Ornamental · Portulacaceae
Moss Rose
Portulaca grandiflora
Give it scorching sun and dry, sandy soil, and moss rose blankets the ground in color all summer.
Full sun
Every 7–14 days
59–95°F · 15–35°C
USDA 2–11
Overview
Moss rose is the plant for the spot where nothing else will grow. It's a low, spreading succulent with needle-fine leaves and bright, ruffled flowers, and it thrives on heat, drought, and lean soil that would starve fussier annuals. Native to South America, it has become a favorite for rock gardens, edges, and containers that bake in the afternoon sun.
The flowers are the whole show. They come in hot pinks, oranges, reds, yellows, and whites, often as full doubles that look like tiny roses, which is where the common name comes from. There's a catch worth knowing up front: the blooms open only in bright sun and fold shut on cloudy days and in the afternoon, the trait behind its other name, the eleven o'clock plant.
Few annuals ask for less. Plant it in poor, fast-draining ground, give it all the sun you have, and water only when the soil dries out. Overdo the kindness with rich soil, heavy feeding, or frequent watering and you get soft, rot-prone stems and far fewer flowers.
Care
The short version: full, direct sun and dry, sandy, fast-draining soil. Water only once the ground has dried out, skip the heavy feeding, and let the heat do the rest.
Light
Moss rose wants full, direct sun, ideally 6 or more hours a day. The flowers only open in bright light and stay shut in shade, so the sunnier the spot, the more color you get.
Water
Treat it like the succulent it is and let the soil dry out completely between drinks, roughly every 7 to 14 days. Overwatering is the fastest way to kill it, and the plant shrugs off heat and drought far better than a soggy bed.
Soil
Plant it in sandy, fast-draining soil, even poor ground that other annuals would sulk in. A pH anywhere from 5.5 to 7.5 suits it, and sharp drainage matters far more than fertility.
Temperature
It revels in warmth and runs happily from 59°F to 95°F (15°C to 35°C). Frost ends it outright, so it only goes out once the cold has truly passed.
Humidity
Low humidity is exactly what it likes, so there's no number to chase. Dry air and good airflow keep the rot at bay that damp, still conditions invite.
Feeding
This plant barely needs feeding and flowers best when a touch hungry. Skip it altogether in lean soil, since excess nitrogen trades blooms for leaves, and a single light feed in summer is plenty in poorer ground.
Pruning
Pinch back any leggy stems to push the plant into bushier, fuller growth. You can skip deadheading entirely, because moss rose cleans itself and reseeds on its own.
Repotting
Grown as an annual, it rarely needs repotting. Just pot up nursery starts at transplant time, and watch for roots circling the pot or soil that dries out almost instantly as a sign it wants more room.
Size & spacing
Plants stay low, around 4 to 8 inches (10 to 20 cm) tall, and spread into a mat 6 to 12 inches (15 to 30 cm) wide. Space them so the mats knit together without crowding, which keeps air moving and rot down.
When to plant
Moss rose is a warm-season annual that waits on heat and won't take frost. Start seeds indoors in late winter, set plants out once the soil has warmed and the last frost is gone, and enjoy the blooms from summer into early fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6 to 8 weeks before the last spring frost
- Plant: After all danger of frost has passed and soil has warmed
- Harvest: Summer through early fall
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Almost every moss rose problem traces back to one of two things: too much water or too little sun. Read the early signs in the stems and the flowers, then adjust the conditions before damage spreads. Match what you see below and act while it still helps.
Soft, blackened stems collapsing at the base
This is root and stem rot, almost always caused by too much water or soil that won't drain. The stem base turns mushy and discolored while the ground around it stays wet for days. Cut back on watering, work some sand or grit into the bed to open it up, and pull any plant that has rotted through.
Fix:
- Reduce watering and allow soil to dry
- Improve drainage with sandy or gritty soil
- Remove and discard severely rotted plants
Plenty of leaves but barely any flowers
When the foliage looks lush but the blooms never come, the plant is usually short on direct sun or carrying too much nitrogen. Moss rose needs at least 6 hours of strong sun to open its flowers, and a heavy feed pushes leaves at the expense of color. Move it into the open and ease off the fertilizer.
Fix:
- Move to a full-sun location
- Stop or reduce fertilizing
Toxicity
Moss rose is mildly toxic, so it's worth keeping an eye on pets and grazing animals around it. The leaves and stems hold soluble calcium oxalates, which mostly cause drooling and an upset stomach, though a large mouthful can bring on weakness and strain the kidneys. Keep it away from cats, dogs, horses, and other animals, and treat its edible cousin purslane as a green for moderation.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Mild
A nibble usually just brings on drooling and a queasy stomach. A cat that eats a real mouthful can dribble heavily and turn weak, and a large dose puts the kidneys under strain.
Dogs Mild
Most dogs that chew a few stems get away with some drooling and an upset gut. Watch for weakness or off-and-on vomiting if a dog has grazed on a lot of it.
Horses Mild
A mouthful or two tends to pass with little more than slobbering and a dull stomach, but a horse that grazes heavily can grow weak as the oxalates build up and tie up calcium.
Rabbits Caution
The same soluble oxalates make moss rose a poor choice for rabbits. Keep it out of the hutch and the run rather than risk a sensitive gut.
Livestock Caution
Goats, sheep, and cattle rarely seek it out, yet a hungry animal on bare ground could browse enough to drool and weaken. Fence it off where stock graze.
Birds Caution
Pet and backyard birds can react to the oxalates too, so it's safest to keep the plant away from cages and runs.
People Caution
Garden moss rose is best left alone in the bed. Its close cousin purslane is eaten as a green, but it carries the same oxalates, so even that is for moderation rather than handfuls.
Common purslane (Portulaca oleracea) is eaten by people but also contains oxalates and should be consumed in moderation.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most garden moss rose comes from a few breeding series, each one selected for fuller flowers, bolder color, or staying open in less than perfect light. These are the ones worth knowing by name.
Sundial Series
A compact double-flowered hybrid that opens earlier in the day and holds its bloom longer in weaker light than most.
Margarita Series
A vigorous, heat-loving double bred to keep performing in beds and containers through the worst of summer.
Happy Hour Series
A mounding type that carries large double blooms across an unusually wide range of colors.
How to propagate
Moss rose is among the easiest annuals to multiply, whether you raise it from its dust-fine seed or root a few cuttings off a plant you already grow.
SeedEasy
Start indoors 6 to 8 weeks before last frost or direct sow after frost; self-sows readily · 2 to 4 weeks to germinate and establish
Moss rose grows easily from its tiny seeds, which need light to sprout, so press them onto the surface rather than burying them. Start a tray indoors 6 to 8 weeks before your last frost, or scatter seed straight into warm ground once the cold has passed. Give it 2 to 4 weeks to germinate and settle in, and expect it to self-sow freely from then on.
Stem cuttingsEasy
During the active summer growing season · 1 to 2 weeks to root
Cuttings root with almost no fuss during the active summer growth. Snap off a healthy stem, let the cut end dry and callus for a few hours so it won't rot, then push it into gritty soil. It takes hold in about 1 to 2 weeks.
Myths
Portulaca is completely safe for pets because purslane is an edible vegetable.
The two are related, but that doesn't make the garden plant a snack. ASPCA lists Portulaca species as toxic to cats, dogs, and horses because of soluble calcium oxalates, and even edible purslane carries those same oxalates. Keep it out of reach of pets.
Moss rose flowers stay open all day.
The blooms only open in bright, direct sun and shut again in shade, on cloudy days, and through the afternoon. That habit is exactly why it earned the name eleven o'clock plant.