Detailed Explanation of Key Points of Rapid Propagation Techniques for Tree Peonies

The tree peony is a traditional famous flower of our country and is deeply loved by people. If its rapid propagation problem can be solved and production costs reduced, it will greatly meet market demand. Propagation methods for tree peonies include division, grafting, cuttings, layering, and so on. Comparatively speaking, grafting is still the better method for tree peony propagation. However, grafting in the narrow sense cannot solve the problem of rapid propagation of tree peonies. In production practice, after years of exploration, the Mangshan Flower and Seedling Farm in Luoyang City, Henan Province, improved the traditional grafting method and formed a complete set of standardized rapid propagation techniques for tree peonies, accelerating the development of superior varieties. The key points of this technique are introduced below.

1. Screening Varieties

At present, our country has more than 600 tree peony varieties. Through market surveys and observation of the biological characteristics of tree peonies, the farm selected 4 series of varieties from the tree peony variety groups and made them into a complete matching set. First, varieties with bright flower colors, abundant flowers, loose "flower openings" (easy to bloom), easy propagation, and well-developed root systems were selected as the forcing-cultivation variety series, such as Luoyang Hong, Hu Hong, Wulong Pengsheng, Rou Furong, Si Helian, Zhusha Lei, and so on; second, varieties with bright flower colors, abundant flowers, and short plant type were selected as the potted variety series, such as Hu Hong, Taohong Xianmei, Shanhu Tai, Yipin Zhuyi, Wujin Yaohui, and so on; third, varieties with bright flower colors, abundant flowers, long pedicels, and strong sprouting ability were selected as cut-flower varieties, such as Zhao Fen, Shiba Hao, Yanzhi Hong, and so on; fourth, varieties that possess all eight major color systems, have rich flower types, are relatively rare and precious, have strong adaptability, and have good visual effects were selected as the variety series for flowerbed planting or for establishing tree peony gardens. In this regard, the farm abandoned the "large and complete" approach and selected only more than 100 premium tree peonies as "retained varieties."

2. Establishing a Scion Collection Nursery

Grafting propagation of tree peonies must have sufficient scions and rootstocks. For this reason, a scion collection nursery must be established for the purpose of cutting scions. To establish a scion collection nursery, a plot with loose, deep, and fertile soil must be selected, and the plant and row spacing must be large (1×1). After the selected superior tree peony varieties are planted in the autumn of that year, all branches above ground are cut off (this is the so-called "stumping"), in order to stimulate the adventitious buds at the junction of roots and stems to sprout the following year and grow into short branches (that is, scions). Fertilizer and water management for the "mother plants" in the scion collection nursery must be strengthened. In this way, scions can be cut once every autumn, and the short branches will become more and more numerous.

3. Timing Selection

Grafting propagation of tree peonies is extremely time-sensitive. Tests show that in the central part of the Yellow River basin, early September to early October is the best season. If the best grafting time is missed, the survival rate will decrease as the season is delayed. At this time, if rainy weather occurs, grafting must still be rushed to be carried out, and it can be done indoors, but care must be taken to place the grafted plants neatly and pay attention to ventilation (this still does not affect the healing of scions and rootstocks). After the weather clears and the soil is suitable for cultivation, planting is carried out. Generally, trench planting is used, with a trench width of 20 cm and a depth of 30 cm. The planting spacing is about 15 cm between plants and about 35 cm between rows.

4. Improving Labor Organization

In the case of large-scale production, to improve the survival rate of tree peony grafting, seizing the timing is certainly important, but other factors cannot be ignored either, such as improving the grafting skills of operators and strengthening the sense of responsibility of grafters. Because time is tight, tasks are heavy, and there are many varieties, special attention must be paid to the arrangement of labor organization. The farm's approach is to hire surplus rural labor from the local area, who may take up their posts only after strict technical training. The farm headquarters uniformly provides scions and rootstocks. Generally, 2 people form one grafting group. After each batch is grafted, the grafters plant them at designated locations, and the following year remuneration is paid according to the grafting survival rate (only living expenses are issued at the time of grafting). Because labor organization was improved and the responsibility system was strictly enforced, the farm can complete the task of grafting 100,000-150,000 tree peonies in about 10 days each year. The average survival rate reaches more than 80%.

5. Establishing Variety Records

Tree peonies are a flower and tree with many varieties, and the slightest negligence can cause variety confusion. Whenever the grafting propagation season comes, the farm designates technical experts who are especially skilled at identifying tree peony varieties to uniformly collect and cut scions and hand them over to grafting groups for grafting. During planting, variety records are tracked. After grafting is completed, a variety distribution map is uniformly drawn and stored in the records for future reference. In this way, when checking the survival rate, transplanting, or selling, everything can be seen at a glance.

6. Stumping and Pruning

Tree peony grafting is usually one rootstock to one bud (scion). After survival in the second year, if stumping is not carried out in the autumn of that year, the scion will only grow taller and not produce branches. Therefore, for grafted seedlings that have survived for one year, pruning should be done above the graft union (those exceeding 3 cm in length can still be used as scions for grafting again), in order to stimulate adventitious buds at the root bud area to sprout branches. In this way, 2-year-old grafted tree peony seedlings can grow 2-4 short branches. Usually, 2-year-old grafted tree peony seedlings can be transplanted at a plant and row spacing of 60×70 cm to cultivate large seedlings. To make grafted seedlings rapidly become large seedlings, stumping should be carried out immediately after transplanting that year (the cut short branches can still be used for grafting), in order to stimulate the production of more new branches. In this way, carrying out stumping and pruning for two consecutive years and strengthening fertilizer and water management not only enables grafted seedlings to rapidly reach the specifications for leaving the nursery, but also collects a large number of scions, which plays an important role in the rapid propagation of tree peonies.

The production practice of the Mangshan Flower and Seedling Farm in Luoyang has proved that no matter which tree peony variety series it is, counting from the day of grafting, after 4 years of cultivation, it can grow into a large seedling with 7-9 flower buds and reach the specifications for leaving the nursery. It achieves low cost, large quantity, and fast nursery release, and is a rapid propagation method for tree peonies worth promoting.