Grafting cucumber seedlings onto black-seed pumpkin rootstock is a widely practiced technique in overwintering cucumber cultivation. This method not only enhances the plant's resistance to diseases but also improves its ability to absorb nutrients and withstand cold temperatures. However, ensuring a high survival rate after grafting remains a crucial challenge for growers. Several factors influence whether grafted cucumbers will thrive, and farmers should pay close attention to the following key points.
First, selecting a rootstock with strong compatibility with cucumbers is essential. Black-seed pumpkins are commonly used due to their good grafting affinity. It's important to time the sowing correctly—cucumbers should be planted about five days earlier than the rootstock to ensure they are at a similar growth stage when grafting occurs.
Second, choose a grafting technique that you are familiar with. Common methods include cleft grafting and splice grafting. The ideal size for cucumber seedlings is 7 to 10 cm tall, with a heart length of 1 to 1.5 cm. The pumpkin’s cotyledons should be flattened, and the true leaves just starting to emerge. Grafting should take place in a greenhouse, where the temperature is maintained between 25°C and 28°C, and humidity stays above 95%. If temperatures rise too high, shading materials can be used to cool the environment.
Third, always keep your tools clean during the process to avoid infection at the graft site. Any contamination can lead to failure or disease.
Fourth, handle the seedlings carefully to avoid damaging them, which could result in tissue necrosis and poor recovery.
Fifth, maintaining proper environmental conditions is vital for successful healing. After grafting, the temperature should be kept between 25°C and 30°C during the day and 18°C to 20°C at night. Three days later, reduce the daytime temperature to 25°C–27°C and nighttime to 14°C–16°C. Once the roots start forming, increase the daytime temperature to 28°C–32°C and nighttime to 8°C–16°C for 3–5 days before transplanting. Finally, lower the temperature to 20°C–23°C during the day and 10°C–12°C at night.
After planting, avoid ventilation and maintain 100% humidity. If the temperature becomes too high, use shade nets to prevent overheating. After three days, gradually introduce ventilation, reducing humidity to 70%–80%. Over time, slowly adjust the temperature and acclimate the seedlings to normal conditions.
Lastly, it's important to wait until the graft has fully healed before cutting the rootstock. Premature removal can weaken the new plant and reduce its chances of survival.
By following these steps, farmers can significantly improve the success rate of their overwintering cucumber grafting, leading to healthier and more productive plants.
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