North53, some of the seed I had sown was a good 5 or 6 years old, it had germinated and grown normally. When had you sown them? ... if started too early, then these will runt out and just sit all summer and do nothing, an unusually cool spring will also hamper them. Amaranthus can be directly sown as soon as the ground is workable, they will often self sow and these are generally the strongest most vigorous plants, next spring all my amaranthus varieties will be sown in the garden ... though, if you want to get a jump start within a shorter growing season, plant them about mid to late April and grow under cool bright and ventilated conditons (ventilation will help with dampening off) Plants can very quickly become spindly ... though, you can always bury the stems down deeper when planting out.

So, give them another try next spring, they really are very easy to grow! Do stay away from the tricolor types, the so called Summer Poinsettia kinds, these I've never had any success with.

Terry

I doubt that old seed is the issue. I've found they aren't really particular about part-sun and will just kinda sit there, not really growing much. I always plant mine in full sun but this year I had a few 6-cells left over so I put them here and there in some notfullsun spots and the result wasn't great. The rest of them in full sun were super. Velvet Curtains is a favourite of mine to use in bouquets - just smashing mixed with pretty much any colour, but I really, really love it with pink and a soft yellow.

Thanks Twrosz & Pudge.
I don't think location was the problem Pudge, as they were in pretty much full sun.
Now that I think about it we did have a late cold spring. I didn't think it was ever going to be warm enough to plant out the annuals. I also had a problem with my coleus which usually are very good performers for me. They were even worse than the amaranthus in that many of them just up and died. Those that lived never did fill out. I must have planted before the soil was warm enough. I should know better.
Anyway, it's good to know the seed wasn't the issue.