harry Lauder, but I moved to California about the time the filberts reached 12 years old and were due for infection. On a return visit to the property about a decade later, the filberts I’d planted were gone, but the wild bushes along the driveway were charming as ever.
Fighting the Blight
Whether you call them hazels or filberts, they grow wild and as cultivated varieties almost everywhere across North America. In fact, the commercial hazelnuts we find in stores are mostly grown in Oregon and Washington on the same hybrids I’d planted in the Mid-Atlantic region. Oregon’s Willamette Valley produces about 98 percent of the filberts in commerce in the United States.
Unfortunately, eastern filbert blight has now made its way to the Pacific Northwest and it is attacking the major plantings in the Willamette Valley. Growers estimate that yields will be down about 20 percent this year, due to the need for pruning out infected wood. Unlike most fungi that attack woody plants through wounds in the bark, EFB, as it’s known, infects new growth, especially as the shoots are elongating in the spring. It’s spread by raindrop splash, wind and by the orchardist who isn’t careful about disinfecting his or her tools, or disinfecting hands after touching infected wood.
There is no cure for EFB. If you want to plant for nut production, search online for the cultivars of nut-bearing resistant hybrids called ‘Jefferson’, ‘Santiam’, ‘Yamhill’ or ‘Theta’. ‘Red Dragon’ is a resistant ornamental cultivar. Dr. Thomas Molnar at Rutgers in New Jersey is doing good breeding work for resistant cultivars. The hazelnut-breeding program at Oregon State University, directed by Dr. Shawn Mehlenbacher, uses the genetic diversity in the genus Corylus to create new EFB resistant cultivars for the Oregon industry. The cultivars 'Lewis', 'Clark', 'Gem' and 'Sacajawea' show good resistance across several genes, while 'Santiam', 'Yamhill', 'Dorris', 'McDonald' and 'Jefferson' have a single dominant resistance gene. ‘Jefferson’ especially shows promise. It may develop a few stromata (spore-producing black fungus patches on the bark) but not enough to kill the plants. And the stromata tend to disappear after a few years. Still, it will be wise for those who plant ‘Jefferson’ to prune out infected branches because they may spread the disease.
EFB kills by girdling the bark and destroying the cambium. It doesn’t infect the leaves, flowers, catkins or nuts, however. The best time to check your filberts for infection is winter, when the leaves are gone and the bark can be easily looked over. The fungus produces black, rough patches in discrete lesions on the bark, especially on young wood. If you find some infected branches, prune them two to three feet below where you spot the first canker. Disinfect your pruners in 10-percent bleach or 70-percent alcohol solution between cuts, allowing them at least 30 seconds in the solution and letting them air dry. Pruned branches should be burned, buried deeply in a pit or chipped and allowed to dry well before burning or removing. Make sure you aren’t transferring fungus on your hands or clothes as you do this work. If a filbert is so badly infected that it would need too heavy a pruning, remove the whole plant. Don’t be shy about being relentless with this disease.
Other than the blight problem, filberts are one of the easiest nut trees to grow. They prefer well-drained soil of moderate fertility. Too rich a soil produces an abundance of wood and leaves and sparse flowering. They spread by underground roots, sending up many suckers, and so if you want them as a single-trunked tree, you’ll have to keep cutting off the extra shoots and suckers that arise each year from the roots. Nut production is best, of course, if you let many stems grow into trunks with fruiting branches.
Filberts develop a taproot as well as underground runners, so after about three years they don’t like to be moved. Taproots also don’t favor constricted containers, in which they will just curl around and around, so filberts aren’t plants for growing in pots.
Prune to keep the stand open and airy, especially if allowing plants to become multi-trunked. Breezes facilitate pollination. If you’re planting more than one cultivar, make sure your choices’ catkins are shedding pollen at the same time flowers are opening. Remove trunks if the stand becomes too crowded, with lots of crossing branches. Take out whole suckers and trunks; don’t cut back the upright shoots. Plant in full sun, although they will tolerate partial shade if it isn’t too deep.
Harvest and Enjoy
Harvest the paired husks and nuts when ripe, around Labor Day. Spread them on a tarp where squirrels can’t get at them and shell the nuts out of the husks as you find the time. When first harvested, the nuts inside their shells are unpleasantly moist and need to dry out over the next few months, a process called curing. My home-grown filbert nuts invariably developed a little greenish mold on the more porous part of the shell as they cured during September through November and moisture escaped, but I never noticed that there was any loss of quality in the nuts inside. I believe the small amount of mold was just on the surface of the shell. Commercial hazelnuts are given a mold-prevention treatment with sulfur dioxide. If you want to prevent mold on your homegrown nuts, buy a bottle of Campden tablets at your winemaking-supply shop (or online). Dissolve a couple of 50-mg tabs in a quart of water, then dip the nuts in the water, let them dry and they’ll be mold free. The tablets release sulfur dioxide that kills mold spores.
Hazelnuts are champions when it comes to percentage of monounsaturated fat. Nearly 80 percent of the oil is monounsaturated. Gourmets use the expressed oils for salad dressing. A little goes a long way. The delicate flavor of the oil is quickly ruined by heat, so it’s not an oil for cooking. And it tends to go rancid quickly, so buy it in small quantities.
To get the best flavor, lightly roast the shelled nuts. Their flavor harmonizes well with coffee and chocolate—although I don’t like the so-called hazelnut-flavored coffee that tastes like a chemical analog to the real thing. I do like the ground hazelnut and chocolate spread called Nutella (but who doesn’t?).
In the fall, after they’ve cured, you can store them in the freezer for up to a year, so you can always have fresh-tasting nuts. You’ll find that a pound of hazelnuts in the shell equals about a cup and a half of shelled nutmeats, and that one cup of whole shelled nuts is about five ounces. My favorite way to use them is as a hazelnut torte. Use only hazelnuts put through a hand-cranked nut shredder, and flavor it with melted dark chocolate. Serve a slice with a cup of espresso. That’s perfection.
Jeff Cox gardens in the Sonoma Valley of California.
Image credit: Fabio Pagani/EyeEm/Getty Images