Oxalis is a shamrock-like plant that is also commonly referred to as love plant and wood sorrel. This plant is easy to grow, can sometimes be considered a weed and is a popular perennial plant that shows up around St. Patrick’s Day. Growing Oxalis is actually pretty easy. Keeping it under control can often be a bit trickier for some varieties.
Oxalis is a large family of flowering plants in the sorrel family with close to 800 species. It is found in most areas of the world and is very common in Mexico, South Africa and Brazil. It is sometimes referred to as a false shamrock because of the shape of its leaves but is not a member of the shamrock family. The plant is as happy outdoors in your garden as it is inside, growing in a pot.
Characteristics of Oxalis
Type of Plant
Oxalis is grown from small bulbs. It is relatively a slow growing perennial which spreads easily in a garden bed.
Depending on the color of leaves, the flowers can be white, yellow, rose colored or pink. The flowers grow on top of bare stems and are quite dainty, and thin, like the leaves. The plant tends to bloom in late spring or early summer.
This plant really pops at the garden centers in early spring. The deep maroon (almost black) leaves of purple Oxalis stands out near other dark green foliage plants. The leaves of the plant can be green or purple but have a three leaf clover look which gives it the common name false shamrock. In Ireland, four species of Oxalis are associated with good luck. Some leaves have a speckled appearance to them.
The leaves of the purple shamrock – oxalis triangularis – have a habit of closing up at night. Although they can take sunlight, it is not uncommon for the leaves to wither and drop off in the middle of summer. It grows better in the spring months when it is cooler.
The leaves are poisonous to pets but have a bitter taste to them so poisoning is not too much of a problem since cats and dogs tend to avoid the plant.
Size and Growth Habit
Oxalis is a mounding plant and grows to about 12 inches tall and wide.
Tips for Growing Oxalis
Well draining soil that is slightly acidic soil is ideal. (Coffee grounds sprinkled nearby can help with the acidity of the soil.) Using lots of organic matter or compost before you plant the bulbs will be beneficial.
The plant will grow best if it gets a few hours of sunlight every day. Afternoon shade is ideal. I have some growing in a sunny spot and others in my shade garden, and those in the shady spot seems to flourish the best. The leaves of oxalis may wilt slightly in the afternoon sun but recover quickly as the cooler temps come later in the day.
Plants with the darker purple leaves do better in sunlight than those with the green leaves.
Watering and Fertilizer Needs
Oxalis likes a moist soil that drains well but does not like to be in a soggy spot. Bulbs will rot easily if the soil is too wet, so be careful of over watering. Don’t underwater though, especially in the middle of summer. Fertilize regularly during the growing season with a normal plant food at half strength.
Get more plants for free by dividing the clumps of bulbs below the soil. Most oxalis plants remain fairly compact and are unlikely to need division very often in the garden. The plants also self seed so once you have a few growing, they will spread. (This can be a problem if the garden beds do not have edging for some types.)
Some varieties of he plant are cold hardy in zones 6 and warmer. It depends on the variety though. Many varieties are frost tender and will not over winter, so they are treated as annuals. To overwinter them, dig the bulbs up and grow them as indoor plants for the winter months and then replant again in spring.
Growing Oxalis indoors
This perennial loves a shady outdoor spot but also takes to pots. Growing oxalis indoors means placing it in bright light in a room with cool temperatures if you can. (60-70 degrees.) The more light the plant has, the darker the foliage will be, but too much sunlight can cause the leaves to “bleach out.” Feed with a regular houseplant fertilizer during the growing months.
There are close to 800 types of oxalis, but most are not considered invasive weeds. The two most common types are Creeping wood sorrel and Bermuda buttercup.
Since the plant spreads under ground, be sure that the garden beds where you grow them have some sort of deep edging or trench edging to keep them contained. Management of weeds in a lawn is difficult. Laborious hand digging does the job, but this can take several seasons to get it all. Don’t try to pull it out. Even a small piece of the root will re-grow and form new plants.
A broad leaf plant herbicide is best to try and control it, or for a more organic method, try liquid chelated iron, which also works on other clover type weeds in a lawn.
Growing Oxalis outdoors in a shade garden or indoors as a house plant is very easy. If you plan to have guests over for St. Patrick’s day and looking for a way to decorate, be sure to include a pot or two of oxalis. The shamrock shaped leaves are the perfect St. Pat’s Decoration.
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