They do look like wasp nests, don't they? That's strange. I haven't seen any wasps flying around. I wonder if they abandoned it? I've never heard of a wasp making a nest on a plant. They don't look open either.

I would suspect they are not "nests", but egg receptacles. Insect probably laid eggs inside, then sealed the entrance and has gone on about her business. Eggs will hatch, break through the plug at the entrance and depart, leaving an empty chamber.

Bill

I was hoping to uproot the eggplant since it is no longer producing and I want to begin planting for the fall. But I don't want to hurt the nests. I'm having trouble finding information on how long it takes for the larva to emerge as an adult wasp. I'm also wondering if I could transfer the leaf with the nests to a ventilated jar and then release the wasps once they've "hatched."

You could just yank the plants and set them aside, somewhere out of the way. These types of wasps are pretty secretive, they tend to crawl around on plants hunting for things to eat (most eat caterpillars, which is why they are good to keep around). They are the type that fly around up where we would see them. They look like any other paper nest building wasp only they are usually much smaller. The nest just need to be kept out of the rain, which is why they are on the underside of the leaf. They should hatch soon and wander off.

One actually hatched. I just checked an hour ago and it's all busted open on one side.