Corgette/Pumpkin emergencies
 

Hello!

I live in Japan and desperately miss my courgettes. So, I planted some in my rooftop garden. They've been growing like weeds here, as well as some volunteer pumpkins from the compost we added. They just started flowering, but every flower opens for just a few hours before falling off, leaving no fruit anywhere! What's happening? I thought maybe they're not getting pollinated, but many of the flowers are falling off even before they open.

Help! I need my courgettes!

Cheers,
Olivia