Detailed Guide to Modern Rose Cut Flower Cultivation Techniques

Roses are shrub plants of the Rosaceae family. Along with chrysanthemums, carnations, and gladioli, they are known as the world's four major fresh cut flowers, and they are one of the best-selling fresh cut flowers on the market. Modern roses have rich colors, diverse flower forms, intense fragrance, and bloom year-round, making them deeply loved by people.

1. Varieties

Currently, there are 16 common modern rose varieties.

Red series: Cardinal, Red Success, Samantha, Marina, etc.;

Peach series: Miss Donna, Leading Lady, Sonia, Flamingo, Bellamy, etc.;

Yellow series: Gold Emblem, Gold Medal, Golden Times, etc.;

White series: White Success, Athena, Tineke, etc.;

Other series: Camping.

Because the market demands mostly red roses, during cultivation the quantity ratio of red to yellow and other color series varieties is usually 3:1:1.

2. Requirements for Environmental Conditions

Roses prefer a sunny, wind-sheltered, well-ventilated environment. They need at least 5-8 hours of direct sunlight per day to grow well. The optimal temperature is 18-25°C during the day and 15.5-16.5°C at night. Although they can survive at high temperatures above 35°C, they are prone to disease. The most suitable relative humidity for growth is 75%-80%. If the relative humidity is too high, they are prone to black spot and powdery mildew. The soil should be loam with good drainage, aeration, and granular structure, with a pH of 6-7.

3. Propagation and Cultivation

(1) Propagation: Cut flower roses generally use cutting and grafting propagation methods.

① Cutting propagation: For softwood cuttings, in June-July cut semi-mature branches after flowering, with every 3 buds as one segment; for flowering branch cuttings, in September-October cut mature branches, with every 3-4 buds as one segment. Keep the top 2 small leaves of the cutting, quickly dip the base in 400 mg/kg indolebutyric acid (IBA), insert to a depth of 2 cm, and after insertion cover with a small plastic arch shed to retain moisture. In the greenhouse, use straw curtains or shade nets for shading. Maintain a bed temperature of about 20°C and an air temperature of about 15°C. About 25 days after insertion, gradually remove the shade depending on rooting, and moderately increase ventilation. About 35 days after insertion, the small arch shed can be removed.

② Grafting propagation: Rootstocks are mostly cuttings or seedlings of wild roses. Bud grafting is carried out in July-August. One day before grafting, take plump branches after flowering, about 30 cm long, keep the petioles and remove the leaves, cut off the prickles, and soak in water for later use. Generally, the "T"-shaped budding method is used, and the budding positions should face the same direction for easy inspection. Cleft grafting is carried out in February-March, mainly using cut grafting. Generally, when the rootstock is 9-13 mm thick and the scion is 3-8 mm, grafting can be performed.

(2) Cultivation:

① Soil: Requires soil with strong air permeability, good drainage, the ability to retain water and nutrients, and no pests or diseases. It can be prepared by mixing good loam with peat and sand in a volume ratio of 2:1:1. Use gypsum or lime to adjust the pH to 6-6.5, and disinfect and sterilize the prepared soil.

② Planting: Newly planted plants should be pruned, leaving 15 cm in height. In particular, broken and damaged roots and branches should be cut off, and the terminal bud must be plump. The planting depth depends on whether the surface is mulched. For example, leave the graft union 5 cm above the soil surface, and cover the soil surface with 8 cm of mulch material (such as leaf mold, sawdust, and other organic matter). Later, this 8 cm will gradually settle to 5 cm, exactly below the union. If no mulch is added, it can be planted deeper.

The row and plant spacing for cut flower roses is commonly 30 x 30 cm. During the period just after planting, spray several times a day to keep the aboveground branches and leaves moist.

③ Topdressing: During growth, roses need relatively balanced fertilizer. They should neither grow too slowly nor become leggy. Usually, the macroelements or trace elements required by roses are mixed into a compound fertilizer and applied.

④ Pruning and pinching: One pruning method is gradual replacement pruning, that is, after the first harvest and cut in spring, leave the whole plant about 60 cm high, allow part of it to bloom again, and shorten part of it. After the new shoots from the shortened part bloom, then shorten the part that previously bloomed, so that they bloom in turn and continue blooming throughout the year. Another method is one-time uniform pruning, that is, after the first harvest and cut in May, shorten all plants to the same height into a shrub form. If they are young plants newly planted in the first year, leave them 45 cm long; from the second year onward, leave them 60 cm. However, this pruning method causes basically no production for 5-6 weeks, after which cut flowers can be produced continuously until the following May, when they are cut back to the ground again.

Pinching of roses is done when new shoots grow to 15-20 cm, removing about 3 cm from the top, thereby promoting side buds to grow into side branches. When they reach a certain length, pinching should still be done 1-2 more times, until the number of main branches and side branches of the whole plant is sufficient to produce a large number of flowers. Pinching in the early stage is to adjust plant shape, but after flowering it is to control the flowering period. When the flower bud diameter reaches 10-13 mm, remove the branch tip down to the second leaf, which can promote flowering by about 7 days.

4. Harvesting, Cutting, and Preservation

Roses should be harvested and cut when the temperature is low and humidity is high. Generally, they are harvested and cut 1-2 days before flowering. The cut branches should have 5 internodes or a somewhat longer length. One hour after cutting, insert them into water to absorb water, then grade them by length, tie them in bundles of 10 stems, and package them in cellophane.

Rose cut flowers have a short preservation period and do not tolerate long-distance transportation. After harvesting and cutting, if roses are not put on the market @#@136@#@, they should immediately be stored in a low-temperature warehouse. The storage temperature is 1-2°C, and it is best to insert them in water for wet storage. The water quality for wet storage is very important; low pH is beneficial to rose cut flowers. The preservative in the holding container is a mixed solution composed of silver thiosulfate and aluminum sulfate.

Common formulas for rose vase preservatives include: ① 40 g/L sucrose + 80 mg/L 8-HQS (8-hydroxyquinoline salts) + 100 mg/L isoascorbic acid; ② 20-60 g/L sucrose + 250 mg/L 8-HQS + 500 mg/L citric acid + 25 mg/L silver nitrate; ③ 50 g/L sucrose + 200 mg/L 8-HQS + 50 mg/L silver acetate; ④ 20 g/L sucrose + 300 mg/L 8-HQS + 250 mg/L cobalt nitrate.