Oxalidaceae
Oxalis
The wood sorrels — clover-like leaves that fold at night and in bright sun on a hinge at the base of each leaflet, the same kind of hydraulic pulvinus the prayer plants use, evolved separately. The genus is named for oxalic acid, which it does contain, and which the internet is much more frightened of than the numbers warrant.
Native to Cosmopolitan
How Oxalis generally wants to be treated
Species pages start from this and record only where they differ.
- Light
- Bright indirect to a little direct sun. The leaves fold in strong light, which is a normal response rather than a complaint.
- Water
- Evenly moist in growth, and less when growth slows. The important thing is knowing which kind you have — see dormancy.
- Humidity
- No figure is published for the genus. Ordinary room air suits the shrubby species.
- Temperature
- Ordinary room temperatures suit the tender species; many are frost-hardy outdoors.
- Substrate
- A free-draining potting mix.
- Fertilizer
- A balanced feed at half strength in growth. No extension source publishes a regime for the genus.
- Propagation
- Division, or cuttings for the shrubby species. Many species self-seed readily.
- Dormancy
- This is the field that matters, and it depends entirely on the species. The tuberous ones — the shamrocks people buy for St Patrick's Day — go genuinely dormant and want to be left dry until they come back. The shrubby ones have no storage organ to retreat into and no dormancy at all, so a collapsing plant is dying rather than resting. Kew's lifeform field distinguishes the two: tuberous geophyte against subshrub. Check yours before you withhold water.
- Common problems
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- Treating a shrubby species like a dormant tuberous one, which kills it — the single most consequential mistake in this genus
- Rot from a tuber left wet through its rest
- Leaves folding by day: normal, and a light response
- Spider mites and aphids in dry air
- Toxicity is badly overstated. NC State rates severity Low with no documented human cases, and the arithmetic behind a genuinely dangerous dose runs to something like a kilogram of leaves
In the collection
- Golden oxalis Oxalis vulcanicola Donn.Sm.