Powerful and packed with density on multiple levels, hazelnuts are amazing. There are several species of hazelnut around the world belonging to the Corylus genus. Most species of hazelnut are shrubs, but some can be huge forest trees. Hazelnuts have been eaten by people around the temperate world for thousands of years. Pollen records show that hazelnuts were one of the first plants to appear behind retreating glaciers in a volatile and raw world. They really are rugged, adaptable survivors.
Hazels will grow in heavy clay or sand. They can tolerate drought, flooding, and a wide range of pH. They do very well on infertile soils and even better on fertile ones. They are one of the easiest plants to grow. Hazels tolerate extreme competition from weeds and even large trees. With all that said, you will get a lot more out of a hazel planting if it is well tended. As tolerant as they are of adverse conditions is also how generous they are in cultivation.
Their root systems are dense, fibrous, deep, and competitive. Stems rise out of the ground at a quick rate and are strong. They will not break from snow loads or even from occasionally being driven over.
Hybrid hazelnuts.
It is a joy to work with plants that really want to grow and require minimal care. The hazelnut is right at the top of my list of easy-to-establish, rewarding trees. Not only are they easy to grow, but the gifts that they offer are numerous and significant. From the wood to the flowers to the shells, the husks, and the nuts, the hazelnut is a powerful ally.
Species
Eighteen species of hazelnut are found in temperate areas throughout Asia, Europe, and North America. They grow in harsh and moderate conditions as varied as the Himalayas and Oregon’s Willamette Valley.
European Hazel (Corylus avellana)
These grow as shrubs throughout Europe and Central Asia. There are mountainsides entirely covered with European hazel along the Black Sea and the Caspian Sea. They are primarily gathered by hand and brought into collection points, where they are sent to large processing facilities. Around 90 percent of consumed hazelnuts come from Turkey, and this is how they are grown and harvested for the most part—in mountain culture.
Most of these nuts are much smaller than what we see in stores around the holidays. They are used for products like Nutella, oil, nut butters, desserts, and candies.
C. avellana cultivars have the largest nuts, often with the best flavor. The husks usually only come halfway down, leaving the bottom of the nut exposed.
Unfortunately, the European hazel is not very cold-hardy (somewhere around zone 5 or 7 depending on variety). It also lacks disease resistance to eastern filbert blight.
Fortunately, the European hazel has a lot to contribute to breeding programs. Other than nut size and flavor, it is also often resistant to big bud mite.
American Hazel (Corylus americana)
This extremely adaptable shrub has a range across almost all of northern North America, extending up to the tree line in Canada and Alaska. It is hardy to at least zone 2, possibly 1 in certain genetic pools. Not only are the plants hardy, but the flowers are as well. Male catkins can survive temperatures down to –50°F (–45°C), and I have seen female flowers fully open survive at –4°F (–20°C).
American hazel grows in old fields, hedgerows, forest edges, and sandy barren regions, especially around the upper Great Lakes. It forms large pure stands and thickets that can extend for many acres. It is a very tough shrub. It is just as rugged as any other shrub you’re likely to find growing in an abandoned pasture. It can reach about 10 feet high and wide at maturity.
American hazel has a big husk that completely envelops the nut. This husk is a safeguard against hungry critters. It hides the nut until after it is ripe. American-type husks offer a real sense of protection. Sometimes they are 5 to 10 times bigger than the nut inside. When they’re green, they’re full of a potent liquid that deters critters. The husks have some use in cosmetic applications.
Beaked Hazel (Corylus cornuta)
Beaked hazel has a similar range to American hazel but stretches farther west and north. Here in upstate New York, I have only found it growing sparsely in the understory. It is a smaller plant than the American. The husks also look different: pointed and very sticky with irritating hairs. Sam Thayer recommends rotting the husks off.
Turkish Tree Hazel (Corylus colurna)
Native to southeast Europe and western Asia, this is the largest species of hazel in the world. Turkish tree hazels grow up to 80 feet tall. They are sometimes planted as city street trees and in parks. They are clean, sturdy trees for urban areas. The nuts are sparser than other species. Sometimes they are of pretty good size and sometimes abundant. Often, they can have disappointingly low yields. Almost all the cultivation of this tree in the United States has centered on its landscape qualities rather than nut production.
Hybrid Hazels
Hazel species hybridize freely with one another. There have been several breeding programs that crossed hazel species. Until recently, the goal was for a plant with disease resistance, cold hardiness, and a large nut.
A lot of work was done in the 1920s to cross American and European hazels. Some of the biggest plantings were in Geneva, New York, where they completely floundered. Very few plants showed any resistance to EFB (eastern filbert blight). Some successful plants did come from some growers, including Carl Weschke and Fred Ashworth, among others. These hybrids were decent plants. Building upon their work, several more breeding programs have become well established. There are many lines of hybrids available today with very different plants.
Nuts from Jeff Zarnowski’s selection, Nitka. Jeff has planted several thousand bushes to find this one of exceptional quality. The nuts are large, have very thin shells, and taste amazing. The bush is cold-hardy, extremely productive, and disease-resistant.
The most notable hazel breeding program is at Badgersett Research Corporation. Phil Rutter (co-founder of The American Chestnut Foundation) created this program. He is a geneticist who speaks of a hybrid swarm. Hazelnuts have a huge number of genes in each species. To maximize the number of genes in a plant, Phil makes complex hybrids of three or more species. And then he grows the plants in huge numbers. A field planted with a hybrid swarm of genetics will reveal unexpected results somewhere in it. There will be plants that express traits previously unknown. This is done to find resistance to extreme weather events, diseases, insects, and the unforeseen. He has even found a few plants that make insect-pollinated flowers that are carnivorous. The hybrid swarm is a theory that aims to build resiliency into a planting during this extreme period of globalization (the movement of insects, fungi, and climate change). Badgersett’s hazels have not been bred for size of the nut or thinner shell so much as for yield (pounds per bush). They are being bred as an oil crop to cut into the vast annual tillage and cultivation of soybeans.
Many other growers in the Midwest have been breeding hazelnuts in this way. Plantings are managed as hedges of thick bushes producing lots of nuts that are not very large and have a thicker shell. Once processed for oil, butter, or kernels, it doesn’t actually matter how big the nuts are or how thick the shell was.
Nitka hazelnuts. Notice the thin shells. Photo courtesy of Jeff Zarnowski.
There are also hybrid hazel breeding programs for a larger nut with a thinner shell. These are scattered throughout the Northeast and Midwest. Jeff Zarnowski of Z’s Nutty Ridge has planted many thousands of hazels over the last 25 years and has found two exceptional plants. He calls them P-1 (P stands for “promising”) and Nitka. The nuts are large and thin-shelled, with excellent flavor. The plants are very productive and disease-resistant.
The Arbor Day Foundation and the US Department of Defense have also been researching hybrid hazels as an oil crop.
Here at my farm, I’ve been growing as many hazels from as many different places as I can, hoping to create my own hybrid swarm. I plant hybrid hazels as close as 6 inches apart, down 300-foot rows.
Cultivated Hazelnuts Around the World
Hazels are grown primarily in certain regions. Turkey grows around 80 percent of the world’s commercial crop.1 Ancient bushes grown densely on steep mountainsides are hand-harvested in the Black Sea region. One single town, Ordu, harvests a quarter of Turkey’s nuts. It is a lush pocket of land near the Georgian border. The mountains are very steep there, and at some point in history were planted entirely with hazelnuts of excellent quality. In 2013 there was a late-spring frost that wiped out almost every nut, and then it happened again the following year. The world price of hazelnuts rose from $6 to $17 a pound.2 I believe we should take this as a lesson on the value of diversity, casting a wide net, and having many baskets with lots of eggs.
Italy grows around 10 percent of the world’s hazelnuts, and they are quickly expanding.
About 3 percent of the world’s hazelnuts are grown in the Willamette Valley of Washington, which has ideal, favorable conditions for the European hazel (just like Ordu, Turkey).
All of these major hazelnut-producing regions grow C. avellana. However, a new industry is forming in the Midwest and the Northeast of the US. Hybrid bushes are being grown in hedge systems. Breeders are searching the North Woods for superior genetics, and farms are springing up at a very fast rate that appears to be accelerating all the time.
Growing Hazelnuts
Hazelnuts are a pretty easy crop to grow if you have good varieties suited to your area. Anyone in the US should use plants that are resistant to EFB.
Different growers use different techniques for spacing and pruning.
In the Pacific Northwest, hazels are grown as single-stemmed trees. Throughout the year, sprouts from the base are burned off with herbicide. Orchards are planted on level ground, or the earth is graded for flatness. The nuts are harvested when they drop from the tree out of the husk and are picked up by machine sweepers.
If this doesn’t appeal to you, don’t worry: Most other growers in the world allow hazels to be the bushes that they are. You can plant them either in a hedgerow or as individuals. Planting the bushes to stand alone, they should be spaced 8 to 15 feet apart. When planted as a hedge, 2 to 3 feet between plants and 15 feet between rows works well.
Though the plants can tolerate wet ground, they do much better when planted in well-drained soil. Since I have a clay hillside, I plant them on berms.
They can tolerate a low pH, but will do best at around 6.5. Animal manures are an excellent way to keep the pH toward neutral in a hazel planting, as they have so many other benefits. Many growers are experimenting with grazing sheep, horses, and poultry down the aisles between hazel rows. Sheep have been shown to keep the bottoms of the bushes cleaned out enough that rodent habitat is greatly reduced.
Hybrid hazelnuts growing as hedges at Z’s Nutty Ridge, McGraw, New York. Photo courtesy of Jeff Zarnowski.
To keep hazel shrubs vigorous and healthy, older stems should be pruned out. You can either remove individual stems that are over 4 or 5 years old, or coppice the entire plant every 10 to 15 years. A hazelnut left unpruned has a life expectancy of around 50 years, but regularly coppiced plants have been known to survive well over 1,000 years.
Hazelnuts will do best in full sun. They are shade-tolerant, but productivity will be greatly reduced.
Flowering and Pollination
Hazels are wind-pollinated. Each plant produces male and female flowers. The male flowers are dangly catkins. They appear in the fall and persist throughout the winter, finally opening and shedding pollen early in the spring. The female flowers are very small, beautiful pink stars that form on the tip of a bud in very early spring.
Hazel flowers are very cold-hardy. The male catkins are hardy to at least –50°F (–45°C); the female flowers on some individuals are hardy to at least –4°F (–20°C). We have had very volatile springs the last several years in upstate New York. Temperatures have swung into the 80s (27–32°C) in March some years and then back down to below 0°F (–18°C). Many plants have been blooming and emerging early only to get damaged by cold. From my observations, the hybrid hazelnuts suffer little from this. There are differences, though. Trees that are majority European heritage are more likely to lose a crop from frost. Plants with majority American genetics seem to usually come through with a lot of nuts despite the most severe of frosts.
Hazelnut male catkins in winter.
Hazels are not self-pollinating. They also will not always pollinate one another if their genes are too similar. It’s best to plant three or more and keep them close together. In Turkey two bushes are sometimes planted in the same hole to ensure good cross-pollination.
Harvesting and Processing Hazelnuts
There are two questions I hear over and over when I talk to folks about nut growing: “How long do I have to wait for nuts?” and “How do I beat the squirrels?”
Hazelnuts can start flowering as early as their first year on rare occasions. Usually they will start making a few nuts around age three to five. They can be very productive by year seven or eight.
Harvesting hazels is best done while they are in the husk. If you wait until they fall out, critters will get most of them. The bulk of my hazel harvest happens in late August, not in the fall.
Ripe hazelnuts will be fully enclosed in the husk and often still green. To determine if a bush has ripe nuts, I push on the nut. If it can move back and forth in the husk, then it’s ripe. If it doesn’t move, then it’s not ripe. It doesn’t matter if the nuts are white/green. If they can release from the husk, then they are ready for harvest.
I collect the whole husks and dry them for a minimum of a couple of weeks. Once the husks are totally dry, they will separate from the hulls much more easily. You can pull the husks apart to get the nuts. If you’re hulling a larger quantity, you can put them in a sack and walk all over them a lot, rubbing your feet vigorously back and forth. This will hull a good portion of what’s in the sack.
Hazelnut husks vary in size, shape, and color (especially among hybrids). It is satisfying work to gather the clusters of nuts.
There are many growers experimenting with different hulling machines. Most of them look something like a bucket with rubber paddles spinning around that beat up the hulls. These bucket huskers are powered by a drill. The husk pieces can be separated from the nuts by winnowing with a good wind or a fan.
Cracking hazelnuts can be done individually if you just have a few handfuls. If you want to crack loads of hazelnuts, then you will want a good cracker. There are many designs. Some shoot the nuts against a steel plate. Simpler machines involve two rotating ridged plates that pop the nuts open. The Davebilt nutcracker is a simple hand-operated machine that can crack a lot of nuts in a short time.
Once the nuts are cracked, they still need to be separated from the shell. There are two main types of separators. One uses air to blow the shells away, but since they are not lighter than the kernel, aspirators are a bit more complicated than a strong fan. Vibrating separator machines are simple but fascinating devices. Nuts are placed on a slanted tray that is shaken rapidly. Kernels rise to the top of the ramp, and shells slide down. They move in different directions based on their specific gravity. There are a lot of kinks to work out in separating nuts from shells with hazels. No one has yet figured out a truly efficient method for hybrid hazels; however, there are dedicated people working on this. If you are a tinkerer and inspired to be part of the tree crops movement, the time is ripe for you. The Upper Midwest Hazelnut Development Initiative and the New York Tree Crops Alliance are two of several organizations working on the details of processing hybrid hazels.
Pressing hazelnut oil at home with a small press. Oil is collected in the metal cup. The press cake coming out the end is mostly protein and totally dry. It is easily ground up into an excellent flour. It is hard to beat the flavor of freshly pressed oil.
Once you have hazel kernels separated, the possibilities for use are endless. They are great by themselves. The kernels are excellent in candies, especially mixed with chocolate. They can be ground into hazelnut butter. They can also be crushed and boiled to make hazelnut milk.
Roasted hazelnuts are an incredible treat. Roasting brings out the best flavor in the kernels. You can roast them in a stovetop pan or in an oven. They only take a few minutes at medium heat. Some of the native and hybrid hazels are bitter when eaten raw, but roasting them transforms this flavor into a truly excellent one.
Pressing hazelnuts for oil is one of the best ways to use these nuts. With a small home press, they need to be shelled, but with a large commercial press, they can be run through in the shell.
When you press hazelnuts or anything for oil, you will be left with the press cake as a by-product. Press cake is easily ground into flour. This is very high in protein and tastes great. If the nuts have been shelled prior to pressing, then you can add the press cake flour into all kinds of foods: cookies, granola bars, cereals, breads, muffins, and so on. If you pressed them with the shells on, then you have two options for the press cake. If some of the shells were separated prior to pressing but not all, you can still grind the press cake into flour. It takes a strong grinder, but the flour is still good; it just has extra fiber in it. The press cake is also great for animal feed, especially for poultry, who will appreciate the high protein content as well as the grit. I’ve no idea what percentage of their diet this could make up, but I’m guessing someone will be inspired enough to learn about raising poultry on press cake as more and more hazel farms get going.
Using Shells and Wood
These two by-products of growing hazels for nuts are valuable. They are actually some of the most exciting features of growing hazelnuts, in my mind.
Hazel shells are very dense. They give off as many BTUs as anthracite coal. Many modern hazel processing facilities power themselves with the shells burned in biogenerators. The shells are also sometimes used as charcoal for backyard grills. The ash from burned hazel shells is extremely high in many trace minerals, and is a good fertilizer. I believe a person could devote their life’s work to finding uses for hazelnut shells.
In Northern Europe hazels have been cultivated for centuries for their wood. Hazel canes are very strong and flexible. Wattle fences and even house walls are woven from the stems. The wood is fairly durable and makes a good alternative to bamboo canes for northern gardeners. Plants are cut to the ground on a cycle of anywhere from 1 to 10 years. Hazel wood also burns very hot and can be used as a fuel, for charcoal, or for biochar.
A by-product of pruning hazel bushes is a lot of wood. There are endless uses for this annual supply of carbon. We can use it to build soil or generate electricity or fuel vehicles. Using wood as a gas is not a new idea. In World War II, Russians converted their vehicles to run off wood gasifiers and burned sticks instead of petroleum.
Wildlife Value
Dense cover and food throughout the calendar year are what hazels provide. These are excellent plants for wildlife. Their dense thickets provide great cover for rabbits, grouse, turkeys, songbirds, raccoons, deer, and many other animals. The catkins are an important winter food for turkeys, grouse, and deer. The nuts are highly prized by turkeys, crows, jays, rodents, and foragers. Of all the different types of nuts I have grown in my nursery, none have been so marauded by wildlife as the hazel. They are nutrient-dense and the animals seem to know that.
The winter buds and summer leaves provide browse to deer. The stem bark is eaten by rabbits. Many species of native insects feed on hazel leaves. What forest edge would not benefit from the addition of a few hazel bushes?
Pests and Diseases
There aren’t too many pests to worry about with hazelnuts, but the following are important to keep in mind.
Eastern Filbert Blight
This is a native fungus that grows on hazel stems and eventually kills them. Native hazelnuts live very well with EFB. Some growers believe that EFB is mutually beneficial to American and beaked hazels because it prunes out old wood. European hazels, on the other hand, are totally killed by EFB most of the time. Originally the fungus was just in the eastern US, but now it’s been introduced out west and is a serious issue for the orchards out there.
EFB can take decades to show up. Many clones have been released that were thought to be resistant only to show susceptibility down the road. The most resistant plants come from trees with American or beaked hazelnut genetics.
Big Bud Mite
These are microscopic mites that feed on the inside of buds. They destroy flowers and leaves before they emerge, causing loss of nuts and poor growth. One control is to spray with sulfur, but this costs money, takes time, and is antifungal. I think it makes way more sense to select for resistant plants. The native hazels have poor resistance, while European hazels are highly resistant. By growing hybrids, we can find plants that are resistant to both big bud mite and EFB.
Hazelnut Weevil
These have a similar life cycle to other curculios (weevils). Adults emerge from the soil and lay eggs into immature nuts in the summer; the eggs turn into larvae that tunnel into the nut, emerge as fat grubs, tunnel underground, and then emerge the next year as adults and lay more eggs. This cycle can be broken, or at least reduced, if most of the nuts are harvested, which prevents the larvae from pupating in the soil. Reportedly, raising the pH to near neutral significantly reduces weevil populations. Beneficial nematodes are a possible option. Curculios are a challenge in many tree crops. There are species of curculio that target apples, peaches, plums, cherries, chestnuts, oaks, and many more.
A sprouted hazelnut. Watch out for birds and rodents!
Propagation
Propagating hazels is not complicated. It is limited to seed and layering for the most part.
Seed
Propagation of hazelnuts by seed is not hard if rodents and birds can be kept away. The nuts should not be dried out, but a little drying won’t hurt them. They require a cold stratification of a few months. Sometimes hazelnuts will not sprout in the spring, but wait an additional year and sprout the following spring. This double dormancy can be a challenge with many tree seeds. To avoid it, I do not plant my hazelnuts until they begin to sprout during stratification. Sharp changes in soil temperature can cause this double dormancy.
There are also germination inhibitors in hazelnuts that can be leached out to reduce the likelihood of double dormancy. This is not a necessary step, but it does seem to improve germination rates. Before stratifying, I soak hazelnuts in water for a week, changing the water daily.
Mice, squirrels, chipmunks, blue jays, and crows can decimate a bed of hazel seedlings. They will pull up plants anytime during the first season to get the kernel. You can build rodent-proof beds, eliminate habitat around a bed, or have them right next to the house where you can watch them very closely. Hazel seedlings transplant very well once started.
Layering
Hazelnuts can also be propagated by layering if you have a superior plant worth cloning. They can take two years to root if a branch is just pinned down. If you use a twist-tie to girdle the stem, they can often root in one year. Growing hazels in layered stool beds is how they have traditionally been propagated for orchards. Today they are often being produced in tissue culture.
Creating Change
Hazels provide food, gather carbon, build soil, increase wildlife habitat and diversity, can be used for windbreaks, and are grown for their wood. These plants add strength to the world. If you care about food justice or climate change or wildlife, then hazelnuts are your allies. They will do the work willingly and very well. These spreading bushes are providers. While annual agriculture supplies us with abundant food, it also erases the landscape every year and burns up the carbon in our soils. Hazelnuts are a force that is far more effective than any vote or dollar in creating the change we want to see.