Old Red Cabbage

Last year I had kept some spare red cabbage seedlings in 3" pots - the idea being if any died / got eaten early I would use these as substitutes so I wouldn't have a space in Cabbage bed at the allotment. Some of these have survived in one of my cold frames - they have only grown to the limit of the 3"pots so are only about 3" tall -  - my question is .. Can I plant these year old substitutes this year or will it be a complete waste of time ?

I think you're correct - thanks MOS - might plant one out of curiosity...