Detailed Explanation of Key Techniques for Cherry Cultivation and Seedling Raising

1 Selecting the nursery site

For raising cherry seedlings, a flat site or a gentle slope with a gradient of less than 5° is preferable (gentle slopes drain easily and do not waterlog); slopes facing south, southeast or southwest are all acceptable. For raising seedlings on flat ground, sandy loam soil should be chosen, the groundwater level must be below 1.5m, and the soil layer should be deep, loose and fertile with good drainage. Cherry seedlings are susceptible to damping-off during the seedling stage, and compacted, overly moist soil leads to severe disease. Avoid raising seedlings on land that previously grew cherry seedlings or was a cherry orchard.

2 Land preparation and fertilisation

Before preparing the nursery land, apply 3000-4000kg of high-quality farmyard manure per 667 sq m, then deep plough and rake level, forming beds 1.0-1.2m wide and less than 50m long. In places prone to waterlogging in summer, raised-bed seedling raising can be used (bed height 20cm, width 80cm, with a 30cm-wide drainage ditch between beds).

3 Using suitable propagation methods

3.1 Division propagation method. Division propagation is a commonly used method for cherry seedling raising, and large seedlings can be produced in the same year. In practice, three methods are commonly used: mound layering, horizontal layering and direct division.

3.1.1 Mound layering method. In late autumn or spring, pile soil 30-50cm high around the base of a selected mother tree to encourage the suckers arising from the trunk base to root and form new plants. In the following autumn or the 3rd spring, cut off the rooted plants and take them out, to be planted directly in the orchard or used as rootstock. Generally, each mother tree can yield 5-10 new seedlings per year.

3.1.2 Horizontal layering method. Select suckers close to the ground with more side branches, press them horizontally into a trench, fix them with wooden hooks, then fill with soil and firm it down. In autumn or the following spring, cut off the rooted layers and separate out new plants.

3.2 Cutting propagation method. Cherries root relatively easily from cuttings, and two methods can be used: hardwood cuttings and greenwood cuttings. Hardwood cuttings are more widely used in practice. Hardwood cuttings should be taken in spring when the sap is flowing; greenwood cuttings are taken from June to late July. For greenwood cuttings, use semi-lignified new shoots of the current year, 0.3cm in diameter; too thick and they root poorly, too thin and nutrition is insufficient. After collection, cut immediately into stem sections about 15cm long, keeping only the top 2-3 leaves and removing all the rest, and insert them as soon as they are collected. When taking cuttings in spring, the cuttings can be covered with soil or with film. When using film, the upper end of the cutting can be wax-sealed for 2cm. To improve the rooting rate, before inserting the cuttings the lower end (about 5cm) can be soaked in 100mg of rooting powder or 50-100mg of indolebutyric acid solution for 4-5h, then inserted immediately after removal; roots form 20d after insertion. When the new shoots reach 20cm, water and top-dress to promote seedling growth. Before the rainy season, earth up 5cm around the base of the seedlings. By autumn the seedlings can reach 80cm in height and 0.8cm in thickness, meeting the standard for grafting and leaving the nursery.

3.3 Grafting propagation method. The branches of sweet cherry generally do not readily produce adventitious roots, so grafting propagation is mostly used in practice.

4 Brief introduction to grafting propagation

4.1 Selection of rootstock varieties. Currently commonly used rootstock types include Agate cherry, Nanking cherry, dwarf cherry, grass cherry and mountain cherry, among others. Since virus disease has not been found in mountain cherry seedlings, their seedlings are mostly used as sweet cherry rootstock in practice.

4.2 Seed collection and seed treatment. The fruit development period of cherries is short, the embryo develops incompletely, and after drying it easily loses viability; therefore cherry seed treatment differs from that of other fruit trees. Seeds used for seedling raising must be harvested only after the fruit is fully ripe. After harvest, immediately remove the flesh, take out the stone, rinse clean with water, dry in a shaded place, then stratify in sand immediately. For sand stratification, first mix the seeds with moist sand at a ratio of 1:5. The moisture of the sand should be such that it forms a ball when squeezed in the hand and breaks apart when the hand is opened. The stratification site should be chosen in a shaded, high and dry place; dig a storage trench 50cm deep and 80-100cm wide, first spread a 10cm-thick layer of moist sand on the bottom, then place the mixed moist sand and seeds into the trench, generally about 40cm thick, cover with 10cm of moist sand, then cover with fine soil or grass to retain moisture, and place tiles on the very top to prevent rain.

4.3 Sowing and management methods. The same as the conventional methods for raising plum and apricot rootstock seedlings.

4.4 Grafting methods

4.4.1 Cleft grafting method. For grafting before bud break in spring, methods such as cleft grafting, cut grafting, side grafting and whip-and-tongue grafting are preferable.

4.4.2 Bud grafting method. In the cherry growing season, T-shaped budding and budding with wood can be used, with budding with wood giving the better result.

The specific operation of budding with wood is: about 1.5cm above the bud to be grafted, make a 45-degree slanting cut on the scion to 2/5 of its thickness. Then start the knife about 1.5cm below the bud, cut vertically downward along the xylem until it meets the first cut, with a little wood attached, and remove the bud. Next, on the rootstock 3-5cm above the ground, choose a smooth surface and cut in the same way as for preparing the bud, making the cut slightly larger than the bud surface. Then press the bud against the cut surface of the rootstock, align the cambium, and bind tightly with plastic film strips. Take care to expose the bud and the leaf stalk.

4.5 Management of grafted seedlings

4.5.1 Do not water within 20d before and after grafting; if cherry grafts are rained on or watered after grafting, gummosis is easily caused, affecting survival.

4.5.2 From bud break of the grafted bud until before July, top-dress with ammonium sulphate or urea 2-3 times, applying 105-150kg per hectare, and pay attention to irrigation. During seedling growth, carry out timely intertillage and weeding and control pests and diseases.

4.5.3 Loosening the binding. After summer budding succeeds, loosen the binding in good time to prevent the binding material from cutting into the bark and causing gummosis; loosening should be done when the grafted bud is 10cm long.

4.5.4 Cutting the rootstock. For bud-grafted seedlings, the rootstock can only be cut when buds break in spring. Cutting the rootstock too early makes the rootstock stub dry back downward and kills the grafted bud. Cut the rootstock 1cm above the grafted bud.

4.5.5 Tying. When the grafted bud grows to 20-30cm, set up a support in good time, and tie it 2-3 more times afterwards.

4.5.6 Pinching. When the seedling is 30-40cm tall, pinch it back leaving 20-30cm, so that flower buds can form the following year and it can flower and fruit in the 3rd year.

4.5.7 For grafted seedlings, remove the earth piled up in good time. For those kept moist with wet sawdust in plastic bags, when the grafted bud is 5cm long, open the bag for ventilation.

4.5.8 In areas with spring drought, to promote vigorous early growth of cherry seedlings, irrigate, top-dress and intertill and weed in good time according to rainfall conditions, to promote seedling maturity.