Edible nuts mostly come from trees (peanuts are an exception); and often need 5 years to produce a crop (sometimes up to 10 or 15 years).
When you select a site take into consideration the amount of space required, likelihood of frosts and strong windy conditions, as most nut trees are either intolerant of frosts or experience heavy crop losses through hard winds.
Most nut trees (excluding hazelnuts, filberts and almonds) grow into large trees that require adequate space.
Most nut trees (walnuts excluded) need two trees to cross pollinate (otherwise they do not produce a crop).
To provide adequate pollination, you need to plant different varieties of a species (or know there is one in a nearby property).
Because nut trees are generally wind pollinated and most will require a cross pollinator planted close by (within 30m or so) for successful pollination.Climatic conditions required to produce nuts varies depending on species. Some species such as macadamias, pecans and cashews need long hot summers to mature.
Others such as walnuts, being prone to sunburn, need cooler conditions.
Commonly Grown Varieties of Nuts
Almond
Prunus dulcis
Almonds prefer a sunny warm site, well drained soil, not alkaline and 6 x 8m spacing (can be slightly closer). Irrigate and feed regularly to achieve good results, although almonds are more drought tolerant than other Prunus.
They need a frost free situation in late winter and early spring, as frost kills young fruit and flowers. Cross pollination is essential.
Cross pollination with varieties such as Californian Papershell, Strouts Papershell and Ne Plus Ultra are successful. Also Challeston, Johnston’s Prolific and Brandis Jordan cross pollinate with each other.
Almonds in blossom are a delight to both humans and bees. Almonds have a high magnesium content which is reputed to relieve stress.
Cashew
Anacardium occidentale
The cashew is a tender tropical evergreen tree. Most commercial production is from Africa, India and Northern Brazil. Propagated by seed, layering and grafting, it will only grow in warm to hot climates. Cross pollination is not necessary.
The fruit of the cashew is fleshy, fragrant and slightly bitter and can be eaten raw or cooked. The nut is a kidney shaped projection extending from the tip of the fruit. This nut must be roasted before eating to get rid of poisonous oil in it.
Chestnuts
Castanea sativa
Chestnuts need good rainfall and cooler climates in mountain areas, shelter form the wind and deep well drained soils. They are self-sterile and require more than one variety near by for cross pollination. In areas below 75cm annual rainfall young trees will require irrigation. They are affected by hot summer temperatures.
Chestnuts are a cousin of the oak tree and family Fagaceae. Japan and Italy are the largest producers of these nuts.
Grafted trees take 3 to 6 years to crop while seedlings take up to 20 years. Fruit ripens over a period of time through autumn. Nuts are beaten out of the husks and marketed at once or else prepared for dry storage. Once the nut has dried, to store, pack in alternate layers of dry sand in a cool dry position. They will store this way for several months.
Filbert
Corylus avellana and C. maxima
This relatively small, deciduous tree or shrub has a nut that is very similar to the Hazelnut. They are grown in Turkey, British Columbia and Canada. They are suited to a shade site but un suited to warm areas. They require good drainage, fertile soils. They propagate by seed, layering or grafting. Trees can live for up to 150 years. They start to yield in their 4th or 5th year but takes up to 15 years to come into full bearing. They need crosspollination.
American Hazelnut
Corylus americana
From the same Genus as the Filbert, the American hazelnut too requires cooler climates. They do not like to be affected by too much sun. They are known to be grown with the Filbert to provide cross pollination. Male and female flowers are on the same tree, but do not open at the same time, so many cultivars are planted to allow for optimum pollination.
Macadamia
Macadamia integrifolia and M. tetraphylla
The Macadamia comes from Australia where is grows in the warmer climates of coastal south Queensland and Northern NSW. They are also grown on a large scale in South Africa and Hawaii. They can grow in the cooler climates, however their production drops. They are grown from grafted seedlings most often in cultivation, to create the best nuts for roasting. Though they will sprout easily from seed, they are not often used. They will start producing crops at 5 years, sometimes earlier. They will harvest from March to August, though there will be the odd drop over the year.
They require free draining, fertile soils, plenty of sun are usually pollinated by native bees. M. tetraphylla is thought to be more successful in a cooler climate and M. integrifolia is better suited to roasting.
Peanut
Arachis hypogaea
Peanuts are only suited to the subtropical regions of the world, accept where areas are protected from frost. They are a low growing, leguminous plant and produce nitrogen from bacterial nodules on the roots.
They are grown in broad acre faming and are planted in spring, 5-8cm deep in light soils, 3-5 cm deep if heavier. They do well with an initial feeding and require a soil that is no more than pH 6-6.5, an application of lime can be useful if so. In areas with an annual rainfall of less than 60cm, the crop should be irrigated.
Nuts are ready for harvest when the plant starts to yellow and growth slows. When it is time for harvest, inspect the crop frequently as the nuts do not ripen all at the same time. They are an annual crop and need to be re-planted each season.
It is important to note that crops need to be rotated to reduce soil borne diseases in the same planting areas. India is the highest producer of peanuts, followed by China and Nigeria.
Pecan
Carya illinoiensis
A well known and established crop from the USA, they are a deciduous tree and can grow to 50 meters high. They require a long frost free growing season with hot days and warm nights to mature the nuts properly. They also need a cold winter or they will not produce flower. They require a deep, well drained soil with no hard-pan sub soil layers to find as they also have a long tap root system.
They need a pH of 6-6.5, are very susceptible to zinc deficiency in the soil and may need foliar spays of Zinc sulphate to keep production high. Full sun is essential.
Propagation is by either seed, softwood cuttings, budding or grafting.
Pistachio
Pistachia vera
Worthwhile only in warmer climates, the Pistachio is a small to medium deciduous tree that can live for several hundred years. It needs long hot dry summers, though it can survive winter temperatures well below freezing. While they will survive on poor soils, they yield best on deep well drained sandy loams. They can also do well on alkaline soils.
Both male and female plants are required. One male to every 10-12 female trees are needed. Pistachios are generally grafted onto rootstocks of a different species (P. atlantica is preferred as P. vera is less vigorous)
For best results, feed annually with a nitrogen fertilizer.
Walnut
Juglans seiboldiana
Walnuts are from the USA cooler parts of the and not suited to warm or humid climates. Commercial crops are grown in the North of the USA and cooler parts of California. They prefer deep fertile soils and will require 18meters between trees in cooler areas and closer in warmer ones.
Walnuts can grow to 30 meters or more tall, and are deciduous. They have very large and very deep root systems.
Propagate by seed or grafting onto seedlings.
Normally takes 5 years to commence cropping. One large tree can produce a wonderful crop, provided they have 800 hours of chilling in winter at temperatures of 10°C.
The timber from the Walnut also makes a lovely veneer for building cabinets.
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