Why have my plants not formed sprouts on the stalks? They only have a cluster at the top, and are about 18 inches tall.
Certified GKH Gardening Expert
They don't develop heads for the same reason they bolt, which is normally heat. In addition, there may be too much nitrogen in the soil, which is focusing more leafy growth. Adding additional phosphorus (like bone meal) may help offset this and aid in head development. This article may also help: https://www.gardeningknowhow.com/edible/vegetables/brussels-sprouts/brussel-sprouts-produce-loose-leafed-poorly-formed-heads.htm