Q.why was my terrace grown cabbage bitter?
thank you, Heather! I live in NYC and I guess I could plant some now, but there are no seeds or seedlings for sale anywhere!
The cabbage plants I grew on my terrace looked gorgeous – abundant, dark green leaves, but only produced teeny, tiny “heads” of cabbage that were incredibly bitter. Any suggestions for next time? Ought I plant more for winter?

Certified GKH Gardening Expert
Bitter leaves are an indicator that the plant is under stress of some kind. Because they are in containers, I would hazard to guess that the roots were too warm, which stressed the plants and caused only small, bitter heads to grow.
If you live in an area where cabbage will grow over the winter, growing it in the winter will certainly help. If you cannot grow it over the winter, then during the growing season, try shading the plants and packing an insulator like straw around the container to keep it even and cool.