I have a dozen perennial hibiscus about 2 years old now. I got them from someone gave me some roots or starters.

Now my question:

The flowers are now begining to fall off and the place where the flower was now has a football shaped "nodule" about as big as my thumbs first knuckle. From what I am reading these nodules should turn brown and then open up. Mine are very green and not getting brown but they are opening and I can never find any seeds under the plants.

I have tied plastic bags around several of these nodules, and hopefully may catch some seeds when the nodule bursts. I have opened up some of the large ones still attached to the plants and there are about 6-10 little white balls which I assume is the seed.

Can anyone advise me as to why the nodules open with no warning. Thank you very much for any advice.