What else can I squeeze in with these eggplants. They are each in a 17 gallon steel bucket.
How about some strawberries around the edge? I heard the everbearing type can produce throughout summer and fall. I hope it's true because I have one growing vigorously without any flower buds yet.
I usually grow two eggplants in a 20-gallon container and the roots fill the container by season end, so I would guess your single egg plant will grow very well in that pot. It might depend on how big the eggplants you are growing will get. Some Asian and dwarf eggplants are pretty small, while black beauty and similar eggplants are fairly large.
You might try growing some herbs that attract beneficial insects, like basil or dill. Or some French marigolds, that are reputed to repel some bad insects. But my experience is that egg plant leaves get very big and will shade any plants growing under them. So sun lovers will be unhappy. I love the idea of mixing different plants in a vegetable container, but it has never worked well for me.
I normally grow my eggplant in raised beds with generous spacing and get great yeilds. This is a first for containers with them. I may just leave then all alone and just provide some mulch instead of nutrient robbing companions...
I'm no expert but I think that something fast growing with a shallow root system would be fine, like radishes. They would mature early. Also onions or leeks or whatever those smaller onion-type veggies are called. Lots of choices.