Oxalis hedysaroides / Oxalis hedysarifolia, Fire Fern

Have you ever seen a herbaceous, purple-leaved Oxalis that grows like a tiny tree?

Today I really have to talk about this plant.It’s one of my absolute favorite indoor plants.

If you often watch my videos or look at my photos, you may have noticed a purple plant that appears in the background all year round — spring, summer, autumn, winter — always there.That is not an artificial plant.It’s an Oxalis.

This herbaceous purple-leaf Oxalis —scientific name Oxalis hedysaroides / Oxalis hedysarifolia, commonly called Fire Fern — is not a fern at all despite its name. Instead, it’s a very unique wood-forming, purple-leaf Oxalis species.

Let me start with why I love it so much:

First, it’s a foliage plant, and as a foliage plant, it is perennial and does not drop leaves.

Second, its color doesn’t change with heat or seasons.When I say “doesn’t change,” I mean it won’t turn green in summer or high temperatures. It stays purple all year — sometimes deeper, sometimes lighter — but always purple. This is incredibly important. Many beautiful plants you see online — succulents, maples, etc. — only look good during a short, specific window when conditions are perfect.But not this one. Its appearance is consistently beautiful.

Third, it may be herbaceous, but it has slender, elegant branches and grows like a bonsai.

Fourth, it requires almost no care. I’ve never changed its pot since I bought it. It grew from just over 10 cm tall to its current size in the same pot.

With so many advantages, it’s truly an outstanding indoor plant.Now, let me introduce this special Oxalis properly.

Fire Fern (Oxalis hedysaroides / Oxalis hedysarifolia)

Fire Fern is an exceptionally ornamental, wood-forming Oxalis.Its leaves range from deep purple and wine-red to almost black, with clear veins and flame-shaped leaflets. From a distance, it looks like a miniature purple tree, which is why it’s so popular among plant lovers.

🌿 Botanical Profile

• Scientific name: Oxalis hedysaroides / Oxalis hedysarifolia

• Family: Oxalidaceae

• Type: Perennial herb, but the base and branches gradually become woody, forming a shrub-like structure

• Common names: Fire Fern, Purple Shamrock Tree

🌈 Appearance (What makes it so charming?)

🍃 1. Three-leaflet compound leaves, glowing like fire

• Each leaf has three leaflets

• Color changes with light:

  • Low light → deep purple-gray

  • Strong light → wine red or black-purple

• New leaves come with reddish bracts, like tiny flames emerging from the branch tips

🌳 2. Woody stems that grow into a “mini tree”

This is the most unique feature of Fire Fern:Very few Oxalis species grow into small shrubs.My plant has clearly grown into a little tree — absolutely beautiful!

Now, let’s look at its care. As usual, I’ll show you what online sources say, then add my own experience — and correct anything that’s inaccurate.

🌱 Care Tips

🌼 3. Yellow flowers that brighten the purple foliage

(The flowers are just an accent. Honestly, it looks even better without them — just my personal opinion.)

• Bright yellow, five-petaled flowers pop out from the purple leaves

• Not many, but the contrast is striking

☀ Light

(Works indoors or outdoors. Outdoors the color becomes brighter; indoors it’s a deeper purple. But either way — it’s always purple.)

• Prefers bright indirect light to half-day sun

• The stronger the light, the deeper and brighter the leaf color

• Indoors near a window is perfectly fine

💧 Water

(I keep mine on a north-facing balcony with begonias and ferns. I water all of them together. Daily watering is totally fine.)

• Keep slightly moist to lightly dry

• Does not like long-term waterlogging

• More drought-tolerant than common Oxalis varieties

🪴 Soil

(Whatever soil you use for general houseplants is fine — it’s not picky at all.)

• Loose, well-drained mix such as:

  • volcanic rock + peat + perlite

🌡 Temperature

(The usual information online isn’t completely accurate. In my location — a hot southern tropical city in China — I keep it outdoors, and even temperatures below 10°C in winter don’t bother it.)

• Ideal: 18–30°C

• Not frost-hardy (below 5°C it may drop leaves and go dormant)

You can also propagate this plant yourself.Just bend a branch down into a small pot, pin it with a stone, and after a few weeks it will root.I’ll upload the video soon.

(the following photos are taken in different time of a year, and even include some small plants I propagated).