My zucchini female blossoms will not open. I check them at all hours of morning. The male blossoms open just fine. I have tried coffee grounds and eggshells (tea). I have also put the grounds and eggshells around plants. This makes the male blossoms bloom even more, but the squash get about 4 inches long. The blossoms won't open and the fruit shrivels and rots. They are planted in a waist high planter that is screened to keep out insects. What may be causing this? No insecticdes are used.
Female Squash Blossom
Certified GKH Gardening Expert
The humidity may be the cause of this. You can gently tear the female blossoms open (when they look to be a size they should open) and hand pollinate them. This article will help with hand pollinating them: