Walnut treesWalnuts are perhaps the healthiest of all nuts, and in the right conditions can be grown successfully in the UK.
How to choose Walnut trees
The combination of healthy unsaturated fats, high levels of antioxidants, and rich vitamin content has increased interest in growing nuts in the garden or home orchard. Somewhat surprisingly the humble Walnut is turning out to be perhaps the healthiest of all nuts, thanks to its super-abundance of antioxidants.
Walnuts are essentially large spreading trees, and over the course of several decades will slowly grow to a height of between 6m-12m (20ft - 40ft) depending on the variety. The ultimate size is quite variable, dependent on the local soil quality and climate.
All our walnuts are of the fruiting species, Juglans regia, but most are grafted on to rootstocks of a related species (Juglans nigra, the Eastern Black Walnut*) which encourages earlier fruiting. Even so they grow at a leisurely pace and regular nut production is unlikely to start before 4-8 years. However like most slow-growing trees, Walnuts are very long-lived. Growing Walnut trees is therefore a long-term undertaking - but a worthwhile one.
Some Walnut varieties are self-fertile, with both male catkins and female flowers occurring on the same tree. In this respect Walnuts are similar to Hazelnuts rather than Almonds (which are more closely related to plums). The potential for self-fertility arises when the timing of both the flowers and catkins co-incides. Self-sterile Walnut varieties are those where the timing of the flowers and catkins does not overlap. Again, as with Hazelnuts, it is often a good idea to plant two Walnuts of different but compatible varieties if you have the space. Walnuts have an advantage over other nuts in that the pollination process occurs very late in the spring so is less affected by the poor early spring weather which often occurs in the UK.
Walnuts are relatively untroubled by diseases, but pruning is best avoided. If you must prune (e.g. to remove crossing branches), do so in mid-summer.
*Juglans nigra grows a bit more quickly than the fruiting species Juglans regia and can reach up to 20m-30m (60ft-100ft) over time - although in the UK they are likely to reach only the lower end of this scale. The nuts are of inferior quality to Juglans regia, but these and other walnut species are grown for the excellent quality of their timber.