How are hawthorn trees cultivated and managed in high-altitude cold regions?

1 Selection of hawthorn varieties suitable for cultivation in high-altitude cold regions Choosing varieties suited to local natural conditions is the key to successful hawthorn cultivation in high-altitude cold regions. When selecting varieties, strong cold resistance and adaptability must be given top priority, while also paying attention to excellent quality and so on. In a hawthorn orchard, 2 to 3 varieties with the same or similar flowering periods should be planted in separate rows; cross-pollination can significantly increase the fruit-setting rate. At present, the hawthorn varieties suitable for cultivation in high-altitude cold regions (annual effective accumulated temperature at ≥10°C of 2600-2700°C) are mainly Dawang, Shuanghong and Fushanzha.

2 Propagation methods of hawthorn nursery stock The hawthorn trees planted must be grafted seedlings. After sowing seeds of wild hawthorn and raising seedlings, when the seedlings grow to a stem diameter of more than 0.5cm (at 5cm above the ground), graft using tender buds of excellent varieties from July 20 to August 20. Alternatively, in the spring of the 2nd year around Qingming, hard branches can be used for cleft grafting or the hard-bud method can be used for grafting. To save costs, wild young hawthorn seedlings can also be dug up and planted directly in the production orchard in spring or autumn at the row and plant spacing. Seedlings that survive spring planting can be grafted with tender buds in July. For wild hawthorn nursery stock planted in autumn before the ground freezes, before freezing the seedlings must be earthed up to more than 30cm or laid flat on the ground and completely covered with soil; around Qingming of the 2nd year, remove the soil and select excellent edible varieties for hard-branch grafting or carry out tender-bud grafting in July. Seedlings grafted with hard branches can bear fruit more than 1 year earlier than those grafted with tender buds, and can also save the cost of buying nursery stock.

3 Cultivation techniques In fertile flat land, row and plant spacing is mostly 4m x 4m or 5m×4m. In hilly land and mountain slopes, row and plant spacing is mostly 4m x 4m or 4m×3m. Whether on sunny mountain slopes, east-facing slopes or southeast-facing slopes, the rows should all run north-south, which favors ventilation and light penetration between hawthorn trees.

Dig holes before planting seedlings. In fertile soil, the hole length, width and depth should be 50cm×50cm×50cm; in poor soil, the holes can be enlarged to 70cm×70cm, with a depth of 50-60cm. Before planting, be sure to backfill with decomposed fertile high-quality soil and farmyard manure to ensure sufficient nutrients for the early growth of the seedlings. For 1- to 2-year-old trees, field management must be strengthened, and every possible means should be used to ensure the seedlings survive. In summer, weed and loosen the soil in time, and in drought, water in time if conditions permit. Before the ground freezes, the tree trunks should be whitewashed or wrapped with straw or earthed up to protect the young trees so they can overwinter safely. Hawthorn trees generally rarely undergo flower and fruit thinning, and the load per tree is large; if fertilizer, water and other technical measures are managed loosely, this will affect the normal development and growth of the fruit trees. Management during the growth period mainly includes: plowing the open spaces between rows every year, and plowing the tree plates every 1 to 2 years; before each plowing, if conditions permit, it is best to first spread farmyard manure and then plow. The best farmyard manure is poultry manure and pig manure, deer manure, plant ash, hair, poultry feathers and so on. Apply nitrogen fertilizer reasonably, and increase the amount of phosphorus and potassium fertilizer applied later. For trees more than 10 years old, in early May apply 250g of urea per tree to supplement the nutrients needed for tree growth, flowering and fruiting. In mid-July, apply 400-500g per tree of a mixture of nitrogen, phosphorus and potassium fertilizer in a ratio of 2:4:4 to promote fruit enlargement and improve fruit quality. Fertilizer should be applied into several dozen holes (pits), with a depth of no less than 15cm. The distance between the fertilizer holes (pits) and the tree should be 80-100cm. After fertilizing, cover with soil, and if conditions permit, water immediately to speed up the dissolution of fertilizer and promote rapid absorption by the root system. In summer, prune useless vigorous branches and dead branches at any time. For some side branches whose opening angle is insufficient, be sure to pull them with ropes or prop them with wooden sticks so that they reach the required angle.

4 Pest and disease control The main insect pests of hawthorn trees are spider mites and the peach fruit moth. Spider mites mainly damage tender buds, tender leaves and flower buds. During the occurrence period, choose targeted pesticides and use them according to the instructions. The peach fruit moth can make the fruit lose its edible value and cause large-scale yield reduction. The timing of the occurrence of the fruit moth is related to the temperature and moisture at the time; the occurrence and control timing can refer to the occurrence patterns of the fruit moth on apple trees and pear trees, and pesticides such as Taoxiaoling, phoxim and dichlorvos can be used for control.

5 Training and pruning The training and pruning of hawthorn trees basically combines the best training and pruning techniques of pear trees, apple trees, plum trees and peach trees. When the open-center tiered form is used, it is roughly the same as the training and pruning methods for apple trees and pear trees; when the multi-main-branch natural round-headed form or natural open-center form is used, it is basically similar to the training and pruning methods for plum trees and peach trees. Hawthorn trees have weak trunk dominance, and the central leader is prone to leaning, deviating, or developing an unbalanced crown. For trees more than 10 years old, once the central leader becomes weak or deviates, the extension branch of the central leader is often replaced to correct it. When the central leader deviates and leans severely and is difficult to train, its natural growth tendency should be followed, the central leader should be removed, and it should be changed to a natural open-center form, leaving 3-4 main side branches on the whole tree; at this time the tree form is completely the same as the training and pruning methods for peach trees and plum trees. Improper pruning of hawthorn trees can very easily cause the fruiting position to move upward. In order to stabilize yield and maintain a good tree form, during pruning the fruiting mother branches should be retracted in turn. When rejuvenating those branch groups that have borne fruit for many years and become pendulous, relatively heavy retraction should be carried out on 3- to 5-year-old branch sections. In an on-year, more mother branches should be thinned so that the ratio of fruiting mother branches to vegetative branches remains at a minimum of 1:1 (or 2:1); at the same time, supplementary pruning should be carried out at the flower bud stage to thin out some flower buds on weaker branches. When the canopy is seriously crowded, some large branches should be thinned or retracted, and some vegetative branches should be cut off, so that the whole tree is well ventilated and illuminated.