Portulaca, the genus that includes moss rose and purslane, can live for years, but only where winters stay frost-free.1Proven Winners. Portulaca – The Ultimate Growing Guide from Proven Winners For most gardeners that makes it a one-summer plant, blooming until the first frost kills it. Even so, a plant that dies in fall can seem to return in spring, because its seeds survive what the plant cannot.
Where Portulaca Lives as a Perennial
Portulaca species can grow as annuals or perennials depending on climate.2PubMed Central. Resilience of Portulaca plants to environmental stresses and the economic potential of their bioactive compounds In warm areas like USDA zones 10–11 it can keep growing as a perennial.3PubMed Central. Resilience of Portulaca plants to environmental stresses and the economic potential of their bioactive compounds In colder regions the plant finishes its life before frost, because cold damages its fleshy tissue.4PubMed Central. Resilience of Portulaca plants to environmental stresses and the economic potential of their bioactive compounds This is why plant tags disagree: “annual” fits most buyers’ climates, while “perennial” describes its native warm range.
To find your zone, enter your zip code on the USDA hardiness zone map. Zones 10–11 cover places like south Florida, coastal southern California, and Hawaii. Zone 9 and colder usually means at least occasional frost, and that kills portulaca. A sheltered spot near a wall can help in a borderline year, though it’s not guaranteed.
One unusual cold snap in a warm zone can still kill portulaca. If your area has had a freeze in recent winters, plan on a one-summer plant.
Even in zones 10–11, portulaca survives winter but grows much more slowly in short, cool days.5PlotMyGarden. Portulaca: Planting, Care & Companion Flowers Warmth and long days speed up its growth and flowering,6Sakata Ornamentals. Portulaca Culture Guide so a plant may look sparse in winter and recover in spring. Thin, leggy stems with few flowers are slowed growth, not death. Stems that are still plump and firm are a good sign, while mushy or blackened ones are damaged and should be trimmed off. A slow plant uses little water, so wait for new growth in spring before resuming normal watering and feeding.
Moss Rose Versus Common Purslane
Common purslane is a succulent annual herb found in nearly every part of the world.7PubMed. Genetic improvement of purslane (Portulaca oleracea L.) and its future prospects It is a widespread summer annual weed of gardens and fields,8Weed Technology. Vegetative Reproduction Potential of Common Purslane (Portulaca oleracea) though in tropical climates it can persist as a perennial.9PubMed Central. Resilience of Portulaca plants to environmental stresses and the economic potential of their bioactive compounds
The familiar moss rose (Portulaca grandiflora) is usually grown as an annual and comes in many flower colors.10Radiation Botany. Use of Gamma Irradiation in the Production of New Varieties of Perennial Portulaca A perennial form exists, with double carmine flowers and little variety in color or shape.11Radiation Botany. Use of Gamma Irradiation in the Production of New Varieties of Perennial Portulaca That form is easily grown from stem cuttings.12Radiation Botany. Use of Gamma Irradiation in the Production of New Varieties of Perennial Portulaca So a moss rose sold in a mix of colors is almost certainly meant to be treated as a summer annual.
In your yard, the leaves are the easiest giveaway. Moss rose has narrow, needle-like leaves and showy, rose-like flowers. Purslane has flat, paddle-shaped leaves and tiny yellow flowers. Both have thick reddish stems that spread low along the ground, and purslane often appears unplanted in cracks and bare soil.
If you can’t tell which one you have, start with where it came from. A plant you bought and placed is likely moss rose or a hybrid, while one that appeared on its own is often purslane, though moss rose can self-seed too. Flowers help if there are any. A young seedling with no blooms is better judged after a few weeks of growth, when the differences become clearer.
Both share the same fleshy tissue that cold damages, so treat any portulaca as killed by frost unless your zone is 10–11. Where they differ most is seed: purslane’s reputation for coming back is much stronger than moss rose’s.
Why Portulaca Seems to Come Back on Its Own
Purslane seeds have sprouted after 30 and even 40 years buried in soil.13Cornell University. Common purslane One summer of plants going to seed can therefore supply seedlings for many years. In one field, two seasons without new seed cut most weed seed stores by about a third, but purslane seed stayed plentiful.14Canadian Journal of Plant Science. Weed emergence and seedbank after three years of repetitive shallow cultivation in a muck soil field
Moss rose flowers close and fade, then leave small capsules that split open and scatter very fine seed. Because the seed is tiny, wind, rain, and soil movement can carry it, so seedlings sometimes appear away from the original pot or bed.
Frost kills the parent, but its seeds in the soil aren’t damaged the way fleshy stems are. A seedling that appears in spring is a new plant, not the old one regrowing, which is why a gardener can mistake a new generation for a perennial.
Moss rose seeds need light to sprout, so they should be barely covered.15The Spruce. How to Grow and Care for Moss Rose In lightly moist soil they sprout in about two weeks.16The Spruce. How to Grow and Care for Moss Rose Seed dropped on the surface the year before sprouts readily once soil warms. Seeds buried deep or hidden under thick mulch may stay dormant instead, while digging or hoeing can bring buried seed to the surface and trigger a flush of seedlings.
Self-seeded moss rose usually shows up in late spring after the soil warms, often weeks after bedding plants would have gone in. The seedlings can come up in different colors than the parent hybrid, and they may be fewer or patchier than the original planting.
If you want volunteers, leave late flowers to form seed pods and avoid deep mulch over the bed. If you don’t want purslane, pull it before it flowers so it stops adding seed, and remove weeds in spring before pods ripen.
How to Keep Portulaca Alive Over Winter
In a cold climate you can carry a plant through indoors. Move containers inside before the first frost of the season.17Gardening Know How. Portulaca: Complete Plant Care And Growing Guide Purslane should come in once nights fall below 40°F,18Plant Addicts. Purslane Winter Care which is earlier than frost, so watch the forecast. Check the plant and soil for insects first so pests don’t spread to your houseplants.
Cut the plant back to about a third of its size and set it in a sunny window.19Plant Addicts. Purslane Winter Care Water only when the soil is dry.20Plant Addicts. Purslane Winter Care Expect slow growth, because the plant may be semi-dormant.21Plant Addicts. Purslane Winter Care Skip heavy fertilizer since there is little growth to feed, and put the plant back outside only after the last spring frost, easing it into full sun over a week or so. The common indoor mistakes are overwatering in low winter light, which rots the fleshy stems, and using a dim room, which makes plants stretch and flop.
Cuttings are an easier way to save a favorite. Purslane roots readily from cut stems,22Weed Technology. Vegetative Reproduction Potential of Common Purslane (Portulaca oleracea) and moss rose cuttings with red stems root better than green ones.23Journal of the Japanese Society for Horticultural Science. Physiological studies on the adventitious root formation in cuttings of Portulaca grandiflora HOOK. I Leaves supply the root-forming signal, so keep some leaves on the cutting.24Journal of the Japanese Society for Horticultural Science. Physiological studies on the adventitious root formation in cuttings of Portulaca grandiflora HOOK. I A few leafy cuttings in water or soil can carry a plant through winter in little space.
Take 3–4 inch tips in late summer, before nights cool. Remove only the lowest leaves and set the stems in moist, gritty potting mix. Keep them in bright light until new growth shows that roots have formed, then plant outdoors after the last spring frost.
Why Portulaca Handles Heat and Drought So Well
Portulaca is one of the few plants that can switch between two ways of taking in air to make food, especially under drought.25PubMed. Salinity and drought suppress C4 and induce CAM metabolism in two Portulaca species Most plants take in air through leaf pores during the day, and lose water through those same pores. When water runs short, portulaca shifts toward a mode that takes in air at night and loses less water.26PubMed Central. Exploring C4–CAM plasticity within the Portulaca oleracea complex It stores what it takes in and uses it during the day with its pores mostly closed. The switch is fully reversible once water returns.27PubMed Central. Exploring C4–CAM plasticity within the Portulaca oleracea complex
The thick, juicy leaves help too. The water stored in them is drawn down to keep the plant working during dry spells.28PubMed. Photosynthetic and anatomical characteristics in the C4-crassulacean acid metabolism-cycling plant Portulaca grandiflora They act like small tanks: they buy time, and the switch slows the rate of water loss. A drawn-down leaf may look slightly shriveled or flat, then plump up again after a drink.
For care, water sparingly, since soggy soil is a bigger threat than drought. Plant in full sun and well-drained soil.
Leaves that droop in afternoon heat but look normal by evening are usually coping with heat, not dying. Leaves that stay limp in the morning, or stems that turn soft, point to a deeper problem such as too much water. Check the soil a finger-depth down before watering, since dry on top and wet below is common.
A Bonus If You Have Purslane
Purslane has more of a plant omega-3 fat than any other leafy green.29PubMed Central. Purslane Weed (Portulaca oleracea): A Prospective Plant Source of Nutrition, Omega-3 Fatty Acid, and Antioxidant Attributes 100 grams of fresh leaves provides about 300–400 mg of that omega-3.30PubMed. Common purslane: a source of omega-3 fatty acids and antioxidants It also has more vitamin E, vitamin C, and the antioxidant glutathione than spinach.31PubMed. Common purslane: a source of omega-3 fatty acids and antioxidants The leaves hold more of this omega-3 than the stems,32PubMed Central. Nutritional Value, Chemical Composition and Cytotoxic Properties of Common Purslane (Portulaca oleracea L.) in Relation to Harvesting Stage and Plant Part so favor leafy tips over thick stalks. Because it keeps growing back, you can harvest it repeatedly, and snipping tips encourages branching.
Eat only common purslane, not ornamental moss rose. Common purslane has flat, paddle-shaped leaves, while moss rose has narrow, needle-like ones. Harvest young tips from unsprayed areas and use them raw in salads or lightly cooked; they taste lemony and crisp. Watch for spurge, a toxic look-alike: break a stem, and spurge oozes milky sap, while purslane’s sap is clear. Don’t eat a plant you can’t confidently identify, and ask a knowledgeable local gardener if unsure.