Irish Nut Growers Association
promoting nut growing in Ireland
For good production, it is essential to grow named cultivars (varieties) that are known to perform well in climates similar to Ireland.
Nut trees grown for nut production need to be propagted vegetatively, either by stooling, layering, grafting or from cutting. Such trees will come into nut production early in life, usually within 4 to 8 years (depending on the variety)and will produce identical nuts to the parent tree.
Conversely, nut trees grown from seed (nut) may not come true but may revert towards the wild form of the tree. Also seed-grown trees generally take much longer to come into nut production (typically 12-20 years in the case of walnuts or sweet chestnuts) meaning a long wait to discover whether the nuts are of a good quality.
There are literally hundreds of different varieties of each of the nut species. However, the varieties most suitable for Ireland are generally those that are grown in climates relatively similar to ours.
The selection listed below is by no means comprehensive, but includes most of the varieties that show potential for nut production in Ireland.
Nut species that have only marginal potential in Ireland are also listed, and the reasons for their limited potential are provided.
Different species of nut have different soil and site requirements. However, all do better on warm sheltered sites, and in well-drained soil. None like extreme acidity, or waterlogging, or sites that are prone to late spring frosts.
Monkey Puzzle (Araucaria araucana )
The Monkey Puzzle is native to the southern Andean region of Chile and Argentina. It grows in upland regions where the rainfall is similar to the west coast of Ireland. A very long lived tree, it is known to produce viable nuts in Ireland. However, nut production only begins after 25-40 years. As a long term nut option for future generations, the Monkey Puzzle is worthy of consideration. Male and female flowers occur on different trees. There are no known cultivars.
Pecan (Carya illinoensis)
The Pecan tree is native to the United States. The Northern Pecans are cultivated forms that have produced good crops as far north as the northern United States and southern Canada. However, the climate in this part of North America is very different to Ireland. Southern Canada has a summer climate similar to Central France, providing ideal conditions for the nuts to develop and ripen. While in a favourable location, Northern Pecans may occasionally produce crops in Ireland, they should be regarded as an outside bet.
Shagbark Hickory (Carya ovata)
The Hickory tree is native to the United States and parts of southern Canada. Of the 8 or 9 recognised different species, the Shagbark hickory produces the tastiest nuts. It is much better adapted to short growing seasons than the pecan and more likely to produce a crop in Irish conditions. There are a large number of different cultivars. However no concensus exists as to which cultivars would be most suited to the Irish climate. Susceptibility to spring frost is likely to be an issue. At the present time no trials have been carried out in Ireland.
Hican (C. illinoensis x C.ovata)
The Hican is a naturally occuring hyrid between the pecan and hickory, combining the taste of the former with the hardy characteristics of the later. There are a number of different cultivars. At the present time no trials have been carried out in Ireland.
Sweet Chestnut (Castanea sativa and Castanea sativa x C.crenata)
The Sweet Chestnut (Castanea sativa) is native to Southeastern Europe and Western Asia while its close cousin Castanea crenata hails from Japan and China. Crosses between the two (Castanea sativa x C.crenata) have greater vigour and greater disease resistance than C. sativa, and play an important part in modern chestnut production.
Chestnuts require deep, fertile, well-drained soils. They will not grow well on limestone but will cope with greater acidity than most other nuts. Ideal pH is 5.0-6.0. The best results will be achieved on warm sheltered sites. However, chestnuts can tolerate some wind and may cope with high rainfall areas better than the walnut.
* indicates C.sativa x C.crenata hybrid
Selection of varieties
Trials carried out by the Agroforestry Research Trust in the UK indicate that of the varieties listed above, the hybrid chestnuts give the highest yields. Nut quality is similar to the non-hybrids. The hybrid varieties are generally more disease resistant. However, the non-hyrid varieties leaf later and consequently are less vulnerable to spring frosts.
Of the varietes listed above, the best pollen producers are Belle Epine, Marron de Goujounac and Vignois, followed by Marigoule, Bournette, Marsol, Rousse de Nay and Verdale. The varieties Marlhac and Marron Comballe produce little or no fertile pollen. Most of the pollen-producing varieties are partially self-fertle. However, it is recommended that chestnut orchards include at least two different pollen-producing varieties.
Cobnut/Filbert (Corylus avellana and Corylus maxima and hybrids
The cobnut is a cultivated form of the Common Hazelnut while the filbert is the Balkan version. The cultivated forms are very similar and there is much confusion about which varieties have which ancestors. In order to avoid confusion, both types of nuts are often referred to as cobnuts (as we do here). There are hundreds of known different varieties. Generally speaking, the ones that do best in Ireland come from nearby European countries (UK, France and Germany), with a few varieties from Southern European countries and from North America.
Cobnuts are grown commercially in parts of the UK, Germany, France and the Netherlands. They can tolerate a wide variety of soils but require a moist fertile soil (not waterlogged) and shelter from wind for the best results. In the last five years, several large cobnut orchards have been planted in Ireland.
Selection of Varieties
In trials carried out by the Agroforestry Research Trust in the UK, the varieties Hall's Giant, Nottingham, White Filbert and Webb's Prize showed the biggest yields, followed by Cosford and Corabel. However, these results do not reflect long term yields and should be treated with a certain amont of caution.
Cobnuts are not self-fetile so more than one variety should be planted. Male flowering (catkins) generally commences early in winter and continues till March.The catkins elongate and swell at the time of pollen release, which begins in early January. The tiny red female flowers (which are found on the tips of buds) are first seen in January and continue till March (occasionally April).
Ginkgo (Ginkgo biloba)
The Ginkgo tree is better known for its ancient lineage and for its spectacular foliage but in China, Korea and Japan is also cultivated for its edible nuts. Nut producting capability in Ireland is unknown but appears probable. The trees are are long lived and grow very large. Also the trees are dioecious, meaning that male and female flowers occur on separate trees. Seed-grown ginkgo are very slow to reach nut bearing age. However, a number of cultivars exist, propagated by grafting. Female cultivars will reach nut bearing capability within about ten years.
Heartnuts (Juglans ailantifolia var cordiformis)
Originating in Japan, the Heartnut is a close cousin of the walnut. It grows relatively well in maritime climates and may be more disease resistant than the walnut. In terms of nut production, it appears to have great potential in Ireland. Modern varieties have produced nuts as far north as Northern Michegan and Southern Canada. Heartnuts require deep fertile and well-drained soils with a relatively high pH (above 6.0). Site requirments are similar to walnuts.
With the exception of Kalmar, which is from Sweden, the other varieties listed above are from North America.
Selection of Varieties
Given the pioneering nature of heartnut cultivation in Europe, no comparitive data exists on yield or other indicators of performance. Equally, the situation regarding pollination is somewhat confused. The intending heartnut grower is advised to plant a few different varieties within relatively close proximity, in order to maximise pollination possibilities.
Butternut (Juglans cinnerea)
The Butternut is native to North America. It requires long warm summers to do well. It is not recommended for growing in Ireland for nut production, though may occasionally produce nuts in some favourable locations. The tree itself is quite hardy. A two hundred year old tree can be seen growing at Ulvik, in the Hardanger region of Norway. The closely-related Buartnut (see below) is more likely to produce nuts. Soil and site requirements are similar to walnuts.
Common Walnut (Juglans regia)
The most common of the Juglans family, the Common Walnut originates from South-East Europe and Western Asia. It has been grown commerically as far north as the UK, Holland and Poland, and as far west as Western France. Trees have produced nuts as far north as Northern Scotland and Southern Norway.
In an Irish context, the most promising varieties are mainly those that have done well in martime climates in other European countries. Walnuts require deep fertile and well-drained soils with a relatively high pH (above 6.0). They tolerate limestone but must have shelter from wind. High rainfall areas are not suitable. However, walnuts have the potential to produce good crops most years in many parts of Ireland.
Corne du Perigord
Non French varieties
Selection of varieties
The French varieties listed above have all performed well in the trials carried out by the Agrofrestry Research Trust in the UK. Fernor and Fernette are lateral bearers, with the potential to come into production earlier and produce bigger crops. The non-French varieties tend to flower earlier and are vulnerable to spring frosts.
For pollination purposes, walnuts are generally grouped into early flowering and late flowering varieties, though some varieties (for example Ronde de Montignac) have a long flowering period and can be considered to be both early and late . Early flowering varieties may be susceptible to spring frosts. While some varieties are partially self-fertile, pollination is always more successful when two or more different varieties are planted together.
Black Walnut (Juglans nigra)
The Black Walnut is native to North America. Although very cold hardy, it requires long warm summers for good nut production. It is not recommended for growing in Ireland for nut production, though will grow into an attractive tree. Although the Black Walnut is only rarely planted in Ireland, it is becoming popular in the UK, both for timber and amenity value. Soil requirements are similar to the Common Walnut.
Buartnut (Juglans x bixbyi)
The buartnut is a cross between the Heartnut and the Butternut. The hardier varieties are very similar to the Heartnut. Soil and site requirements are similar to walnuts.
The variety Mitchell, developed in southern Ontario, Canada (where summer temperatures can reach in excess of 35 Celsius) may have some potential in the warmer and drier parts of Ireland.
Pinenuts (Pinus pinea and other species)
The Mediterranean Stone Pine (Pinus pinea) is the sole source of commercial pinenuts in Europe. It grows extremely well in Ireland and produces regular crops of nuts. Nut production begins at about ten years. For best results a number of trees should be planted.
There are many other species of pine that have potential for nut production in Ireland. Among the most likely candidates are the Swiss Stone Pine (Pinus cembra), the Korean pine (Pinus koraiensis) and the Chilgoza pine (Pinus gerardiana).
Almonds (Prunus dulcis)
The almond is native to Asia and was brought to Europe in ancient times. Closely related to the peach, it requires a warm dry climate in order to do well. In damp climates it is very prone to fungal and bacterial diseases. In Ireland, the almond is only likely to succeed in very favourable locations in the sunnier and drier eastern or southeastern counties, preferably on a sheltered south-facing wall.
Cultivated varieties are normally grafted onto St Julien A (plum) rootstock. The variety Ingrid, grown successfully in southern parts of Scandinavia is the variety most likely to succeed.
Oak (Quercus ilex and other species)
Many species of oak produce edible acorns. They have been used as a staple food by indigenous peoples for thousands of years, from long before the era of agriculture. From a food perspective, acorns can be considered a very reliable crop. For Irish conditions, the best species is the Holm Oak (Quercus ilex) an evergreen tree native to the Western mediterranean and the Atlantic coast of Portugal and Spain. The holm oak grows well in Ireland and produces regular crops (typically one good year followed by a few years of much lower yields).
Another good choice is the Cork oak (Quercus suber), also native to the Mediterrean. The Cork oak is only frost hardy down to about minus ten Celsius and is not suitable for cold inland locations.