Walnut Tree (Juglans spp.) includes a number of species that are interesting for our Swedish conditions. Genuine walnut (Juglans regia), which is also the most famous walnut usually do to the cultivation zone 2 in Sweden. The genuine walnut big advantage is that they are tasty nuts are easy to crack and the nuclei remain intact and are easy to get out of the shell.
Its limited hardiness however, has been a major limitation so far, but since the fall 2013 propagates the promising Belarusian variety ‘Loiko 63’ in Lars Westergaard's nursery outside Odense in Denmark. OLoiko 63´ originates from a trial cultivation in Belarus and 2003 planted 100 seedlings in Sweden. The seedlings were taken to Sweden by plant enthusiast Ove Johansson living in Indal outside Sundsvall and the seedlings were distributed across the country. Ove's son Louis has also written a very interesting book called " Grow exotic in your garden” (2007) where he coined the term "extreme growers' I can somehow identify with.
The seedlings from Belarus show excellent hardiness and gave a harvest in the Sundsvall region already in the autumn 2008. To our great joy comes a clone ‘Loiko 63’ to come to Stjärnsund in the spring and enrich our collection of nut trees. Genuine walnut gives fruit after about five years. Young trees can produce 2 to 5 kg of nuts per year, while the trees 10 to 20 year-old gives between 15 and 50 kg of nuts per year, and 1,6 to 5 tonnes per hectare per year .
In addition to the Loiko nuts, Manchurian walnut is considered (Juglans mandshurica) be the hardiest species in the genus. It thrives well in cultivation zone 5 and there's even copies of Jämtland, but the nuts are very brews, with small grains that break easily when the nut is cracked. In the colder parts of Sweden, it may be an option for lack of other species, or until varieties of the same quality as the Loiko nuts have become more widespread.
Black walnut (Juglans cinerea) cultivated as park trees in many Swedish cities and the species is considered to be resistant to cultivation zone 4 or 5. The nuts are very creamy and tasty (the English name is Butternut), but brews and even these nuclei break easily when it breaks. There are cultivars from North America that exhibit better properties, so that Booth, Beckwith and Bear Creek available on the European market. Butternut gives fruit after 5-8 years after they were planted and the relatively short-lived trees (80-90 years) gives 14-23 kg of nuts per year.
Heartnote (Juglans ailanthifolia var. cordiformis) is a subspecies of the Japanese walnut (Juglans ailanthifolia) with heart-shaped, very tasty nuts of many nötkännare considered the most delicious walnut. The species is possibly resistant to cultivation zone 4 and the variety 'Kalmar' has shown very good properties in Danish experimental garden . I have just got hold of a seedling from a tree in Singapore and have had the variety 'Feed Maier' for two years, who has done really well in the forest garden. Name Places of Heart notes begin to produce nuts for five years after planting and then produce on average 2,3 kg of nuts per tree. After 10 years, they produce 23 kg per tree, and when they are older than 15 years after being its maximum production on average 34 kg of nuts per tree.
Buartnut (Juglans x bisbyi) is a hybrid between Butternut and Heart notes, which is believed to reconcile the gray walnut hardiness with hjärtnötens culinary properties. We planted two copies of this hybrid a few years ago, but unfortunately they suffered any DECAY DAMAGE and withered down shortly after planting out. So far we have not been able to get hold of new seedlings.
Black walnut (Juglans nigra) descended like Butternut from North America and has been cultivated there for a very long time. It has a delicious flavor and some cultivars released the kernel freely and in one piece, Thus, without falling apart into a thousand pieces, but it is also by far the most brews walnut. The shell is so hard that it was used as a heat shield in the first American space shuttle, and even today used the crushed shell as abrasives in industrial contexts. Seedlings of black walnut gives fruit only after 12-15 years and then produce around 8 kg of nuts per year. Mature trees can after about 50 year give 100 kg of nuts per year. Grafted trees can produce fruit after a few years .
All walnuts need a warm, well-drained habitat, while they must be able to access ground water with their long pålrötter that can be three to five feet deep with full-grown trees . Therefore, it is perhaps not surprising that in their natural environment often occur on slopes near rivers. In the first years investing walnuts most on developing pålrötterna and they are therefore very sensitive to transplanting. They do not like to grow on soils with low pH and thrives best in soils with pH 6,5 or higher.
Walnut leaves contain a herbicide called juglone that inhibits the growth of other plants. Juglonets effect is relatively limited regional, but apple trees show great sensitivity to the poison and should be planted away from walnut trees. A selection of plants that can tolerate juglone and which therefore lends itself to co-planning with walnuts shown in the table below. A more detailed summary that distinguishes between three different time and that also includes annual crops and animals are in a scientific article from 2008.
Juglonresistenta plants (from ).
|Swedish name||Botanical name|
|Jerusalem artichoke||Helianthus tuberosus|
|Day Lily||Hemerocallis fulva|
|Spanish chervil||Myrrhis odorata|
|Jätterams||Polygonatum biflorum was. Commutator|
Walnuts are usually wind-pollinated and requires a different kind (or species) to give fruit. Some individuals are self-pollinating or develop the ability to pollinate themselves when there are no other walnut trees near. Other individuals can put fruit without pollination has occurred, a phenomenon called apomixis .
Both hazelnuts and walnuts are among the fat-rich nuts and in the next post we will look at the chestnuts, belonging to the starchy nuts.
 Crawford, M., Nut Crops – Appendices, 2012.
 Westergaard, L., 2013 [personal communication].
 Mohn, C.P.F.H.G.E., The modern silviculture of Juglans regia L.: A literature review. The Natural Resources., 60(3): p. 21-34, 2009.
 Jacket, D. and E. Toensmeier, Edible forest gardens. White River Junction, Vt.: Chelsea Green Pub. Co., 2005.