What are the key technical points for greenhouse cultivation and management of roses?
Rose (scientific name: Rosa rugosa), native to China. It belongs to the order Rosales, family Rosaceae, a deciduous shrub with many prickly branches, odd-pinnate compound leaves, leaflets 5-9 in number, elliptical, with marginal prickles. Petals obovate, double to semi-double, flowers purple-red and white, fruiting period August-September, oblate. The rose is native to China. When the rose is used as a crop, its flowers are mainly used for food and for extracting rose essence oil, and rose oil is used in cosmetics, food, fine chemicals and other industries.
The rose is a deciduous small shrub of the genus Rosa in the family Rosaceae, with brilliant flower colors; when cut while the buds are about to open and placed in a vase in water, its posture is very elegant and beautiful. Greenhouse cultivation of roses has very good market prospects.
1. Selection of site conditions. Roses have strong adaptability, like sunlight, and can also tolerate semi-shade; the suitable growth temperature is 15-25°C. The field for greenhouse cultivation should be selected as slightly acidic field with sufficient sunlight, high and dry terrain, deep soil layer, loose and fertile soil, and good granular structure. Roses planted in shaded and cold-waterlogged fields grow poorly, with thin and weak branches and leaves, very few flower buds, and small flowers with faint fragrance; if the site is low-lying, with a high groundwater table, plus poor drainage, it often causes root rot, leaf drop, and even death in patches. Although roses are not strict about soil nutrients, when planted in places with shallow soil, poor fertility, and soil prone to hardening, root development is hindered, branches and leaves are thin and yellow, and flowers are few and faint in fragrance.
2. Land preparation and acid adjustment. Land preparation includes plowing, ground clearing, leveling with harrow and rake, and removal of weeds and debris. Land preparation is carried out in autumn; the soil pH value should be 5.5-6.5, and hardened and heavy clay soil should be avoided. If the soil is too acidic or too alkaline, acid adjustment is needed; in production, 2 parts red soil plus 1 part leaf mold (peat soil can also be used) is mixed to adjust the pH. Before transplanting, the land needs to be prepared into beds; to facilitate fertilizing and weeding, the bed surface for planting rose flowers is 1.2 m wide, and it is best to open beds in a north-south direction for planting.
3. Selection of good varieties. Good varieties are an important foundation for commercial rose production; suitable varieties with high quality, high yield and high efficiency are the goal of good rose production. Double-petaled purple-red rose is currently the main cultivated variety of roses in China, and each place can choose suitable varieties according to local conditions.
4. Seedling propagation. Roses mainly use asexual propagation such as cuttings, layering and grafting to cultivate seedlings. Rose cuttings are best raised in nutrient bags in a greenhouse, and the survival rate is higher if a misting device is used. The cutting substrate is leaf mold or peat soil plus river sand plus superphosphate, mixed in a ratio of 5:3:0.5 before use; the sandy soil must be sterile. Put the substrate into cutting bags and arrange them in sequence in the cutting shed for later use.
The cuttings should be one-year-old disease-free and pest-free branches; softwood branches with buds before flowering or fully developed hardwood branches with flowers after flowering are suitable, with softwood cuttings best in May-August and hardwood cuttings best in September-October. The upper end of the cutting is cut flat 1 cm from the axillary bud, with 2-3 leaf buds left in the middle, and the lower end is cut into a 45-degree slant 1 cm from the leaf bud; the cutting length is 10-12 cm. The cuttings should be used as soon as they are cut, and rooting powder is used at the same time to accelerate rooting. Insert them into nutrient bags, with the insertion depth being 1/3 of the cutting, then water thoroughly once. After that, keep the air humidity above 90% and the shed temperature at about 25°C; after 30 days they can take root and sprout. After the rose cuttings survive, spray 0.2% urea and monopotassium phosphate 1-2 times in combination with watering. Thirty days before transplanting, choose a sunny noon to remove the film for hardening the seedlings.
5. Planting. Cutting seedlings raised in nutrient bags are very convenient to transplant. After the field bed surface is prepared in early March, open ditches in a north-south direction, with ditch depth 30 cm and width 20 cm, peel off the outer nutrient film and transplant with soil. The plant and row spacing for rose planting is preferably 20 cm × 30-40 cm. Before planting, apply decomposed fine farm manure as base fertilizer in the planting ditch, about 10 cm thick, cover with a layer of soil after fertilizing, place the plant in the center, fill soil around it and press firmly, and water thoroughly.
6. Environmental management. The optimum temperature during the rose growing period is 20-35°C during the day and 12-15°C at night. When the shed temperature exceeds 30°C in summer, growth is inhibited, flower buds no longer differentiate, and prolonged high temperature will kill the seedlings; when the shed temperature is too low in winter (below 15°C), it enters the dormant period and stops growing. Therefore, attention should be paid to heat preservation measures for roses to avoid damage that affects growth.
Roses are drought-tolerant but afraid of waterlogging. If water accumulates for a slightly longer time, the lower leaves turn yellow and fall, and in severe cases the plant will die. Therefore, do not plant roses in low-lying and damp fields to prevent waterlogging.
The principle of topdressing is mainly organic fertilizer, combined with phosphorus and potassium, and applied frequently in small amounts. The topdressing times focus on applying sprouting fertilizer at the early spring germination stage, flower-promoting fertilizer at the bud stage in May, and full-bloom fertilizer at the flowering stage, with an interval of about 10 days, applying once per mu 20-25 kg of clear manure water plus compound fertilizer. After harvesting cut flowers, open ditches around the plants and fill them with decomposed organic farm manure; after winter begins, water thoroughly, and at the same time prune dead branches, diseased branches and crossing branches. Fertilization should be timely; the rose growth period requires a large amount of organic fertilizer because the rose repeats the process of sprouting branches, growing buds, flowering and growing and developing about every 45 days. Therefore, the amount of nutrients consumed is very large, and various nutrients need to be supplied continuously to ensure the normal repetition of this process. During the vigorous growth period, fertilize usually once a week, and at the bud and flowering stage apply an additional quick-acting phosphate fertilizer and potassium fertilizer.
7. Pruning techniques. Pruning is an important part of rose production management. Because roses bloom on new branches grown in the current year, to keep rose plants growing vigorously and to produce more and better flowers regularly, continuous pruning is needed to remove some old branches and promote new shoots. Rose pruning is divided into flowering-period pruning and dormant-period pruning. Flowering-period pruning should be combined with cut flower harvesting, that is, after the first batch of flowers blooms, cut back 10-15 cm above the base of the flowering branch, and the second flowering will then have more and better-quality flowers. Dormant-period pruning is done before germination in early spring, leaving 4-5 branches per plant, cutting back 40-50 cm from the ground, leaving 1-2 side branches per branch, and cutting back each side branch leaving two buds, taking care to remove dead branches and diseased branches.