Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
When I was a child, portulaca was a popular ground cover. I loved its rose-like flowers and fat succulent leaves. Then it seemed to go out of style. I’m so happy to see it regaining popularity. It’s a colorful, tough and versatile bedding plant.
What Is Portulaca?
Portulaca, also known as moss rose, is an annual plant that is related to purslane. The foliage is so similar that you should be careful in the spring when you are weeding purslane out of your garden that you don’t weed out portulaca seedlings too! It’s easy to tell them apart if you look carefully. Purslane leaves are flatter while portulaca leaves look like fat, fleshy pine needles.
Full grown portulaca plants are only 6 to 8 inches tall. Their thick leaves mean that they are drought tolerant. Be careful not to over water them. Grow portulaca in well-drained or even sandy soil. It is salt tolerant so it’s perfect for gardens and containers near the ocean. The plants need full sun, 6 to 8 hours per day, for best growth and bloom.
The flowers can be single, double or semi-double. They come in a variety of colors including red, orange, yellow, pink, violet, white and cream. They can also be bi-color. Bloom time is from mid-summer until frost. The flowers open in the morning and close at night. If the day is very cloudy, they may not open at all. When grown in partial shade conditions, the flowers will close during the shady part of the day.
A big drawback of this plant is that it is a prolific self-sower. You will want to keep this one deadheaded so that it doesn’t produce a lot of seed that will sprout all over your garden next spring. Deadheading will also encourage your plants to keep blooming until they are killed by a hard frost in the fall.
The Best Places to Grow Portulaca
Portulaca is a very versatile plant. It can be used as a ground cover because it is so short. Or you can use it in your rock garden along with your short alpine plants. It’s a great cover for areas where you grow spring bulbs. Its sprawling habit will cover the empty spaces after the foliage of your bulbs dies. Its tolerance of dry conditions means that it you won’t need to worry about your bulbs rotting in the ground from too much water.
Portulaca also drapes nicely when planted in containers and hanging baskets. Because it requires little water, it is perfect to tuck into stacked stone walls and between pavers in paths. Or it can be used as an edging along paths and flower beds.
How To Start Portulaca Seeds Outdoors
Thanks to its propensity for self-sowing, portulaca is very easy to grow from seed. You can direct sow it in your garden after your last frost. Ideally the soil should be 65⁰F. The seeds are very tiny so the easiest way to sow them is by mixing them in sand. Broadcast the sand and seed mixture over the area where you want your portulaca to grow. This will ensure even coverage of the seeds. However, do not cover the seeds with soil. They need light to germinate. Gently tamp the soil to ensure good contact between it and the seeds. I usually water the soil before planting fine seed like portulaca because the seed will wash away if you water with a garden hose or watering can after planting. Germination should occur within 10 to 14 days. If necessary, thin your seedlings to 6 inches apart.
How to Start Protulaca Seeds Indoors
If you prefer, you can start your seeds indoors 6 to 8 weeks before your last frost. Surface sow the seeds. Do not cover them. They need light to germinate. You can hasten germination by using a heat mat, otherwise expect your seeds to germinate with 10 to 14 days. You can transplant your seedlings outdoors in your garden after your last frost. Seedlings should be spaced 6 inches apart. Be careful while transplanting. Portulaca does not like its roots disturbed.
Germinating your seedlings in biodegradable peat pots or cowpots allows you to plant the entire container in the garden without disturbing the plants’ roots. The pots will decay into the soil, adding nutrients, during the growing season. An alternative to purchasing biodegradable pots is to make your own using paper or newsprint. A quick search on Youtube shows that there are many ways to make these pots. One caveat is to use plain paper or newsprint only. Glossy magazine pages do not break down as easily in the soil and the inks may contain heavy metals. The ink used in newspapers is vegetable based so it won’t harm your plant or your soil.
Questions & Answers
Question: I live in Montana. My daughter brought home a portulaca from a local gardening store. The weather here can get pretty brutal at times. Will a portulaca survive in Montana?
Answer: Portulaca is an annual so your winter weather is not a factor. Your summer weather should not affect how it grows. Just make sure that it gets enough sunlight and don't overwater. Portulaca likes to be a little dry.
Question: Is portulaca harmful to dogs, if eaten?
Answer: Portulaca is not harmful to animals. I this for sure because a rabbit ate all of my portulaca plants this spring! He is still alive and still munching his way through all the garden beds in the community garden where I have a garden.
Question: Will Moss Roses come up on their own for the second year?
Answer: Yes, portulaca seeds will germinate on their own in the spring. Portulaca is an annual, which means that it will only live for one growing season. If you see it again in your garden the following year, what you are seeing is plants that have grown from seeds that were dropped on the soil the prior year.
Question: Does portulaca come back the next year via seed even in cold weather climates/ zone 4?
Answer: Unfortunately, the seed will only survive the winter as far north as zone 5. If you allow the flowers to go to seed in the fall, you should be able to collect the seed to sow the following spring. Keep the seed cool during the winter. I keep my seeds in my refrigerator.
Question: Why does my portulaca not germinate well?
Answer: My best guess would be that you are covering the seeds. Sow them on the surface of the soil and don't cover them at all. The seeds need light to germinate. If you cover them with soil, they will not germinate.
Question: What type of soil should I use to grow Portulaca in containers?
Answer: You can use any kind of regular potting soil. Look for one that has time release fertilizer so that you don't have to worry about fertilizing while the plants are growing and flowering.
Question: Is the Portulaca plant or flowers edible?
Answer: No, neither the foliage nor the flowers are edible. Portulaca are for ornamental use only. They look like purslane which is edible, but the plants are unrelated.
Question: Will my moss rose plants be happy in Manchester, England?
Answer: Yes as long are you are growing them in full sun (6 to 8 hours daily) and well-drained soil and not over-watering them.
© 2018 Caren White
Caren White (author) on July 13, 2018:
Linda, you are in luck. Portulaca is deer resistant. Thanks for reading and commenting.
Linda Lum from Washington State, USA on July 13, 2018:
This brings back wonderful memories. We had portulaca at our first home (newlyweds). I've not tried to grow them where I am now because they look so delectable--I've convinced myself that the deer would gobble them up, but I don't know that to be true. Do you know if they are deer proof?
Caren White (author) on July 13, 2018:
Mary, I hope they will be a happy reminder of your childhood! Thanks for reading and commenting.
Mary Norton from Ontario, Canada on July 13, 2018:
We used to have these in our house when I was growing up but I haven't planted them in my own garden. I'll certainly do this next year.
Caren White (author) on July 12, 2018:
So glad to meet another fan of these flowers! Thanks for reading and commenting.
Peggy Woods from Houston, Texas on July 12, 2018:
I have grown these little moss roses (portulaca) many times in our garden. I love the colors and hardiness of this little low growing plant that offers almost continuous blooms throughout the growing season.