Detailed Guide to Seedling Raising Methods and Cultivation Techniques for Catharanthus roseus
Growth Habits of Catharanthus roseus
Catharanthus roseus is native to the Mediterranean coast, India, and tropical America. Its cultivation history in China is not long, and it is mainly grown in areas south of the Yangtze River; cultivation is relatively common in Guangdong, Guangxi, Yunnan and other provinces (autonomous regions), where it is used for potted plants and planter boxes. It likes high temperature and high humidity, tolerates partial shade, and is not tolerant of severe cold. The most suitable temperature is 20-33°C. It likes sunlight, is averse to wet conditions and afraid of waterlogging. It can be cultivated in general soils, but saline-alkali soil is unsuitable; sandy or humus-rich soil with good drainage and ventilation is best. Its flowering and fruiting periods last almost all year.
Cutting Propagation of Catharanthus roseus
Cuttings of Catharanthus roseus are mostly taken from April to July. When propagating by cuttings, choose tender shoots from robust, pest-free mature plants as cuttings; generally select tender shoots 10-12 cm long from the plant tips, and the cutting length should preferably be 5-7 cm. For the cutting medium, use a mixed medium of plain sand, vermiculite, and peat. Wrap a small ball of mud around the base of the cutting, insert it into a cold frame at room temperature 20-24°C, and roots will form after about 20 days. Once the cuttings have rooted and survived, they can be transplanted into pots. Because plants propagated by cuttings do not grow as well as seed-grown seedlings, this method is seldom used in cultivation.
Sowing and Seedling Raising of Catharanthus roseus
1. Seed collection time: The fruits of Catharanthus roseus mature at different times because of different flowering times, so seeds must be collected as they ripen. After the fruit ripens and its color turns black, the skin easily splits open and the seeds are lost, so seeds must be collected in time. When the fruit skin turns yellow and the black seeds inside can be faintly seen, it is time to harvest.
2. Sowing time: The suitable temperature for germination of Catharanthus roseus seeds is 20-25°C. It is usually sown and propagated from March to May, and is mostly grown as an annual. To make it flower earlier, seeds can be sown and raised in a greenhouse in early spring at 20°C, then moved outdoors for cultivation after the weather warms.
3. Seedbed preparation: For the Catharanthus roseus seedbed, choose a place with high, well-drained terrain facing south and receiving sunlight, and with good drainage. The medium is best prepared from peat + perlite at 3:1, or leaf mold can be used. Water thoroughly with 500-600 times diluted carbendazim solution, then after it dries slightly, loosen and level the soil, and make beds 1.2 m wide.
4. Sowing technique: Broadcast Catharanthus roseus seeds at about 1000 seeds/sq m. After sowing, cover with fine, thin sandy soil; do not let the seeds be directly exposed to light. Water thoroughly with a fine watering can, then cover with plastic film or straw curtains to keep the soil moist. Seedlings will emerge in 7-10 days. After emergence, remove the film or straw curtains and gradually increase light. The seedlings grow slowly at first, then grow faster as the temperature rises, so thinning should be done in time. To prevent damping-off in Catharanthus roseus, spray or water once a week with 800 times diluted chlorothalonil or thiophanate-methyl for 2-3 consecutive weeks.
Cultivation Methods for Catharanthus roseus
1. Soil: Catharanthus roseus prefers fertile, well-drained soil and tolerates poor soil, but must not be grown in alkaline soil. In compacted, poorly aerated clay soil, the plants grow poorly, the leaves turn yellow, and they do not bloom.
2. Sunlight: Catharanthus roseus is a light-loving plant. During the growing period it must have sufficient sunlight; then the leaves are dark green and glossy, and the flower colors are vivid. If it is grown in shade for a long time, the leaves turn yellow and fall off.
3. Temperature: Catharanthus roseus likes a warm, slightly dry, and sunny environment. The suitable growing temperature is 18-24°C from March to July, and 13-18°C from September to March of the following year. In winter, the temperature should not be lower than 10°C.
4. Watering: Catharanthus roseus is averse to wet conditions and afraid of waterlogging, so potted soil should not be watered too much; excessive moisture affects growth and development. Especially for plants overwintering indoors, watering should be strictly controlled, and it is better to keep them dry, otherwise they are very likely to suffer cold damage. In open-field cultivation, during heavy summer rain, pay attention to timely drainage to avoid waterlogging that causes the whole patch to die.
5. Fertilizing: When fertilizing Catharanthus roseus, once every ten days a compound fertilizer and a liquid fertilizer can be applied alternately. A layer of base fertilizer should also be spread at the bottom of the pot soil as much as possible to ensure the nutrient content of the pot soil.
6. Pests and diseases: The Catharanthus roseus plant itself is toxic, so it is relatively resistant to pests and diseases. The main diseases at the seedling stage include damping-off and gray mold, and in addition, fertilizer burn and pesticide damage at the seedling stage should be prevented. If these occur, immediately water thoroughly with clean water, strengthen ventilation, and reduce the damage.
7. Pruning: Catharanthus roseus is an herbaceous plant and is quite suitable for potted cultivation, but care should be taken not to let the plant grow too tall, which would affect indoor decoration and ornamental value. Therefore, after the plant survives in the pot, pinch the tips several times to promote more branching and more flowering, and after flowering, the faded flowers must be cut off.