What are the excellent foreign walnut varieties?
1. Chandler
Source and distribution: native to the United States, it is a hybrid progeny of Pedro XUC56 - 224. It is the main early-bearing walnut variety planted in the United States and was introduced into China in 1984.
Economic traits of the fruit: the nut is large, with an average three-diameter measurement of 4.4 cm and an average single-nut weight of 12.86 g. The nut is heart-shaped, with a smooth shell surface and a tight suture line. It is easy to obtain whole kernels, and the shell is 1.5 mm thick. The kernel rate is 49%; the kernel is plump and full, creamy yellow in color, fragrant in flavor, and of excellent kernel quality.
Growth and fruiting habits: the tree vigor is moderate, the tree posture is relatively upright, the branchlets are stout, and the internodes are medium. It leafs out late and is protandrous. It is a medium-early maturing variety. The rate of lateral mixed buds is 80%-90%. It is suitable for planting in areas with an annual average temperature above 11°C and a growing period of more than 220 days. Grafted trees begin bearing fruit in 2 years, form male inflorescences after 4-5 years, and have medium yield.
This variety has strong adaptability and is relatively tolerant of high temperatures. It leafs out late, resists late frost, and suffers relatively light damage from black spot disease. It is suitable for planting on deep soil with irrigation conditions.
2. Qingxiang
Source and distribution: selected by Shimizu Naoe of Japan from a seedling population of walnuts in Nagano, Japan; it belongs to the late-bearing variety type. Hebei Agricultural University introduced it into China and promoted it.
Economic traits of the fruit: the nut is large, with an average nut weight of 14.3 g; the nut is oval, large and attractive in shape, and the suture line is tight. The kernel rate is 52%-53%, the kernel color is light yellow, the flavor is sweet and fragrant, there is no astringency, and the kernel quality is good.
Growth and fruiting habits: the tree is medium in size, the tree posture is semi-spreading, growth is relatively vigorous in the young tree stage, and the tree vigor stabilizes after fruiting. It is protandrous and a late-maturing variety. Generally only the terminal buds can set fruit, fruiting branches account for more than 60%, the ability to bear fruit continuously is strong, the fruit-setting rate is above 85%, the branching rate is 1:2.3, and the double-fruit rate is high. It has strong high-yield potential. After grafting, it bears fruit in 3 years and reaches high yield in 5 years, producing 278 kg of nuts per 667 sq m. In the Baoding area of Hebei, it buds and unfolds leaves in early April, sheds pollen from male flowers in mid-April, and reaches the peak of female flowers in late April. It matures in mid-September. It sheds leaves from late October to early November.
This variety has strong resistance. It is frost-resistant, flowers late, and avoids frost damage. It has relatively strong resistance to anthracnose and black spot disease. It has no strict requirements for soil. It is suitable for large-scale development in North China, Northwest China, southern Northeast China, and some areas of Southwest China.
3. Hartley
Source and distribution: discovered in the United States in 1915 by Mr. and Mrs. John Hartley in their private walnut orchard in the Napa Valley; it is the most widely cultivated variety in California, United States. It belongs to the late-bearing walnut variety type.
Economic traits of the fruit: the nut is large, with an average single-nut weight of 13.56 g. The base of the nut is wide and flat, and the top is pointed, resembling a heart shape. The suture line is tight. The kernel rate is about 45%, and 90% are light-colored kernels. Hartley is the main variety sold in shell after bleaching and washing.
Growth and fruiting habits: the tree is medium to large, the tree posture is semi-spreading, and it grows very vigorously on fertile soil. The fruit-setting rate of lateral buds is about 10%. It begins bearing fruit relatively late, but the yield is very high in the full-bearing period. It is protandrous and matures in mid-September.
This variety shows high yield in California, United States, has light-colored kernels, and is not easily damaged by codling moth and black spot disease. It is susceptible to deep bark cankers; when water is unbalanced or the soil is poor, deep cankers are a limiting factor in cultivating Hartley. It can achieve high yield only when planted on deep, fertile, well-drained soil and given reasonable irrigation. It is suitable for cultivation with large canopies and wide spacing.