Moss Rose (Portulaca grandiflora)

Moss Rose, Portulaca, Purslane, Rose Moss, Sun Plant

Portulaca plants – Portulaca grandiflora, are a versatile, hardy, and colorful choice for gardeners in various climates. With their drought-resistant nature and stunning array of flower colors, they make excellent ground cover and can thrive in flowerbeds, containers, or hanging baskets.

I. Appearance and Characteristics 

Portulaca grandiflora is a succulent flowering plant in the purslane family Portulacaceae, native to southern Brazil, Argentina, and Uruguay and often cultivated in gardens. It has many common names, including rose moss, eleven o’clock, Mexican rose, moss rose, sun rose, table rose, rock rose, and moss-rose purslane. Despite these names and the superficial resemblance of some cultivars’ flowers to roses, it is not a true rose, nor even a part of the rose family or rosid group; rather, it is much more closely related to carnations and cacti.

It is also seen in South Asia and widely spread in most of the cities with old 18th- and 19th-century architecture in the Balkans.

It is a small, but fast-growing annual plant growing to 30 cm tall, though usually less. However, if it is cultivated properly, it can easily reach this height. The leaves are thick and fleshy, up to 2.5 cm long, arranged alternately or in small clusters. The flowers are 2.5–3 cm diameter with five petals, variably red, orange, pink, white, and yellow. Their upright, or ascending, long shoots branch usually near the base. The spreading 20-to-25-millimeters-long and 2-to-3-millimeters-wide leaves are almost or completely stalk-shaped, and taper towards the tip.

The axillary leaves have few to numerous whitish, woolly hairs which are usually shorter than the sheets. The compressed inflorescences are surrounded by eight to ten leaves. The large flowers reach a diameter of up to 4 centimetres. The five bright magenta-coloured petals are obovate and 15 to 26 millimeters long. Around the ovary with four to nine whitish scars are about 50 stamens. Capsules and seeds are not visible.

P. grandiflora is one of the few plants that is a C4/CAM intermediate, utilizing both C4 carbon fixation and Crassulacean acid metabolism pathways in different cells for photosynthesis.

II. How to Grow and Care

Sunlight

Moss rose plants need full sun, at least six to eight hours on most days to look and bloom their best. If you try to grow them in a shady area, they will fail to produce flowers and the flowers they do have likely won’t open.

Temperature and Humidity

A native of Brazil, Uruguay, and Argentina, moss roses like high heat and low humidity. It will tolerate cool, moist spring weather as long as it is frost-free. However, the best growth (and blooming) won’t occur until the summer heat comes along. Moss roses are frost tender and will die back come winter, likely at the first deep freeze (if not earlier).

Watering

Moss rose plants have low moisture needs, though they aren’t quite as drought-tolerant as cacti. The plants will tolerate periods of dryness, but flowering is usually better with some (well-drained) soil moisture. Plan to water the plant if you have a long stretch without rainfall—as a general rule of thumb, one deep watering per week during the hot summer weather should suffice.

Soil

These plants thrive in sandy and rocky soil and demand excellent drainage. If your garden bed has clay soil, grow your moss rose in containers rather than try to improve the clay soil drainage. Soil that retains too much water can easily cause the plant to die.

Fertilizing

Minimal fertilizer is needed for Portulaca, as it typically withstands neglect. An all-purpose fertilizer can be applied mid-summer to encourage new growth.

Pruning

At the most, moss roses need light pruning, and only if you live in a zone where they can survive year-round. The best time for pruning moss roses is in the early spring before new growth begins to emerge. Remove any growth that looks dead or diseased—you can also thin out a dense plant to improve air circulation, which can reduce the risk of fungal disease. Deadheading the plant’s spent blooms is not necessary.

Propagation

Like most succulent plants, moss roses can be easily propagated through cuttings. In fact, the cuttings will root readily and most gardeners find great success with propagation methods. Here’s how:

  • Using sharp, clean shears, make a cutting from a mature, established “mother” plant that has bloomed for at least one season. The cutting should be at least 4 inches in length and include at least one node.
  • Remove all leaves and flowers from the cutting.
  • Place the cutting in a small bowl of water as you prepare the rest of your materials.
  • In a small pot, combine a moist but well-drained mixture of sand, soil, and peat moss.
  • Bury the stem cut-side down at least three inches deep into the soil.
  • Cover the pot with a plastic bag or some other means of trapping humidity.
  • Move the cutting to a spot that gets bright filtered light and maintains a temperature between 65 and 75 degrees Fahrenheit. Water occasionally, just until the soil is moist. Cuttings should root within about two weeks, at which point they can be cared for as typical moss roses.

How to Grow from Seed 

Outdoors, seeds can be started in the landscape after the last frost. Press into moist soil and keep lightly moist until growth is visible. Sow seeds inside in a sterile seed-starting mix inside 6 -8 weeks before the last frost. Moisten the soil and press gently into the soil. Seeds do not need to be covered with soil.  Keep moist and place where seedlings will get bright light. After the danger of frost has passed, transplant it into a larger container or directly into the garden.

Overwintering 

Portulaca are annuals, growing, flowering and setting seed in only one growing season. They are not overwintered; simply plant new ones the following spring.

Pests and Diseases

Common Pests and Diseases

There are no pests or diseases specifically known to trouble Portulaca. In poor conditions, the plant can be subject to common pests like thrips, aphids, mealybugs, or spider mites. You can spray water on the plant to dislodge pests or spray with insecticidal soap.  

Overwatering or poorly drained soil can lead to root rot, powdery mildew, or a gray mold called botrytis. Portulaca is susceptible to these or other fungal issues if conditions are too moist or they are planted in areas with poor air circulation. Diseased sections should be removed and disposed of. Water early in the day to allow soil to dry out before cooler evening temperatures.

Common Problems 

There are no known issues specific to Portulaca. In hot summers, be aware that small animals like birds, squirrels or chipmunks may seek out Portulaca to eat because it retains water in its leaves. It is toxic to dogs, cats, and horses and can lead to kidney failure and death.

III. How to Get Moss Rose to Bloom

If you’re struggling to get your moss roses to bloom (or they’re not producing bountiful enough blooms for your liking), the problem almost always lies in the soil’s moisture level. Moss roses really dislike wet or soggy soil, and being planted in a medium that retains too much moisture will cause them to cease blooming. Try stepping back your watering cadence—you can also repot your moss roses into a container, which naturally drains faster than the ground would. Additionally, clay or terracotta pots can help wick excess moisture from the soil.

Another hugely important factor when it comes to having your moss rose bloom is ensuring it gets the proper amount of sunlight. Moss roses like ample light and hot conditions, and even an hour or two of shade can make the difference between bountiful blooms and barely any buds. Make sure your moss roses get at least six to eight hours of direct sunlight daily. If growing in a garden with other plants, you may even need to trim back nearby specimens so they don’t block the light.

IVCommon Varieties Portulaca Plants

There are dozens of varieties of portulaca available. The flowers come in plenty of colors, providing the gardener with plenty of variety in their landscaping requirements. The moss rose also makes for an excellent companion plant in flowerbeds, and it’s a great ground cover option as well.

These plants are an excellent choice for gardens throughout southwestern California, and the southern states. They do well in dry and rainy climates, as long as they get enough sun. Use the portulaca to fill in the gaps around your flowerbeds and pathways in the garden.

Some of the more popular varieties of the moss rose, or portulaca include the following

  • The Duet series – Produces beautiful bi-color flowers in red and yellow or rose and yellow
  • The Afternoon Delight – Keeps its blooms open into the early evening hours.
  • The Margarita series – An All-American selections winner
  • The Happy Hour – Early blooming and suitable for regions with fewer sunlight hours
  • The Sundance – Produces large flowers, on upright stems that are uncommon to any other variety

V. Uses and Benefits 

Numerous cultivars have been selected for double flowers with additional petals, and for variation in flower color, plain or variegated. It is widely grown in temperate climates as an ornamental plant for annual bedding or as a container plant.

Moss Rose (Portulaca grandiflora) Details

Common name Moss Rose, Portulaca, Purslane, Rose Moss, Sun Plant
Botanical name Portulaca grandiflora
Plant type Annual
Height 0 ft. 3 in. - 0 ft. 8 in.
Width 0 ft. 3 in. - 0 ft. 8 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Gold/Yellow
Leaf color Green