Oxalis Triangularis

Oxalis Triangularis in pot

The striking purple blooms stand out amongst green indoor plants and it’s also photophilic, which mean that the blooms open and close in response to light. At night the blooms fold down and during the day they will open up. Have a look at some of these time-lapse videos.

Some plants are hard to take care of (I’m thinking of a Fiddle leaf fig) but the Oxalis Triangularis is fairly low maintenance. Oxalis is a genus of the wood sorrel family and is well known for being an invasive weed in most gardens. However, there are some varieties of Oxalis that are perfectly well behaved and don’t spread all over the places, such as the Oxalis Triangularis. Oxalis is often referred to a purple shamrock or false shamrock. Its history can be traced back to St Patrick in Ireland, even though the plant originated in Brazil.

How to care for it:

Light: Keep your Oxalis Triangularis in a filtered bright to medium light but away from direct light. It grows well in morning light (i.e. East window). It is fairly hard to burn this plant since Oxalis grows outdoors, the glass in your windows will filter out a lot of the intensity of the light, however it will grow best when its away from direct sunlight. Take a look at some of the images at the bottom of this article for the lighting suggestions.

Water: Allow the soil to dry between watering, ensure the top 2cm of soil are dry before watering. The worst thing you can do with bulbs is overwater as it will rot the bulb. Expect to water about once every 2 weeks.

Soil: A well-drained potting mix works well. Use a standard Premium indoor potting mix. Oxalis will NOT grow well in overly wet soil but does like moist soil. Make sure your pot has a drainage hole.

Pot: Oxalis pots need to be deep, shallow pots will not work well. Avoid growing them in a pot with other plants as they can go dormant and their growth requirements are different. As the Oxalis tends to grow and bend towards the light, you should also rotate your pot every 2 weeks to ensure the foliage grows evenly.

Temperature: Standard indoor temperatures are fine. The ideal temperature is around 60-70°F(15-21°C). Temperatures above 75°F/24°C become problematic. At high temperature, the Oxalis will start to look ‘tired’ and may go into dormancy and drop all its leaves.

Fertiliser: I don’t find fertiliser necessary in new plants, but you could add every 2 months if the soil is older than a year. Premium potting mixes usually contain slow release fertiliser for at least 4 months worth.

Some interesting facts

Pests and disease

Rust: One of the most common diseases is rust, which appears in the lower half of the leaves. I encountered this on one of my plants. You can use some rust sulfur copper powder to stop the spores from multiplying but there is no way to reverse the damage. Best is to cut off the affected leaves and wait for regrowth.

Ringspot: This is caused by the ringspot virus which is due to the presence of aphids, also known as plant lice.

Characteristics: Oxalis came to the United States in the 1980s and its popularity continues to grow. Indoors. When the weather is warm and there is adequate moisture, the Oxalis blooms with small, pale bell like flowers. There are about 300 species of Oxalis, the green leaf variety that makes great indoor plants is the Oxalis Regnellii. Oxalis gets its name from the fact that its high in Oxalic acid due to its tangy taste.

Dormancy: Oxalis occasionally go dormant and this happens suddenly in summer (which is quite strange for plants as it’s the growing season), this usually happens ever 2-7 years, it may look like your Oxalis has died. Don’t panic! Simply stop watering and let the soil dry and put it in a dark corner. In about 2-4 weeks you will see a new leaf emerge and then you can start to water again and move it back into a sunny spot. They can also go dormant when temperatures exceed 80°F/27°C

Toxicity: Oxalis is classified as an edible plant, however its very bitter for humans. Oxalis is poisonous to pets if eaten. Watch out for kitties that chew on the leaves.