• The Lowdown on Portulaca: Growing Moss Rose from Seed

February 19, 2019

Some states are thinking about legalizing psilocybin (a.k.a. "magic") mushrooms for medicinal purposes, specifically to treat mood disorders and Post Traumatic Stress Disorder. If that happens here in Michigan, we won't get much work done since the first thing we'd do is plant about a square half-acre of Portulaca grandiflora. We'd sprawl out in that patch with our cheeks pressed against the soft spiky leaves, trying to focus on the seemingly endless landscape of crinkly rose-like one-inch blooms. Sure, we'd forward our office phone to our cells, but if we manage to pick up, you'll probably just hear faint "squeeeee" sounds, and lots of giggles...because we'll be pretending to be Gulliver. On shrooms.

Okay, hang on. You're here to learn about ornamentals here, not psychedelics, aren't you? Oops. Sorry. And anyway, drugs are bad, m'kay?

The truth is, you don't have to be high to enjoy portulaca. In fact, the closer to the ground you are—physically, at least—the more you'll appreciate this heat-loving succulent groundcover.

Taxonomy, history, and medicinal uses

Portulaca grandiflora is native to central South America, most specifically Brazil, Uruguay, and Argentina.

They're nyctinastic, meaning their flowers close at night and on overcast days. One of portulaca's common names is "eleven o'clock," and you can almost set your watch by the flowers' uncanny ability to open at precisely and consistently this hour in the morning. The French use the translation "Chevalier de onze heures" as their common name for Portulaca grandiflora. Here are some others:

  • Moss rose (and rose moss)
  • Mexican rose (uh, Mexico's nowhere near South America, guys)
  • Sun rose (name checks out)
  • Vietnam rose (Oh, come on, now)
  • Garden purslane (see below)

You may see Portulaca grandiflora referred to as "purslane." This nickname is typically reserved for the Old World species within the same genus. There's also a true rose called "moss-rose," but we figure that our customers are too brilliant to confuse portulaca with Rosa mucosa.

Portulaca derives from the Latin word for "little gate" (portula), and Uncle Carl Linnaeus thought of this when he examined the plant's "flip top" seed pod. Grandiflora translates to "large flowers," and while portulaca’s blooms are barely an inch across, they're relatively enormous for a ground-hugging plant with such delicate-looking foliage.

We'll use "little p" portulaca, P. grandiflora, and moss rose interchangeably in this article, as these are the names by which they're most commonly called. And, of course, we want to keep you alert.

Portulaca in the garden

Before you decide how you should grow your moss rose, you'll need to figure out if you're using them for their utility or their ornamental qualities. They survive in dry, sandy, somewhat depleted soils, but they thrive when you give them regular irrigation and lots of nutrients. Either way, you'll get plenty of flowers but under ideal conditions, their foliage will be greener and more thickly matted, and their flowers more prolific.

Portulaca plants are great for stabilizing sandy soils or hiding ugly spots on your property. Since they do well in the heat, they make good borders along the asphalt, concrete, and other heat-absorbing, thermal-mass surfaces that might "cook" more delicate plants in hot climates. Since they tolerate light foot traffic, you can plant them in between stepping stones and bliss out on the way they feel between bare toes. They'll take hold in the cracks in old stone retaining walls and cascade over the edges, and they'll sprawl over those often neglected strips of dirt between sidewalks and streets.

Portulaca is also an excellent potted plant, and you can even find it in some bonsai-inspired gardens. Grow them on living roofs with sedums such as stonecrop, or as a blending border for ice plant. Of course, they do well with non-succulents, too. Some gardeners like to use them to cover bulb beds. They help fight emerging weeds while letting the sword-like leaves of tulips and irises poke right on through.

While you can grow them in poor soils away from your irrigation zones, they do best in more posh conditions. These are our down-and-dirty tips for growing Portulaca grandiflora to its full potential, with some basic facts about the plant's growth habit:

  • USDA Hardiness Zones: Heat-loving hardy/half-hardy annual in USDA Hardiness Zones 2 through 11.
  • Sunlight Preferences: Full sun. Shade will prevent the blooms from opening up and will encourage scraggly stems.
  • Moisture Requirements: Intermittent watering; If very sandy soil, water more frequently; humus-rich soil, let dry out briefly in between irrigation.
  • Soil Preferences: Must be well-drained. Prefers compost-rich soil with a pH between 5.5 to 7.0.
  • Plant Height: Typically 3" to 8", very infrequently up to 12" tall.
  • Plant Width: 8" to 14", but sometimes up to 2'.
  • Growth Habit: Spreading, prostrate.

Portulaca blooms from June up until the first fall frost. The flowers resemble old-fashioned roses and may be single or double-layered. The petals are somewhat wrinkly, resembling crepe paper, and colors range from yellow, orange, pink, red, and white. We offer a double-flowered portulaca mixture with all these colors.

Bright yellow anthers at the centers of the quarter-size blooms add some extra cheer as if they weren't already giddy enough. The flowers themselves grow at the tips of reddish stems. Portulaca grandiflora's rich green leaves are fleshy and cylindrical with pointed tips, growing about 1/2" long in an alternating fashion. Once the flowers fade, the leaves at the end of the stems resemble star-shaped crowns behind the seed pods, which open into cups when the tiny black seeds are ripe.

Pests, disease, and maintenance

Aphids and other juice-loving bugs take a liking to rose moss, but they don't usually do too much damage. A quick spray with a hose early in the day will often get rid of them, or you can use your favorite insecticidal soap.

Rose moss is very susceptible to rot, especially since it has a very shallow root system. Don't ever let them get soggy, and if you live in an extremely humid area, be sure to let them dry out in between watering.

These annuals reseed readily and you'll likely have a fresh crop every season. Deadheading will help keep the plant looking tidy, encourage new blooms, and prevent new generations. The best way to maintain dense foliage is to provide your portulacas with full sun, lots of heat, and quality soil; otherwise, you might want to try trimming leggy branches for the best effect.

Feed your moss rose with a nitrogen-heavy fertilizer when they're young, switching to a phosphorous-heavy plant food just before they get ready to bloom. You can fertilize them again halfway through the flowering period if you'd like.

Growing Portulaca grandiflora from seed

Moss rose would rather be dragged on a world-wide Phish concert tour than endure transplantation, so we recommend sowing your seeds directly in the garden or your outdoor containers. You don't need to subject them to cold or soaking treatments, but because the seeds are super-tiny, you might want to mix them with fine sand if you plan to scatter them on the soil surface.

Tips for Raising Dirty Kids:

  • If you have a magnifying glass or a kids' microscope, take a moment to have a look at your portulaca seeds up close. They look like tiny black snail shells (the flat, coiled kind).
  • You can help your child create a "fairy garden" in a wide, shallow container with these scaled-down plants.

Plant your portulaca seeds outdoors as soon as you're free and clear of your last frost date. Remove any clumps and debris from the top inch of the soil, and work in screened, well-aged compost. You can scatter your moss rose seeds or gently rake them into the surface, but be sure not to cover them more than 1/8". They need some sunlight to germinate, and shouldn't be allowed to dry out until they've become well-established.

Ideal plant spacing is 12", but you can thin them if they get too crowded. The plants are easy to remove at any stage of growth. Portulaca germinates quickly in ideal temperatures (70°F to 80°F) so look out for seedlings 7 to 14 days after planting.

If you're stubborn and you really, really want to try growing portulaca from seed indoors, grow them in shallow nursery flats or cells. Add some garden sand to the potting soil, and take great care when transplanting them into their outdoor beds. You'll want to use fluorescent heat lamps and a heated seedling mat. Spray the trays with a misting bottle to keep the soil moist.

Get growing with Seed Needs

We're thinking about all our hot-climate gardeners right now as we recover from the 2019 Polar Vortex. We've never been so excited about spring, and we're pretty sure you're looking forward to your garden kicking in. As for other stuff kicking in, we don't condone any mind-altering substances. A healthy, vibrant garden is euphoric enough.

Okay, that and a lavender-infused vodka martini or three.

Contact us if you're ready to experiment with growing portulaca from seed or if you have any questions we haven't answered here. And if you have a lot more ground to cover than you can attain with a packet or two of seeds, we might be able to work out custom quantities. Just don't wait too long! Our supply is limited since we only carry fresh seeds that we expect to sell in a single year.


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