You may not need a phytosanitary certificate if this is intended to be a houseplant*, according to this post in Frustration with importing trees | UBC Botanical Garden Forums. You may want to do some followup research. * I take this to be the case as the question has been posted in the Indoor and Greenhouse Plants forum.
Peruvian Ground Apple, Yakon, Yacon - Smallanthus sonchifolius The plant will grow here in the PNW - a crisp, sweet tasting perennial tuber from the Andes, it is related to the sunflower and will grow to zone 7. You can either leave the tuber in the ground or dig and store for the winter before replanting in the spring. I'm hoping my little patch will multiple quickly
You may want to check with some of your larger garden centers.....I saw Garden Works here in BC selling the plants just two weeks ago for $10 a pot.
I would say that it is better to source from a reputable nursery or greenhouse that you know does not use toxic chemicals on the seed, systemic or aesthetic. Pretty much all of the big-brand garden stores that carry plants (including grocery stores) are selling plants that are harmful to pollinators and otherwise. Not worth buying.
