How do I grow Amaranthus? this year mine have all been stunted and shrivelled.

Your plants may have suffered from drought this year, so next year make sure the soil around them never dries out.

Start the seed off in a heated propagator in March (week 10), in small pots / tray, filled with  a good, proprietary seed compost.

As soon as the seedlings are large enough to be handled, prick them out individually into modules or boxes.

Grow them on in a light, frost free, sunny position. e.g a coldframe

Plant them outside in early June, in a sunny and sheltered site where the soil has been improved with well rotted organic matter .

Feed the plants at intervals with a high potash liquid fertiliser.