I've been interested in Chaya also. We have a native relative in this region but there aren't many of them around and as far as I know only the seeds are considered edible. If Chaya will grow under similar conditions it will be a good plant to have. How to obtain it seems to be a challenge.
Location: Currently in Lake Stevens, WA. Home in Spokane
posted 7 years ago
ECHOnet has been distributing this plant for a long time. Here is what they have to say about it:
“I would consider chaya to be one of the five most important underutilized
food plants ECHO distributes. I give it this rank because of its ability to
thrive in both arid and rainy regions, its little need for care or extra
fertility, its lack of insect or disease pests, its high production per
square foot, and the exceptional nutritional value of its cooked leaves.”
I happened upon this plant just this last week while thumbing through the J.L. Hudson Seedsman catalog. It is on my list of seeds to order later this fall. Also living in Zone 7b/8a I plan to give it a try this next season. They have it listed as Chenopodium Giganteum or "Purple Goosefoot".
I read just now that Chaya does best in zones 9-11. You might be pushing it in zone 8. It doesn't sound like it will tolerate too much water either. Maybe it would work in a high raised bed (hugelkulture perhaps?) next to a south-facing wall.