I seeded some Kale today in the space I had left in the onion container. The Spanish onions I planted in that container are doing well. A couple have stopped growing and don't look like they'll get any bigger. But the others are doing well and expanding their bulbs. We've had a few days of really strong wind so I positioned some sticks in the container to prop up the tops of some of the onions. A couple of leaves bending over is ok, but I don't want the tops to fold over entirely. Not yet anyway.
In that container I also planted a single leek. Most of the leeks I transplanted I'm growing in a bucket. But for some reason I decided to try growing just one plant in the onion container. It gets more sun than the others. I believe it was one of the weaker leek transplants I planted and after a month of thinking it wasn't growing it now appears to be doing quite well.