Detailed Guide to Seed Sowing and Propagation of Catharanthus roseus in Pots

  Catharanthus roseus has 750 seeds per gram, and the suitable germination temperature is 18-24°C. Spring sowing can be done in April, using a sowing tray filled with a mixed soil of sterilized leaf mold, culture soil and fine sand; germination occurs 14-21 days after sowing. After seedlings emerge, shade for 2-3 hours is needed at noon when light is strong and the temperature is high. When the seedlings are 5 cm tall and have 3 pairs of true leaves, they can be potted.

  1. Seed collection time:

  Because the fruit of Catharanthus roseus ripens at different times depending on when the flowers bloom, the seeds must be collected as they ripen. Once the fruit matures and turns black, the skin splits easily 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 through it, it is time to harvest.

  2. Sowing time:

  The suitable temperature for seed germination is 20-25°C. Propagation is usually by sowing from March to May, and it is mostly grown as an annual. To make it bloom earlier, sow seeds in a greenhouse in early spring for seedlings, provide a 20°C environment, and move them to open ground for cultivation when spring becomes warm.

  3. Seedbed preparation:

  Choose a place with high, well-drained terrain facing south and receiving sunlight. For the substrate, it is best to use peat + perlite mixed at a ratio of 3:1; leaf mold can also be used. Water thoroughly with a 500-600 times dilution of carbendazim solution, then after it dries slightly, loosen and level the soil to make a seedbed 1.2 m wide.

  4. Sowing technique:

  Sow by broadcasting, about 1000 seeds per square meter. After sowing, cover with a thin layer of sandy soil so that the seeds are not directly exposed to light, water thoroughly with a fine watering can, and cover with plastic film or straw matting to keep the soil moist; seedlings emerge in 7-10 days. After emergence, remove the film or straw matting and gradually increase light exposure. Seedlings grow slowly at first and faster after the temperature rises. Thin them in time. To prevent damping-off in Catharanthus roseus, spray or water with an 800 times dilution of chlorothalonil or thiophanate-methyl once a week for 2-3 consecutive weeks.