Oxalis, commonly known as wood sorrel or shamrock, is a diverse and widespread genus encompassing hundreds of species, each with its own charm and utility in gardens and natural habitats. This genus belongs to the family Oxalidaceae, and its members are found across the globe, from the temperate forests of North America to the tropical rainforests of South America, and the arid regions of Africa. The adaptability of Oxalis to different climates and conditions has made it both a beloved garden plant and, in some cases, an invasive species in areas where it isn’t native.
Leaves are trifoliate, giving them a clover-like appearance, which explains why some species are referred to as “shamrocks”. However, the genus includes species with varying leaf shapes and sizes, from the heart-shaped leaves of Oxalis triangularis to the more traditional, clover-like leaves of Oxalis acetosella. The leaves often exhibit a unique behavior known as nyctinasty, where they fold up at night or in the absence of light, which adds an interactive element to their cultivation. The foliage can range in color from vibrant greens to deep purples, with some species showcasing variegation or distinct patterns.
Flowers vary widely in color, including yellows, pinks, reds, purples, and whites, often with intricate patterns or stripes in some species like Oxalis versicolor, known as the Candy Cane Oxalis. These flowers not only contribute to the aesthetic appeal of gardens but also attract pollinators like bees and butterflies, enhancing biodiversity. The blooming period can be quite extended for some species, providing color throughout much of the growing season.
Many species grow from bulbs or corms, which allows for easy propagation through division. They generally prefer well-draining soil, with preferences for sunlight ranging from full sun to dappled shade depending on the species. Some, like Oxalis triangularis, are popular as houseplants due to their striking appearance and low-maintenance needs, while others are suited for outdoor gardens where they can naturalize or serve as ground cover. However, gardeners must be cautious with certain species, such as Oxalis pes-caprae, due to their invasive potential, which can outcompete native flora if not managed.
Species of Oxalis
Oxalis acetosella (Common Wood Sorrel)
- Native: Northern Hemisphere, including Europe, Asia, and North America.
- Characteristics: Small, clover-like leaves with white or pale pink flowers. Prefers shade, ideal for woodland gardens.
- Cultivation: Thrives in acidic, well-draining soil under trees or in shaded areas.
Oxalis triangularis (Purple Shamrock)
- Native: Brazil.
- Characteristics: Known for its purple, triangular leaves that fold up at night. Flowers can be white or pink.
- Cultivation: Loves bright, indirect light and well-draining soil. Can be grown indoors or out in warmer climates.
Oxalis deppei (Iron Cross Oxalis)
- Native: Mexico.
- Characteristics: Dark green leaves with a distinctive burgundy blotch, resembling an iron cross. Small yellow flowers.
- Cultivation: Prefers full sun to partial shade, good for rock gardens or pots.
Oxalis corniculata (Creeping Wood Sorrel)
- Native: Cosmopolitan distribution but originally from the tropics.
- Characteristics: Often considered a weed, with yellow flowers and spreading habit. Leaves are green or purplish.
- Cultivation: Can be invasive; best for ground cover where controlled growth is possible.
Oxalis debilis (Pink Sorrel)
- Native: South America.
- Characteristics: Pink or white flowers, with large, heart-shaped leaves. Can spread via bulbs.
- Cultivation: Prefers sun but can handle some shade. Good for borders or as a lawn alternative.
Oxalis tetraphylla (‘Iron Cross’)
- Native: Mexico.
- Characteristics: Similar to O. deppei but with larger leaves and more vibrant flowers, often red or pink.
- Cultivation: Similar to O. deppei, likes sun or partial shade, excellent for containers.
Oxalis versicolor (Candy Cane Oxalis)
- Native: South Africa.
- Characteristics: Striking flowers with pink stripes on white petals, grows from bulbs.
- Cultivation: Needs well-drained soil and partial shade; can be grown in pots.
Oxalis stricta (Yellow Wood Sorrel)
- Native: North America, now widespread.
- Characteristics: Bright yellow flowers, adaptable to various light conditions, can be invasive.
- Cultivation: Suitable for ground cover in managed areas, likes well-draining soil.
Oxalis grandis (Great Wood Sorrel)
- Native: Eastern North America.
- Characteristics: One of the taller species with bright yellow flowers, can reach up to two feet.
- Cultivation: Prefers full to partial sun, good for the back of borders or naturalizing.
Oxalis oreophila
- Native: South America, particularly Brazil.
- Characteristics: Large, dark pink flowers and heart-shaped leaves, grows in moist areas.
- Cultivation: Needs consistently moist soil, ideal near water features or in shade gardens.
Oxalis magellanica (Magellanica Oxalis)
- Native: South America, including Chile and Argentina.
- Characteristics: Small pink or white flowers, prefers cooler climates, often alpine.
- Cultivation: Suited for rock gardens or cooler garden spots, likes well-drained soil.
Oxalis violacea (Violet Wood Sorrel)
- Native: Eastern and Central North America.
- Characteristics: Violet to lavender flowers, grows from bulbs, prefers woodland settings.
- Cultivation: Ideal for shaded, woodland gardens with well-drained soil.
Oxalis pes-caprae (Bermuda Buttercup)
- Native: South Africa.
- Characteristics: Bright yellow flowers, often considered invasive, spreads rapidly via bulbs.
- Cultivation: Can be used for mass planting but control spread, prefers sun.
Oxalis incarnata (Crimson Wood Sorrel)
- Native: South America.
- Characteristics: Beautiful crimson-red flowers, grows from bulbs.
- Cultivation: Prefers sunny locations with well-draining soil, good for flower beds.
Oxalis purpurea (Purple-Flowered Oxalis)
- Native: South Africa.
- Characteristics: Deep pink to purple flowers, grows from small bulbs.
- Cultivation: Likes full sun, can be used in rock gardens or containers.
Oxalis articulata (Pink Sorrel)
- Native: South America, particularly Argentina.
- Characteristics: Delicate pink flowers, grows from bulbs, can spread in lawns.
- Cultivation: Prefers sunny to partially shaded spots, good for borders or naturalizing where control is possible.
Cultivation Tips for Oxalis
- Soil: Most prefer well-draining soil; some species can handle a range of soil types.
- Light: Varies from full sun to shade depending on the species, but most enjoy at least some sunlight.
- Water: Generally, they need moderate watering but can tolerate some drought. Overwatering can lead to bulb rot.
- Propagation: Many species propagate through bulbs or corms, which can be divided or planted directly.
- Invasiveness: Be cautious with species like O. corniculata or O. pes-caprae as they might become invasive in ideal conditions.