The Amazing Hazel - The Essential Guide to Probably Everything you Need to Know About Growing Hazels - Corylus spp.
Hazel is a multi purpose champion of a plant that is super easy to grow, produces delicious nuts, pliable wood that can be crafted into a variety of products, provides early fodder for bees and an encouraging spectacle when flowering during the mid winter. What more can I say…. a plant so good people started naming their daughters after it.
During this post we’ll take a close look at these versatile plants, including how and where to grow them, growing them in polycultures, how they can be used in agroforestry systems, coppicing hazel, and end the post by introducing some hardy productive and disease resistant cultivars that we are offering from our nursery.
When we speak of Hazel we are generally referring to two species, Corylus avellana and Corylus maxima. The two species produce slightly different shape nuts and take different growth forms. Corylus avellana produce Hazelnuts and Corylus maxima produce Filberts. There are 14–18 species in the Corylus genus but many of the European cultivars we have nowadays are Corylus avellana, Corylus maxima or the result of hybrids between these two species. This post we will focus solely on these popular nut producing species.
Overview
Latin name — Corylus avellana, Corylus maxima
Common name — Hazel, Hazelnut, Cobnut, Filbert, Spanish Nut, Pontic Nut, Lombardy Nut.
Family- Betulaceae
History — Pollen counts reveal that Corylus avellana was the first of the temperate deciduous forest trees to immigrate, establish itself and then become abundant in the post glacial period. Humans have been enjoying hazels since prehistoric times and it is thought by some that hazelnuts provided a staple source of food before the days of wheat. Evidence of large-scale Mesolithic nut processing, some 9,000 years old, was found in Scotland and Hazels have been used extensively across the temperate zone throughout all civilizations.
Description — Corylus avellana — Grows as a small tree or large shrub commonly reaching heights of 5 m with a 5 m spread, but sometimes can reach twice that height and takes a tree like form. The leaves, that open in late April and May and fall in November, are almost circular with double toothed edges and a short pointed tip. The leafy bracts are shorter than the nut.
Description — Corylus maxima — Grows as a large shrub 6 m high with a 5 m spread. Resembling C.avellana but with young grey twigs, glandular and bristly leaves that are wider, longer catkins and leafy bracts that are tubular and closed twice the length of the nut. The nuts are also longer than C. avellana
Both species are monoecious . The male flowers are encased in catkins that brighten up the landscape in the winter. The female flowers are tiny red tassels that emerge from buds on the stems.
Sexual Reproduction — As mentioned above the plants are monoecious, producing male and female flowers on the same plant. The male flowers are held in catkins that form during the previous summer and open in the dead of winter and flower through to early spring. There are around 240 male flowers in each catkin and these produce the pollen. Give the catkins a flick in late February to see a small cloud of pollen erupt. Contrary to the wonderful spectacle of the male flowers, female flowers are almost invisible unless you are actively looking for them. They are tiny individual flowers, visible only as red styles protruding from a green bud-like structure on the same branches as the male flowers.
A wind pollinated plant, the pollen from the catkins blows to reach the female flowers. If successfully pollinated and fertilized the female flower will grow to become 1- 4 nuts C. avellana or 1–6 nuts C.maxima .
Growing Range — Corylus avellana is native to western Asia, north Africa and most of Europe, from British Isles eastwards to Russia and the Caucasus, and from central Scandinavia southwards to Turkey. Corylus avellana is native to the Balkans and Asia Minor but is widely naturalized elsewhere.
Both species are pioneer plants found in a range of habitats. As a component of ancient forests they prefer moist lowland soil and are often found growing in the shade of deciduous trees, especially oak. They can be found in hedges, meadows and pastures, on the banks of streams, waste places, abandoned plantings, the edges of woods, on steep slopes and by paths and roadsides. Hazel grows naturally up to altitudes of 700 m
Hazelnut-producing regions of the world are all close to large bodies of water, which moderate the climate. About 70% of the world’s hazelnut production comes from the black sea region of Northern Turkiye ( I have a post about hazelnut orchards of this region here) . Italy produces about 20% of world production. Spain, France, Georgia, Azerbaijan, and the United States produce most of the rest.
Hardiness USDA — Corylus avellana — Zone 4–8
Corylus maxima — Zone 5–8
Ecology — Hazel flowers are an important source of pollen for bees and other pollinators. The pollen-bearing catkins can be available to pollinators from as early as late January — late March. Hazel leaves are used as food plants by the larvae of various species of Lepidoptera. The nuts are used by dormice to fatten up for hibernation and in spring the leaves are a good source of food for caterpillars, which dormice also eat. Hazel nuts are also eaten by woodpeckers, nuthatches, tits, wood pigeons, jays and a number of small mammals.
Where to Plant
Climatic limitations — Both species crop best in areas with cool, moist summers and mild cool winters or in maritime climates. Areas with high summer temperatures are not ideal although good cultivar selection can improve results. Areas with extreme winter cold can also be problematic. The shoots of the plants are hardy to -29 C (-20 F) although winter temperatures below -10 C (-13 F) during the flowering period may damage the male flowers reducing the likelihood of fruit set that year.
The plants will not grow well in tropical or sub tropical climates and require a winter chilling period of 800–1200 hrs below 7 C (45 F) which is similar to apples.
Soil — Hazel tolerates a wide variety of soils from calcareous to acid, loam to clay and prefers soil that’s well drained and fairly low in nutrients; overly rich soil gives plenty of leaf growth at the expense of flowers and nuts. Hazels will not grow well in water logged and peaty soils. Shallow soils will restrict the growth and height of hazel.
Location — If growing for nut production in cold climates you should avoid planting in frost pockets, and in hot climates avoid windy sites. Hazelnut trees also cannot tolerate excessive heat or a long dry season. A sheltered area with a reliable source of irrigation is essential in hot climates.
Pollination — Hazels are wind pollinated. As mentioned above cold weather (-10 C and under) during the flowering time can destroy flowers and reduce fruit set. Heavy rain during the time where pollen is being released can also suppress the amount of pollen carried in the air and moist conditions destroys pollen viability.
The plants are in theory self fertile meaning the pollen from the male flowers can pollinate and fertilize the female flowers on the same plant. However, the blossoming times of the male and female flowers on the same plant do not always coincide and for this reason it is recommended to plant 2 or more different cultivars to increase the likelihood of pollination occurring. Wild growing hazel nearby will serve as good pollinating agents for most cultivars and there are many cultivars that work well together to ensure fuller cropping. There are some cultivars that absolutely require pollinating partners so research your cultivars well A good rule of thumb for how many pollinator plants you need to support you main cropping cultivar is 1 to 18. On sites where wet weather is common during the flowering period this can be increased. The pollinating partner should be a maximum of 45 m away and upwind from the main cropping plants.
Pollen is released from the male flowers in bursts across a 4- 6 week period in January — March. Interestingly, the pollen germinates as soon as it reaches a receptive flower but the fertilization process does not take place for another 4–5 months in June. Once fertilized the female flowers develop into nuts very rapidly with 90% growth occurring within 4–6 weeks.
Fertility, Irrigation and Care
Fertility — On good soils hazel will not need fertilizers. On poor soils, planting out with 30 L of compost (applied to the surface) and mulching well with straw and repeating this each spring for 4- 5 years will provide a good boost to growth. Planting nitrogen fixing companions can also be very effective. I have seen very healthy orchards growing in Ordu, Turkiye where the owners use the bracts left over from the hazelnut harvest to mulch the trees, as you can see in the below photo.
Irrigation — In cooler climates such as the UK irrigation is not necessary. In warmer climes with hot summers and long periods without rain, applying 30 L of water per tree every 3–4 weeks without rain and mulching well is very effective.
Weeding — Mulching plants with a 10 -20 cm deep mulch each spring and pulling weeds that start to grow through in the summer is good practice especially when the plants are young.
Pruning — When planting out single stemmed whips it’s good practice to prune the top down to 45 cm to encourage lower branching (a practice known as formative pruning). Hazel plants often sucker (send up many shoots from the base of the plant. Suckering growth should be removed to keep the stems clear and the crown less congested. Beyond formative pruning and removing suckers we don’t prune our Hazels but there is a tradition, as with most fruit trees, to prune in order to achieve an open centered goblet shaped bush.
If you are going to prune than it’s important to know that female flowers (that will form the nuts) are produced from buds on growth from the previous seasons growth. For optimal nut production you should aim to have plenty of previous years stems at least 15–25 cm long.
I read an interesting comment regarding a traditional pruning method used to increase nut production called ‘brutting’. This involves prompting more of the trees’ energy to go into flower bud production, by snapping, but not breaking off, the tips of the new year shoots’ six or seven leaf groups from the join with the trunk or branch, at the end of the growing season. I’ll be trying this on a few of our plants this year.
Harvesting — The nuts are fully ripe when the husks begin to yellow and can be picked by hand. Nuts will naturally drop over a 4–6 week period. It’s important to not pick before they are ripe as they will shrivel and do not keep well.
Propagation — We have grown hundreds of hazels from locally gathered seed and this is a very easy and reliable method to propagate these plants. Most of our seedling stock we use for coppice plants and hedging plants. For nut production we use cultivars as they generally fruit within the 3rd and 4th year after planting and you know what kind of nut you will end up with.
Seedlings can take up to 6 or 7 years to produce nuts and you never know what they will be like. Saying that, we have some great nut producing seedlings that we propagated from local plants. They appear to be more resistant to the winter cold and have been providing a reliable crop each year even after bitter cold late winters.
Another great way to propagate hazel, including cultivars that are grown on their own roots, is by stooling and layering. Stooling involves heaping soil at the base of the plant, leaving it for 12 months and then dividing the rooted stems. Layering is burying the stems in the soil for 12 months and cutting them off the main plant once the stem has rooted
Hazels that are grafted onto their own roots will send up suckers. The suckers can be dug out in the winter and planted on. The suckers can be a nuisance and will need cutting back to promote better production. Corylus colurna — Turkish hazel is often used as a rootstock as these are non-suckering and have a deeper rooting habit. Cultivars on Corylus colurna rootstocks are often very vigorous.
Potential Problems
Excessive Heat: Hazelnut trees cannot tolerate excessive heat or a long dry season. They are especially sensitive to drying in windy conditions.
Cold injury: Although a very hardy plant, when growing for nut production the trees are vulnerable during the flowering period in early — late winter. Temperatures below -10 C (-13 F) during the flowering period will damage the male flowers and destroy the pollen reducing the likelihood of fruit set that year. Because not all catkins elongate at the same time, crop damage usually is minimal if there is only a brief cold spell.
Insect/Pest: Grey squirrels are major pest of hazels. Nut weevils — Balaninus nucum can destroy the maturing nuts. Beetles lay eggs in the immature nuts. The eggs hatch into maggots that eat the maturing nut and bore out of the shell to pupate in the soil where they overwinter before hatching, mating and laying more eggs in the next crop. Clearing up the fallen nuts is good way to control this pest. Running chicken under the hazels in September can also disturb the pupae in the soil
Disease: In the US this species is affected by Eastern Filbert Blight (EFB), which is caused by the fungus Anisogramma anomola and is fatal to trees. However EFB can be controlled by a variety of management strategies and does not present a major threat to the species as a whole.
Bacterial Blight — Xanthomonas campestris pv. corylina causes leaf spotting, dieback of branches and in worst cases death. Trees under stress are most susceptible.
Suckering — Hazels can sucker profusely and the suckers need to be cut back to allow an open crown and avoid congestion. There are cultivars that do not sucker, generally those grown on the Corylus colurna root stocks.
Allergies: The pollen of hazel species are often the cause for allergies in late winter or early spring,
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Hazel Uses
Beyond the nutritious delicious nuts hazels can be used for a variety of purposes.
Wood — Hazel is almost as well known for coppicing as it is for its nuts. The poles from coppice (known as ‘wands’) are long and flexible and have traditionally been used for wattle fencing, thatching spars, walking sticks, fishing rods, basketry, pea and bean sticks and firewood. The wood is soft and easy to split but not very durable (See Hazel Coppice below).
Oil — The nut oil is used as edible oil and contains 65% of a non-drying oil that can be used in paints, cosmetics etc.
Animal Fodder — The twigs can be used to feed rabbits and goats all year around and the leaves are very palatable to cattle.
Leaves — Leaves contain on average 2.2% N. 0.7% K and 0.12% P and when applied as mulch make a great fertilizer. The plant has potential to be grown as chop and drop component in a polyculture system.
Hedging — Hazel makes a great hedge taking well to trimming and providing a dense screen. Nut production is not as high as when grown as free standing plants but some nuts can be harvested from the hedge. The plants are also tolerant of wind and a 2 or 3 row windbreak can be set up where alternate rows are coppiced on a 7 year cycle.
Bee Fodder — Hazel is an excellent source of early forage for bees providing a source of pollen from February through to March. We include hazel in our Early Polleniser Polyculture, a polyculture dedicated to providing an early source of pollen/nectar to a wide diversity of pollinating insects.
Medicinal uses — The leaves are used in allopathy: their effect is to stimulate circulation and bile production, and they are used for liver and gall disorders. Hazelnuts are rich in protein, monounsaturated fat, vitamin E, manganese, and numerous other essential nutrients.
Other uses — The finely ground seeds are used as an ingredient of face masks in cosmetics.
Hazelnut Yields
Hazelnut trees can produce a few nuts when they are 2 or 3 years old, but they are not considered commercially productive until 4 years of age and reach peak production from years 10–15. Mature orchards can produce 1 -3 metric tons per ha. An orchard can remain productive for about 40–50 years if managed well and kept free of disease.
Hazel Coppice
Hazel coppice has been practiced extensively in the past and still provides an excellent source of valuable wood especially if you are adding value with wood crafting.
Contrary to what you may expect, coppicing the hazel can extend the life of the plant considerably with some well managed coppices being centuries old.
Hazel can be grown on various coppice cycles for a supply of poles (‘Wands’) that are used for a variety of purposes as listed above. A 7–10 year rotation is often practiced and is planted out at a rate of 1500–2000 plants per ha (spacing is 2.2–2.6 m between plants).
In the 7th — 10th year the shoots should be 4–5m long and can be cut at any point during the year apart from August but is usually carried out in the winter. If you cut the coppice in the summer, leaves from the wood make an excellent cattle feed or mulch. Regrowth will quickly reestablish and is vulnerable to browsing from wild and domestic animals. After the first few coppice cycles, regrowth will be fast but after 15 years it will decline. If a hazel coppice is not well managed i.e cut at regular intervals for 40+ years it will die back.
How much wood can be harvested? — A site with 1500 plants per ha can yield 20 tonnes of dry wood or 40 m3 of wood per ha per cycle.
Hazel coppices are often combined with standard trees to make a two storey forest. Sweet Chestnut is a classic combination in the South of England. Oak is also very commonly grown with hazel at a rate of 30–100 standard trees per Ha. Too many standard trees will shade out the hazel.
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Hazel Polycultures
Hazels are excellent plants for use in polycultures. They are tolerant of shade so suitable in the under story, are not very nutrient demanding or competitive and are relatively compact and easy to manage. They tolerate pruning very well and can be used for chop and drop plants grown between fruit trees or in hedgerows. If nut production is sought after they should be given a prime position but can still accommodate a range of productive and useful plants around them.
We have used hazel in various polycultures including living hedges, main crop contour plantings and habitat polycultures.
Here’s an example of a design with hazel planted in a polyculture hedge designed for Permaculture Orchard - Orehite Ranch - Veslec
We’ll be planting out Hazel in our new trial garden — Ataraxia, where we’ll try growing it along with asparagus, currants, wild garlic and various bulbs in 1.5 m wide beds.
Here’s a short list of ground cover and bulbous plants that we observe growing well with hazel.
Scilla bifolia — Alpine Squill
Trifolium repens — White Clover
Corydalis bulbosa — Spring Fumewort
Agroforestry Potential Of Hazels
There is great potential for hazels in agroforestry systems. Traditionally, in Europe, hazels were grown in a silvopasture system with sheep grazing the pasture beneath the trees, this has an added benefit of controlling suckering growth. Hazel has also been grown with vines and in Kentish orchards gooseberries and currants were traditionally inter planted with young hazel.
I’ve included hazel in a few agroforestry designs the most recent being a 30 ha pastured poultry system where we’re using hazel amongst mulberry planted on contour.
Being shade tolerant the trees are good candidates for use in an under storey. In deep shade the plants will not produce a significant yield of nuts but they can be used for coppicing or mulch production. In partial shade they can still produce good yields.
Hazelnut cultivars — Hardy and Resistant to Major Pests and Diseases
There are hundreds of hazel cultivars throughout the world, not to mention the hybrids, American and Chinese species or the Trazels, Filazels and Hazelberts (perhaps a topic for another post).
Most cultivars belong to Corylus maxima but there are many Corylus avellana and many grafted onto Corylus colurna rootstock. When selecting cultivars for your garden there a few things to consider.
flowering times — to avoid cold damage in the winter choose a late flowering cultivar
suckering behaviour — to avoid pruning work or perhaps if growing for mulch or biomass this could be desirable
size and vigor — to select the right size plant for your garden
pollinator partners — to facilitate larger and more reliable yields
Below you can find profiles of some excellent cultivars that we have on offer at our Bionursery.
We are currently offering cultivars at €7 per tree with 15% discount for orders over 100 trees.
Corylus avellana — ‘Ata Baba’
Fruit — Round medium size fruits of 1.4 g grouped in clusters of 3 or 4 . Ripen in mid August
Pollination — Self fertile
Hardiness — Full hardy withstanding temperatures as low as -34 C
Disease Resistance — Corylus colurna root stock which has a high resistance to the main European pests attacking hazelnut crop
Form — Bush variety, very vigorous multistemmed and flowering early towards the end on December
Corylus avellana — ‘Ran Trapezundski’
Fruit — Great tasting large oval fruits with thin shells that ripen at the end of July
Pollination — Not Self fertile — Pollinated by Rimski, Bademoviden and Atta Baba
Hardiness — Full hardy withstanding temperatures as low as -34 C
Disease Resistance — Corylus colurna root stock which has a high resistance to the main European pests attacking hazelnut crop
Form — Bush, medium vigor, multi stemmed, fruits abundantly.
Corylus avellana — ‘Rimski’
Fruit — Large rounded nuts about 2.7g. Thin shell. 67% fat content. The fruits ripen in mid August
Pollination — Not Self fertile — Pollinated by Bademoviden and Ran Trapezundski
Hardiness — Full hardy withstanding temperatures as low as -34 C
Disease Resistance — Corylus colurna root stock which has a high resistance to the main European pests attacking hazelnut crop
Form — Bush variety. fast growing, multi stemmed with an upright crown.
Corylus avellana — ‘Tonda Gentile’
Fruit — Excellent flavour, med — large round nuts of 2.5g with a thin shell
Pollination — Not Self fertile — Pollinated by Rimski, Bademoviden and Ata Baba
Hardiness — Full hardy withstanding temperatures as low as -34 C
Disease Resistance — Corylus colurna root stock which has a high resistance to the main European pests attacking hazelnut crop
Form — Moderate growth rates and can be grown as single stemmed trees
Corylus avellana — ‘Cosford’
Fruit — The nuts have hard shells.100 g of fresh nuts contains 13 g protein, 61 g fat, 13,7 g carbohydrates and 3.5 g fiber. They mature in late September.
Pollination — Self fertile, a good pollinator for many other Hazels, a good choice if you are starting your own nut orchard.
Hardiness — Full hardy withstanding temperatures as low as -34 C
Disease Resistance — Generally disease free
Form — Bush variety. fast growing, multi stemmed with an upright crown.
To order some hazel cultivars for delivery this winter contact us at balkanecologyproject@gmail.com
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I read that putting the nuts in the freezer for a few minutes changes the structure of the shell so it breaks easier. Or in the oven at 150 Celsius or something like that. Gonna try that in combination with your hammer method.
Is there a tool for opening hazelnuts, apart from the common one where you have to open one after another?