Empty heart vegetable, Ipomoea aquatica, 空心菜,

I sowed three different Taiwanese vegetables in my garden. One had big seeds. It started to grow, but died soon. I wondered why, since other two seemed to grow reasonably, although slowly, since the month of May was very cold in Central Europe (Finland was basking in hot weather all the time). When I learned more about this plant, I understood why it died. Second sowing gave better results since the weather has been hot and sunny.