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Author Topic: The Amazing Hazel - The Essential Guide to Everything you need to know about Haz  (Read 762 times)

Balkan Ecology Project

  • Joined Feb 2015
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.

To view this post with tables , photos and diagrams go over to our blog here - https://balkanecologyproject.blogspot.bg/2017/07/the-amazing-hazel-essential-guide-to.html



Hazel - Corylus spp,

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.


The leafy bracts that envelope the nuts are the easiest way of telling the species apart.

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 we'll look at some of my favourite hardy productive and disease resistant cultivars that we are offering from our Bionursery.

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.
   



Corylus avellana - Common Hazel



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 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 naturalised 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 Turkey. 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 flower that will go on to form nuts. However, the blossoming times of the male and female flowers 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 nuts very rapidly with 90% growth occurring within 4 - 6 weeks.             


Fertility, Irrigation and Care

Fertility - On good soils hazel will not need fertilisers. 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.

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. We don't prune our Hazels but there is a tradition, as with most fruit trees,  to pruning to achieve an open centered goblet shaped bush.  If you are growing plants that sucker, suckering growth should be removed to keep the stems clear and the crown less congested.



A classic pruning example practiced in commercial hazel orchards

If you are going to prune than it's important to know that female flower (that will form 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 method 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.



Layering and Stooling

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 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. These 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 providing non-suckering cultivars and 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.   


Nut Weevils - Balaninus nucum Photo from - https://www.flickr.com/photos/eric-dutoit/5956692789


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,

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).


Adding value to the coppice material


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.
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pgkevet

  • Joined Jul 2011
What do you know about variation/mutability? I have vast amounts of hazel in my farm hedges.. small nuts, looked from the pointy end and they are rectangular with curved walls in section. However this year i have spotted some variations. One bush with larger more triangular shaped nuts when viewed from the pointy end and 2 others with even much larger almost spherical nuts. I haven't done a proper section but a cursory look yesterday when i cracked a green one made me wonder if they are polyembryonic and whether they would breed true from seed??????. Certainy instead of being the small hedrow nuts these are commercial size in appearance.

pgkevet

  • Joined Jul 2011
I checked properly just now ..single embryo

 

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