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| . Hazel - Corylus Avellana
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Natural History. Hazel is a large shrub, which colonised these islands after the end of the last glaciation (circa 12,000 BP), but before the final disappearance of the land-bridge which linked them to the continent (circa 8,000 BP). The exact mechanism of colonisation is unclear as geological evidence from the early Holocene period (circa 9,500 BP) suggests that hazel pollen was present in huge amounts and implies that hazel was present for around 1,000 years before the spread of other trees. The increase in the pollen was sudden: without the usual "tail" of increasing amounts over time. Hazel, having a relatively large heavy nut, is not a very good pioneer species compared to species with light, windborne seeds e.g. Ash (Fraxinus Excelsior) or Birch (Betula spp.). So how it managed to get off it's starting blocks so quickly is something of a mystery to science. With good light levels, a sheltered position and no browsing, hazel will naturally grow into a multi-stemmed shrub; with the largest stems reaching up to 30' in height. There will usually be a thick, contorted central trunk with an abundance of shoots growing from around the base. New shoots will be produced each year: giving a range of stems, of differing heights and thickness, to each shrub. As the leaf canopy closes and light levels are reduced, the new shoots that are produced in any given year will die off. However, should a gap in the canopy occur, e.g. due to one of the larger stems collapsing, these shoots will be able to grow on. Male catkins are formed in late summer/early autumn but do not mature until January/February the following year. The tiny, dark-red female flowers appear at the same time that the male catkins are opening and lengthening. They are very inconspicuous and can be found growing from some of the tightly folded leaf buds. The hazelnut forms from the ovary of the female flower. The fertilisation process must be done before the leaves unfurl as hazel, in common with most other forest species, is wind-pollinated. Milder winters, and consequent earlier leaf-burst, will reduce the amount of nuts produced the following summer. A colder winter, with later leaf-burst allowing for a longer pollination period, will be followed by a larger crop: a "mast" year. This variation in the annual amount of nuts produced acts as a break on the population of the small mammals which feed on them: thus ensuring that enough hazelnuts actually to grow into young plants. Well, so much for that theory. Although 2006 conformed to the colder winter pattern, 2007 was completely different: a very mild spring, resulting in early leaf-burst. The hazelnut harvest was, however, just as abundant as in 2006. The difference has been in the quality of the crop: with a great many empty shells and rotting nuts. Hazel seems to attract more wildlife than any other tree in our wood. Walk past an oak, an ash or a birch tree and - nothing. Yet a hazel is a veritable hive of activity. Ladybirds constantly patrol the broad grren leaves for aphids, etc. They also like to rest inside the ragged outer husks of the hazelnuts in autumn and can often be found sheltering at the sheltered bases of the hazel during the winter. A host of other insects, flies, butterflies and, even, on occasion, damsel- and dragonflies, are attracted to this plant either for food, shelter or prey.
Propagation. Growing hazelnuts in pots It is not possible to do the normal "float" test for hazelnuts: they all seem to float whether or not they are viable. I now plant several nuts in a large pot. After a year I transfer all that have grown into individual pots: to grow on for a second year. In the autumn of the second year I weedkill the selected planting areas, wait for the weedkiller to take effect, plant the hazel and protect them with old Tubex shelters. The young plants need to be protected from grass and weed competition by applying weedkiller around the plant until they are established. Direct sowing hazelnuts Hazelnuts can also be planted directly into the ground. The main drawback with this approach is that all of the nuts are likely to be dug up and eaten by mice: which seem to be attracted by the smell of the hazelnuts. I find it best to wait until the spring and then; Hazel grown in this way sometimes take a couple of years to emerge so don't give up too early. It will still be necessary to spray weedkiller on an area 18" around the plants until they have established. Cuttings For all those people searching on this topic: give up. I have had no success to-date with hardwood cuttings. However, this winter I intend to experiment with cuttings using a Willow Rooting Substance (WRS). WRS is made by stripping bark from 1 year-old willow stems and then boiling it in water for 10 minutes. The water is then left to stand for a couple of days. The hazel cuttings can then be dipped into the WRS before being inserted into the ground or pot. Stooling This procedure involves producing rooted cuttings from a well-established Hazel bush. I have found that for best results you need to identify a plant that tends to produce lots of new stems, and then keep it in an open, sunny environment. In late Autumn, when all the leaves have fallen, all of the existing stems should be removed. Monitor the plant during the following summer and when the new shoots are around 9" tall start to mound up earth around them, keeping the leaves clear of soil. As the new stems grow then keep topping up the mound. The mound must be kept damp. Stop the mound from sliding away by cutting the bottom from an old washing-up bowl and placing it around the base of the plant. I find that it is best to use compost and not ordinary garden soil. In the Autumn/Winter of the second year the new stems should be ready for cutting and transplanting to their new sites and the process can begin again. Layering This is a very good way of establishing new stools within an established area. When the neighbouring trees are in full leaf it may not be easy to access the new plants to maintain them. Actually, I usually forget that they are there. I find it best to use healthy, 2-year-old stems. I try to use one that is naturally low-lying; otherwise I have to cut through the stem until it lies easily on the ground. I cut out a narrow trench with a trowel and lie the stem in it. I often use several stems from a single stool. I make pegs from the forks in pruned oak branches to hold the stem in place: making sure that the whole length is in contact with the earth. I find that, unlike hazel, oak pegs don't split when thay are hammered in. I then cover over the layered stem with earth and carefully tread it down The literature recommends that the end 12" is partly cut through, bent upwards and loosely tied to a cane. I do do this: it doesn't seem to do any harm, but the end of the stem rarely seems to root. Roots grow from any dormant buds along the length of the stem. So you will find that you have not one but, probably, half-a-dozen new plants from your layered stem. When I am next coppicing the section, I simply cut the old stem where appropriate and the new plants will then support themselves. Remember to place the layered stems along the line of your rows: you don't want hazel growing where you should be mowing.
Cultivation. Hazel does well on most soils with a pH of between 4.5 and 7.5; growing best on well-drained, reasonably fertile, moderately acid to basic soils; it will thrive on both loam and chalk. However if coppiced for craft use, Hazel is best grown in heavy, clay soils and along waterways. Cultivation in these conditions will result in hazel rods that split easily for use in thatching and hurdle making. Hazel grown on lighter, free-draining soils may be too brittle for these trades.
Planting & Aftercare. Hazel must be protected from browsing mammals. Single-stemmed transplants (whips) can be protected by tree guards initially. But new shoots will soon start to emerge from around the outside of the guard; these will be susceptible both to browsing and to herbicide. I have found that adequate rabbit fencing is essential for acceptable regrowth. I found it best to buy 2-year-old whips between 60-90 cms in height. These are grown for a year, then the taproot is undercut and the tree tranplanted to a new bed (1U1 in the jargon). Undercutting in this way stimulates a bushy root system and results in quicker growth of suckers from the roots. I bought them in bundles of 25 from Forest Nurseries. The quality varied enormously, so it's best to find a good supplier and stick to them. I often found tiny seedlings lodged within the bundles. If potted up for a year, they invariably survived and grew into healthy, and free, plants. Also, many plants were forked at the base. Where both parts of the fork had even the tiniest whisp of root, they could easily be pulled apart; and both stems potted-up and grown on for planting in the following year. Where whips are planted, the original stem should be removed (by pruning as close to the ground as possible with loppers or secateurs) as soon as the bush has established successfully. A good rule of thumb is to wait until separate new stems have emerged around the original one. The tree guard should be removed as soon as possible to prevent field voles from over-wintering in them and "ring-barking" the stems. Cleavers (Galium Aparine) This is a weed of arable cultivation. A single plant can produce 2,000 seeds, each capable of lying dormant in the soil for up to 3 years. Implementing a coppice regime on a farmland site produces the ideal conditions of damp shade for this plant. It likes to scramble up other plants and smother them; and the plant that offers the best opportunites for this is newly coppiced hazel. Cleavers grows from around late April/early May. It is best to start treating it as early as possible: once it has set seed then the battle is lost for another year. It is almost impossible be pulled out by hand as the stems are very brittle and snap off near the ground: allowing the roots to regrow Either Glyphosate or a selective broadleaf weedkiller (Relay) can be used to control Cleavers within the wood. To minimise spray drift it is best to only spray on calm days. Also, I used to pull the strands of Cleavers from the plant and lie them on the ground where I can spray them without getting weedkiller onto the leaves of the tree/shrub. However, despite all my best efforts I could not precent cleavers from becoming well-established over large areas of the wood. The good news is that established hazel seems perfectly able to cope with cleavers; so now I leave it alone and concentrate on the really important weeds. Ivy (Hedera helix) The consensus of expert opinion seems to be that Ivy does not adversely affect hazel coppice regrowth. However I haven't yet spoken to anyone else who actually coppices hazel for their opinion so I don't intend to take any chances. During coppicing operations I pull up all of the Ivy strands that are growing over the hazel stool and remove them for burning. Then I spray any Ivy on the woodland floor that is away from the hazel with Glyphosate. Ivy has a waxy covering (cuticle) on its leaf surface which reduces the effect of weedkiller. To overcome this I add washing-up liquid to the solution in order to make it better adhere to the leaf surface. See the Fieldlayer page for more information on problems with weeds, management of light-levels, etc.
Formative Pruning.
This is not strictly necessary for Hazel as the main object is to cut the stems down to ground level or "coppice" them. However, as this is a new planting and does not yet have an optimum stocking density, I have found it advantageous to retain the outer stems and to apply the standard formative pruning techniques to our hazel. In order to be able to grow good quality hedgelaying binders, we want to reduce the amount of vigour going into large side shoots and to prevent crossing branches and multiple leaders. This lets the plant put on the height we require for hedgelaying binders whilst keeping the butt diameter to below 1". Retaining the outer stems reduces the amount of light around the sides of the new stems and causes them to head straight upwards towards the main light source. After the first year's growth I visit each hazel in turn and perform the followiing routine. For each major inner rod: reduce to the single best leading shoot; remove any side branches with a diameter > 50% of the main stem; reduce any crossing side branches - to reduce bark damage from rubbing; remove any dead or damaged branches.
For each outer rod: 1. remove any inward growing side branches.
Timber Properties.
The best bit about Hazel wood is the bark. Normally a rich, dark brown with flecks of yellow. Hazel is a fairly brittle wood especially if grown in light free-draining soils. The stems being prone to snapping at the base in windy conditions. Hazel really needs to be grown in as sheltered a spot as possible. Constant twisting around in the wind seems to cause the grain of the wood to become distorted and more difficult to split (or cleave). Stocking density is particularly important in this respect: no more than 1.5m between each plant and leave the 2 outermost rows on each edge as a windbreak for the rest. Hazel is a "diffuse-porous" timber. It is mostly comprised of sapwood with a density of. 640 kg/m -3.
Hazelnuts. Growing Hazelnuts are a subject close to my stomach. They are also the basis of a minor foodchain
that I have noticed over the years. Virtually all of the hazel bushes that we have planted appear to have at least one, sometimes two or even three, mouse nests around them. After the hazel have regrown for several years, their canopy is quite dense and offers both shelter for these nests from the weather and obscurity from their natural predators: just about everything.
After about 5 years' growth, the hazel also start to produce large quantities of nuts (although the amount does vary from year to year). Resulting, every September, in a tense stand-off between
me and the mouse population as to who gets to the nut-crop first.
Every winter I coppice several hundred of the hazel. With the result that their nice cosy, secretive
nests are suddenly turned into a barren wilderness; completely obvious to any passing Owl, Kestrel, Fox, etc. The resulting carnage clears out a large number of nests; which bees, both bumble and honey, can then colonise the following spring. We intended to plant only native hazel (Corylus avallana), but the various forest nurseries that we bought from managed to supply us with C maxima and C. maxima purpurea as well. Furthermore, although hazel is a native species, it is likely that many of our hazel were foreign imports. The good part about all this is that a lot of trees are producing the (large) cob nuts and not the (tiny) hazelnuts. Picking It would seem to be an iron rule of biology that all of the best nuts are at the very top of the tree. Unfortunately, every year I forget this and leave all of my cunningly contrived crook sticks behind. Thus affording me the endless pleasure of crashing around in hazel bushes in a forlorn attempt to reach the particularly inviting ones around 15 or so feet above me.
Getting at those on the lower branches has its problems too: as they are inevitably entwined in
stinging nettles. The whole tree being tightly encircled by dead and decaying thistles; whose dried up leaves still pack a punch when they fall down the inside of one's Wellington boot. I am still eating last years crop. They keep perfectly well for at least a year in a cool dark place. Archaeologists seem to think that stone-age people needed to roast them in order to preserve them, but I disagree. I have tried heating them in an oven and the only advantage that I detect is that it makes the, shells softer and, therefore, easier to open without the help of any Mesolithic nutcrackers. Problems Nut Weevil A small proportion of our hazelnuts are subject to the attention of a weevil. The nut weevil, like all weevils, is a beetle with a long snout or proboscis which has positively elephantine proportions in the female. She uses it to drill a hole into the young nut as soon as it is set and the shell is still soft. A single egg is laid in the developing kernel, and the hole heals over so there is no sign of infestation. The egg hatches into a grub which feasts on the kernel until the nut falls. The now empty nut has a hole where the young weevil emerged. Hazelnut Weevil: Curculio nucum Parthenocarpy This is when a fruit is formed wthout fertilisation by pollen and has no seed. This is fine for grapes but a hazelnut with no nut is just annoying. Many of our bushes seem to exhibit this in one of their stems, whilst one of our filberts (Corylus maxima) is completely and consistently parthenocarpic. A symptom of this problem is that the nuts remain on the branches all winter.
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