At one time it was grown in Britain on an industrial scale for starch production, not only to stiffen cuffs and collars and (earlier) Elizabethan ruffs, but it's also very similar to Cassava flour for culinary uses. In which case it might very well make a good flour paste for resist printing before indigo dyeing.
Countrylovers website tells you how to prepare the flour from the root - experiment at your own risk!
It has quite a strange smell and these colours...
...from my seasonal colour sample notebook.