3DescriptionWalnuts are rounded, single-seeded nuts (stone fruits) ,the walnut tree commonly used after fully ripening. Following full ripening, the removal of the husk reveals the wrinkly walnut shell, which is usually commercially found in two segments .Perennial woody cropDeciduous fruit treeBotanically Dicot plantAccording to use nuts (Stone Fruit)Ozone sensitivity: tolerant
4Leaves and BudsEnglish walnut leaves are compound and arranged alternately along the stem.The leaf is composed of 5 to 9 leaflets, each reaching a length of 2 to 5 inches.The margins of the English Walnut leaflets are entire (teeth absent).
5FlowerAll Juglans are monoecious, bearing male and female reproductive organs on separate flowers on the same tree. Although J. regia is self-fertile, it is heterogamous, either protandrous or protogynous depending on cultivar.Catkins (male inflorescences) are borne laterally on 1-yr wood, and pistillate flowers are borne terminally or laterally (newer cultivars) on current season’s wood in spikes of typically 2-3 flowers.
6FruitNuts are borne singly or in clusters of 2-3 on shoot tips. A green, fleshy shuck surrounds the nut, which splits irregularly at maturity. The shell is rough, wrinkled or furrowed, and thin. Nuts containing two kernels separated by a thin, papery central plate extending from the inner layer of the shell.
7BarkBark is thick, ridged, very dark brown, with deep diamond-shaped furrows.
8PollinationWalnuts are similar to pecans in that the time of pollen shedding does not always overlap well with the time of female flower receptivity to pollen.Most walnuts are self-fertile, they sometimes require another cultivar for pollination since the timing of the functions of male and female flowers is different.
9Walnut roots contain juglone which inhibits growth of some plants beneath the tree. Plants such as tomato and evergreens are quite sensitive to juglone.Root System - Produces a deep, extensive taproot, which makes transplanting difficult.
10Types originated in Persia, originated in eastern North America. The two most common major species of walnuts arethe Persian or English Walnutthe Black Walnut.originated in Persia,The commercially produced walnut varieties are nearly all hybrids of the English walnut.originated in eastern North America.The Black walnut is high flavor, but due to its hard shell and poor hulling characteristics it’s not grown commercially for nut production.
12English walnut and Black walnut differ in the number of leaflets, the shape of the leaflets, and the leaflet marginBlackEnglishblack walnut leaves have a greater number of leaflets (15-23)black walnut leaves are generally smaller and narrower in shape.Black Walnut leaflets have toothed marginsEnglish walnuts (5-9).English walnut leaflets have more oval shaped leavesEnglish walnut leaflet margins are entire.
14Soils and ClimateThe best soils are deep, well-drained silt loams with pH 6 to 8 Persian walnuts are best adapted to Mediterranean climates, with dry, hot summers and mild winters. Cold hardiness is a major limiting factor for Persian walnut.The Chilling requirement is 400 to 1600 hr.
15Propagation Common methods are whip grafting, ring or patch budding. This is commonly done in spring on 1 year seedling rootstocks in nurseries, but some growers prefer to plant ungrafted stocks and graft in the orchard, after the rootstock becomes established.
16Plant facts Height: 60 to 70 feet Spread: 50 to 70 feet Crown shape: roundCrown density: moderateGrowth rate: mediumWalnut trees usually are planted about 30 feet apart
17RootstocksPersian walnut seedlings (J. regia) are the most popular rootstock worldwide, and in areas where blackline disease is a problem.‘Manregian’ is the selection most tolerant of blackline disease. Trees usually lack vigor and yield efficiency like in California when propagated on this rootstock, so Northern California black walnut (J. hindsii) is the most common stock for Persian walnut in California.‘Paradox’ (J. hindsii x J. regia) is a hybrid of Persian and Northern California black walnut, and generally superior to its parents in several traits
18Maturity Harvest Method walnuts are harvested at the beginning of shuck split, when the seed coat is a light color .Harvest Methodtrunk or limb shakers are used depending on tree size.A windrow machine places the nuts into narrow rows to be picked up by a sweeper.Nuts are collected in large boxes and taken to the processing plant.
20Postharvest HandlingFreshly harvested walnuts are removed from hulls and dried in forced-air dryers at °F until 8% moisture content is achieved. In-shell nuts are bleached and sold fresh.
21StorageWalnuts, like other nuts tree, must be processed and stored properly. Poor storage makes walnuts susceptible to insect and fungal mold.The temperature for longest storage of walnuts about -3 to 0o C and low humidity — for industrial and home storage.Temperatures above 30 oC, and humidities above 70% can lead to rapid and high spoilage losses.Dried nuts can be stored for about 4 months at room temperature before becoming spoilage, & for 1-2 years when stored in the freezer.
22Dietary value, per 100 gram edible portion Water (%)3-5Calories651Protein (%)14.8Fat (%)64Carbohydrates (%)16Crude Fiber (%)2.1Vitamin A0.6Thiamin, B124Riboflavin, B28.1Niacin5Vitamin C4.4Calcium12Phosphorus48Iron31Sodium—Potassium9.6