Apparently they like a shady spot and grow to 12" (30cms) tall when you can harvest them back to 2" (5cms) for soups or salads or anything you would do with spinach.
We planted them out small after hardening them off for a couple of weeks because we were running short of pots but they are very forgiving and you can still plant out when they are almost fully grown.
Beware though, don't let the delightful daisy-like flowers bloom as this will turn the edible stems and leaves bitter.
also be hypervigilent against slugs as they too find chop suey greens very tasty, we've used raw sheep's fleece to deter even the hungriest field slugs from trying it on.
Final update: Despite heavy losses due to slugs ignoring any advice against raw sheep wool. Which involved picking them off after dark! We managed to get the greens to grow big enough to harvest. Did this early this sunny morning to give them some recovery time before the munching monsters of the dark arrive back!