Oxalis Plant Care – How to Grow Shamrock Plants – Growing Ornamental Oxalis

Oxalis plant care is generally easy but some varieties of the plant can be considered a weed. Even so, it is a popular perennial plant that often shows up around St. Patrick’s Day.

Another version (candy cane sorrel) is also commonly seen during the holidays as a Christmas plant, because of its candy cane striped blooms.

Oxalis has shamrock-shaped leaves and is also commonly referred to as love plant and wood sorrel.

Keep reading to find out how to grow and care for it.

What is oxalis?

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.

The plant 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.

While many varieties of oxalis are invasive, ornamental oxalis is not to be shunned. It can take pride of place in any garden bed.

St. Patrick's Day will soon be here. Why not grow a shamrock plant? Oxalis has shamrock shaped leaves and gorgeous flowers. Grow in indoors now and plant it outside in early spring. Get the growing tips on The Gardening Cook.… Share on X

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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.

Oxalis flowers

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.

Leaves of oxalis plants

The foliage of this plant really pops at the garden centers in early spring. The deep maroon (almost black) leaves of oxalis triangularis stands out near other dark green foliage plants.

The leaves of the plant can be green or purple and 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.

There are varieties with solidly colored leaves and also those that are variegated.

Oxalis plants are nycytinastic

One interesting aspect of oxalis plants is how their leaves react at night.

The leaves of the purple shamrock – oxalis triangularis – have a habit of closing up at night, a trait known as nyctinasty. This habit is caused by light and temperature variations at night.

Although oxalis can take some sunlight, it is not uncommon for the leaves to wither and drop off in the middle of summer. Plants in a slightly shady spot seem to do better.

It grows better in the spring months when the temperatures are cooler.

Toxicity of oxalis

The leaves are poisonous to pets but they 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 of shamrock plants

Oxalis is a mounding plant and grows to about 12 inches tall and wide. Some varieties spread quickly and others are fairly slow growing.

Some types of the green oxalis can be quite invasive, but the ornamental purple oxalis is easily contained.

Invasive oxalis

Oxalis pes-caprae, also known as “buttercup oxalis,” is an invasive variety from South Africa that was transplanted to California in the 1900s.

Oxalis plant care in your garden

Soil Requirements for 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.

Sunlight needs for shamrock plants

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 with less sunlight than those with the green leaves.

Watering and fertilizer needs of oxalis

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.

On the other hand, don’t underwater, especially in the middle of summer.

Fertilize regularly during the growing season with a normal plant food at half strength.

How to propagate oxalis

Get more plants for free by digging up and 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 plants growing, they will spread. (This can be a problem if the garden beds do not have edging and grow the more invasive types which will spread to your lawn.)

Cold hardiness for oxalis

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.

Check your plant label for hardiness details.

To overwinter oxalis, dig the bulbs up and grow them as indoor plants for the winter months and then replant again in the spring.

Growing oxalis indoors

Oxalis plant care indoors is as easy. Just be careful of water frequency and give it bright sunlight.

This perennial loves a shady outdoor spot but can also be grown as a houseplant. Growing oxalis indoors means placing it in bright light in a room with cool temperatures if you can. (60-70 degrees is ideal.)

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.

Uses for oxalis

Shamrock plants look lovely along the border of a walkway.

Outside, oxalis has long lasting flowers and pretty foliage in a semi shady garden spot. The foliage of purple oxalis triangularis adds a nice break from normal green garden foliage.

Indoors, Plant it in pots and display during the St. Patrick Day holidays. It also looks gives a lovely contrast in terrariums.

Where to buy ornamental oxalis

Check your local big box hardware store. They sometimes have ornamental oxalis for sale.

Another good place to find oxalis for sale is your local Farmer’s Market, especially as spring approaches. There are many places to purchase oxalis online.

• Buy oxalis bulbs on Amazon
• Find oxalis triangularis on Etsy
• Purchase iron cross oxalis at Harmony in the Garden

Controlling invasive oxalis

There are close to 800 types of oxalis, but most are not considered invasive weeds. The two most common invasive 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 oxalis out by hand.

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 ornamental oxalis.

The shamrock shaped leaves are the perfect St. Patrick’s Day decoration.

Pin these oxalis plant care tips for later

Would you like a reminder of these tips for growing ornamental oxalis? Just pin this photo to one of your gardening boards on Pinterest so that you can easily find it later.

Admin note: This post first appeared on the blog in January of 2018. I have updated the post to add more growing tips, all new photos, a printable project card and a video for you to enjoy.

Yield: 1 happy plant.

How to Grow Oxalis

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Oxalis is often grown outdoors in semi sunny locations, but you can also grow it as a houseplant. These care tips will help

Active Time 30 minutes

Total Time 30 minutes

Difficulty easy

Estimated Cost $10

Materials

• Oxalis bulbs
• Compost or other organic matter
• Well draining soil
• All purpose plant food

Tools

• Watering can

Instructions

1. Choose a semi sunny location.
2. Till the soil and add organic matter to enrich it. Be sure the soil is well draining.
3. Plant oxalis bulbs 3-4 inches apart.
4. Water well.
5. Fertilize once a month during the growing season with half strength all purpose plant food.
6. Propagate by dividing the clumps of bulbs.
7. Flowers appear in late spring to early summer.
8. Most varieties are cold hardy in zones 6 and above. In colder climates, dig up the bulbs to use as indoor plants.
9. The purple varieties of oxalis are not invasive. Be careful of some of the plain green ones which can take over a garden or lawn quickly.

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