Bowiea volubilis defies most categories. It is not an onion — despite its common name — but a succulent perennial in the lily family, native to the arid regions of eastern and southern Africa where it survives seasonal drought by storing moisture in a large, scaly green bulb that sits above the soil surface like a patient observer of the garden. From that bulb emerge thin, twining stems that reach toward whatever support is available, bearing tiny green-white flowers in spring before retreating into dormancy.

As a houseplant, it occupies a specific and pleasurable niche: a conversation piece for a bright windowsill or conservatory shelf, something that prompts the question 'what on earth is that?' before anyone has noticed there are flowers. It needs gritty, sharply drained soil, partial sun to shade, and water only during the growing season. During dormancy, it wants almost nothing. Temperatures below 50 degrees Fahrenheit cause damage, so in all but the warmest gardens (zone 10) it stays indoors. The plant is toxic and not edible. Propagation by seed, division, or individual scales is possible, though it is the bulb itself — exposed, architectural, quietly strange — that gives this plant its enduring appeal.