Subscribe today!

Feature imageNew nuts on trial

Sue Stickland visits the Agroforestry Research Trust in Devon to see some familiar nut trees – but also some rather surprising ones – and gets some growing tips

Nuts in the garden

Manure!

You might think that nut trees take up too much space for any but the grandest gardens. Dwarfing rootstocks like those for fruit are rarely available, and often more than one tree is needed for pollination, in order to get a good crop. However, this is not always the case. Some trees are relatively compact, or can be restricted by pruning or training, and you can often find self-fertile varieties which will crop when grown alone. And when looking at a site, don’t forget that nut trees can be as attractive as any ornamental, as well as giving you a tasty nutritious crop.

Hazelnuts
These are one of the best nuts for gardens. They can be kept small by growing them as multi-stemmed trees and selectively coppicing out the largest stems (cutting them to a few inches above the ground) and allowing new ones to grow. They will often start cropping when just two to three years old. Hazels are not self-fertile, but wild hazels in nearby woods or hedgerows will often act as pollinators. Cultivated varieties give much higher yields, so just one tree in the garden could give a worthwhile crop.

Almonds
These can be grafted onto the plum rootstock ‘St Julian A’ to give less vigorous trees, up to 5m (16ft) high, and the varieties grown for nuts have blossom as beautiful as any of the ornamental types. They can also be restricted by fan-training against a wall, like a peach or nectarine, and self-fertile varieties such as the Dutch variety ‘Robijn’ allow just a single tree to be grown.

Walnuts
These will eventually make fairly large trees but they are slow growing, and some varieties such as the East European variety ‘Rita’ are comparatively small. They can start cropping at a young age – within two to five years. Recently the French have bred varieties which bear nuts on short sideshoots or ‘spurs’ (the way most apple and pear trees bear fruit) instead of on the shoot tips, which means they can be pruned to restrict their growth without losing yield. Most varieties need pollination, but a few such as the old French variety ‘Franquette’ are partly self-fertile and would crop as a single tree.

Sweet chestnuts
These make big trees – even the more compact Japanese/European hybrids need around a 10m (33ft) spacing. They also need cross-pollination to give a good crop, although some varieties, such as early ripening ‘Marigoule’, are sometimes recommended for planting as single trees. The only way to restrict their growth would be to coppice them like hazels.


Rarely are nuts considered serious crops for British gardeners and growers – a few ornamental hazels or an old walnut or chestnut in parkland are usually all that is to be seen. However, at the Agroforestry Research Trust near Totnes in Devon, director Martin Crawford has reason to think that this could change in the future.

For the last 12 years, he has been running eight acres of nut tree trials – looking both at different varieties of more commonly grown nuts, such as hazels and walnuts, and at seemingly unlikely ones such as pecans, pine nuts and hickory nuts. Many of the trees he planted in 1996 have been cropping for long enough to give meaningful results – some of these very positive.

The lack of cultivated British nut trees can’t be blamed just on the climate. They are grown successfully in areas with similar conditions to ours – in North America, France and Eastern Europe, for example – and while other countries have been carrying out research and breeding work into new varieties, it appears that we simply haven’t been trying. Martin has been searching abroad for varieties which might grow well in the UK today, and also for ones that could have potential in the warming climate of the future.

Building on tradition

The sorts of characteristics Martin looks out for in traditionally grown nuts are cold tolerance, resistance to disease, earlier harvests and higher yields. For example, European chestnuts (the ones usually found growing ‘wild’ or in parklands) were probably originally introduced here by the Romans, and are not necessarily the best for our climate. Those that Martin has been trialling come mainly from Western France, where breeders have hybridized European and Japanese chestnuts to give varieties that are healthier, and give heavier crops of bigger nuts.

Most of Martin’s 11-year-old chestnut trees started cropping in their third year, and can now yield as much as 55lb (25kg) of nuts per tree – twice the yield of the common chestnut and as good as commercial crops in France. “All the present UK consumption of sweet chestnuts could probably be grown in this country,” he says. Different varieties have different ripening times, spread over four to five weeks, and it is important to choose early ripening varieties for areas with short seasons. According to Martin, given the right varieties, sweet chestnuts could be grown as far north as Edinburgh or southern Sweden.

French walnuts

The UK’s short growing season can also cause problems for walnuts, this time because the young foliage is susceptible to late spring frosts. In more northern areas, varieties that are late coming into leaf are the most successful, and some of the old French varieties such as ‘Mayette’ and 'Parisienne’ are notable for this characteristic. Martin has also found varieties with good resistance to the bacterial disease walnut blight, which causes black patches on the leaves and in damp conditions can spread to and damage the nuts.

Similarly, you might think that pine nuts need Mediterranean sunshine, but on the Devon trial ground, stone pines (Pinus pinea) already 5m (16ft) high are producing a harvestable crop. This is the main species grown commercially for pine nuts in Southern Europe, but in Martin’s experience, the trees also do well in mild areas of Britain. However, neither here nor in the Mediterranean do they produce high yields.

Other surprises on the site include the North American shagbark hickory with its rich yellow autumn foliage, and the large-leaved ‘heartnut’ or Japanese walnut, which is almost tropical in its exuberance.

A puzzler

What is the familiar monkey puzzle tree doing here? Apparently, its long cones contain 200-300 edible starchy seeds – ‘a bit chestnuty’ Martin describes them. However, the trees don’t start cropping until they are at least 25 years old, and eventually grow to 30m (100ft) – so not a quick crop for the garden, but a valuable inheritance.

Edible acorns

The acorns from British native oak trees are made inedible by the bitter tannins they contain. These can be leached out by roughly grinding the kernels and soaking them in water for several days, changing the water every day until it no longer turns brown. The acorn meal can then be cooked – in bread or flapjacks, for example. However, the acorns from the evergreen holm oaks (below) contain hardly any tannins, and can be ground and cooked straight from the tree, without any other processing.

War on squirrels

There is no contest for the most troublesome pest of nut crops. Grey squirrels not only take the nuts (often before they are ripe) but strip bark from the trees too. Martin has tried every type of deterrent he can find – smelly repellents, flashing gadgets hanging on the trees, even artificial hawks suspended 8m (26ft) high.

And the results? “Best summarised as deterrents don’t work!” says Martin, who watched the squirrels gallivanting underneath the hawk ‘laughing at it’. The only deterrent that he has found at all successful is a plastic blow-up snake, which makes the squirrels very wary for a week or two. The snakes need to be placed where they can be seen easily by the squirrels and moved around regularly, which makes them impractical on a large scale, but in Martin’s experience, they can be effective in a garden.

On his trial ground, lethal measures are unfortunately necessary. Martin uses cage traps covered with black plastic to catch the squirrels live – he baits the traps with whole dry maize, which the squirrrels love, and places them along the line of hedges and windbreaks. Such live traps must be visited at least once a day by law. Any other creatures caught can then be released (although Martin rarely finds any), but the squirrels must be humanely killed – it is illegal to release them elsewhere.

Agroforestry can be explained as the integration of trees within agricultural or horticultural crops to create a more diverse growing system. It encourages more use of perennial crops, especially trees and shrubs, as these have several advantages. In particular they are more resilient to extreme weather conditions than annual crops (a characteristic which may become increasingly important with climate change) and they need less labour and energy to maintain.

Forest gardens are agroforestry on a small scale, and can be created by anybody in their back gardens, using fruit and nut trees and edible leafy perennials, plus medicinal and other useful plants. The aim is for it to be as self-sustaining as possible.

The Agroforestry Research Trust (ART) is a charity conducting research into all aspects of agroforestry. As well as the nut trials, other features of its work include collections of less common fruits, experiments with nitrogen-fixing trees, and a two-acre forest garden. ART also has a nursery growing a whole range of fruit and nut trees and unusual edible plants, and sells these (and seeds) by mail order.

To see the projects, you can book on one of the limited guided tours of the site, led by Martin Crawford, or go on one of the Trust’s weekend courses. Agroforestry Research Trust, 46 Hunters Moon, Dartington, Totnes, Devon TQ9 6JT www.agroforestry.co.uk. Martin’s DVD A Forest Garden Year is available from Green Books www.greenbooks.co.uk.


For more see this month's issue, available to buy online!

How to get KG

Subscribe today

Subscriptions
Subscribing to KG will save you time and money. Copies are delivered to your door, and generally before they go on sale.

• You can subscribe or renew secure online from our own magazine shop.

• You can also contact us during office hours on: 01507 529529

• Back issues are available

Kitchen Garden
is available monthly from all good newsagents throughout the UK.

• You can also buy a single issue (current issue or pre-order the next issue) POST-FREE online.