Collected by Jerome Ostentowski of Central Rocky Mountain Permaculture in an alley in Alberta Canada, this Chenopodium has huge leaves with a succulent texture and excellent flavor for eating raw or cooked. It is a self-seeding annual that has been growing in his garden for fifteen years or more, so it is adapted for life in the forest garden.
Species uncertain, it apparently does not cross with the ordinary lamb's quarters in his garden. I'll be trying to find out what species it is, but ordinary Chenopodium album has many, many forms.
And compared to the ordinary lamb's quarters growing alongside: