Around the second week of February, they appear on the impulse-buy racks near the checkout: a single heart-shaped leaf, fat and waxy as a poker chip, potted in a thimble of soil and wrapped in pink cellophane. The tag calls it a sweetheart plant. It costs four dollars. It will, in most cases, sit on a windowsill for somewhere between eight months and three years, never producing another leaf, never vining, never doing anything except slowly and stubbornly refusing to die — which is the only honest thing about it.
The leaf belongs to Hoya kerrii, a species native to Southeast Asia, from Thailand and Laos down through peninsular Malaysia. Kerrii is a legitimate and rewarding Hoya, capable of producing vines three meters long, clusters of pale yellow flowers with a burgundy corona, and, yes, those improbable heart-shaped leaves in pairs all the way up the stem. The Valentine's version, though, is not that plant. It is a single leaf-cutting taken without a node — a botanical dead end dressed up in seasonal marketing. Understanding why requires knowing something about how Hoya actually grows.