I Have Healthy Plants With Huge Delicious Leaves But The Brussels Sprouts Are Not Growing Very Big. Why?

Question

7 1st year Brussels sprouts plants

Answer 1

There are two possible causes. One will be that temperatures are too warm. This will be a cool season crop, so any warm weather, at all, will be detrimental.

Another thing to consider will be fertilizer levels in the soil.

You may have to test and fertilize, accordingly.

https://www.gardeningknowhow.com/edible/vegetables/brussels-sprouts/brussel-sprouts-produce-loose-leafed-poorly-formed-heads.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm