Portulaca, or moss rose, is a colorful, hardy annual that’s as tough as it is attractive. Drought tolerant and heat resistant, these easy-care South American natives perform well as bedding plants, rock garden specimens, borders and ground covers. Your moss roses will begin blooming in early summer, and flower continuously well into the fall. Start portulaca seeds indoors about 8 weeks before the last predicted frost date for your area.
Cut the top off of an empty cardboard egg carton. Poke several holes in the bottom of each "cell" or egg holder with a toothpick. Fill the cells to about ¼ inch from their tops with fine garden soil or a commercial seed-starting mix. Set the seed flat in a shallow container of warm water until the soil surface feels moist to your touch. Remove the flat from the water and allow it to drain for several hours.
Sow a single portulaca seed in the center of the soil in each cell of the flat. Don’t cover the seeds with soil because they require plenty of light for germination.
Set the seed flat in a warm, brightly lit area out of direct sun. The best temperature for successful germination is between 68 and 86 degrees F. The top of your refrigerator or above a hot water heater are good locations provided there is enough light available. Your portulaca seeds will germinate in 10 to 15 days.
Check the soil daily. Water as needed to keep the seeds from drying out. The soil should be evenly moist, but not soggy or wet.
Cut the cells of the flat apart when all danger of frost has passed. The seedlings will be about 2 inches tall. Plant your portulaca seedlings in the paper cells about 6 to 10 inches apart in a sunny garden spot.