Marshmallow Plants Are Known for Their Healing Properties—Here's How to Grow and Care for Them

If you love gardening, then you likely do a little experimenting with the greenery you grow every now and then. When it comes to adding to your garden come the fall, consider sowing marshmallow plants. While you might think of making s'mores when growing the plants, they are not what you think. Formally called Althaea officinalis, these plants bloom in the springtime and have been known to reduce inflammation, according to the Missouri Botanical Garden. Plus, they are not too hard to grow, so long as you plant them with access to direct sunlight and moist soil.

How to Grow Marshmallow Plants

Growing from Seed

The marshmallow plant is best grown from seed. Start by sowing them outdoors in the fall. By spring, they will start to grow. "Germination rates for this plant are naturally quite low, and so a period of cold stratification is recommended to increase the chances that the seeds will germinate," says Justine Kandra, ahorticulturist at Missouri Botanical Garden's Kemper Center for Home Gardening. Pro tip: The marshmallow plant seeds can also be kept in a bag of moist sand in the refrigerator for 40 to 60 days in the winter.

1. Kandra says that once this period of indoor cold stratification has passed, the seeds can be potted up in a seed tray under a thin layer of soil, placed in a sunny window or under a grow light, and kept moist until they begin to sprout in 1 to 2 weeks.
2. After a few more weeks of growing indoors, the plants should be ready to be hardened off and planted in the garden.
3. "Mature marshmallow plants will reach around 4 feet tall and 2.5 feet wide, so leave 2 to 3 feet between each plant," says Kandra.
4. Marshmallow clumps can be divided in the fall and transplanted, but this can be difficult given their extensive, thick root system, Kandra says.

Growing from Cuttings

"Plants can also be propagated from cuttings in spring, or division of the strong spreading root systems in late fall or early spring before they have started to grow," says Marc Hachadourian, the director of glasshouse horticulture and senior curator of orchids at The New York Botanical Garden. He explains that these are vigorous garden plants and will often reseed in place and make a spreading clump over time. "They are attractive garden plants with silver-green leaves and small cupped white blooms that look like miniature hibiscus blooms," he adds.

Light, Soil, and Climate Conditions

Marshmallow plants thrive in full sun and moist soil, primarily in USDA Hardiness Zones 3 to 9. "While the plants will tolerate some shade, they can get leggy and are best in full sun," says Hachadourian. "As their common name of 'marshmallow' suggests, they grow well in wet locations and soils with regular moisture."

The greenery grows best in Pacific Northwest regions because of all of the rainfall. "They will grow well in typical garden soil, and are tolerant of a wide range of conditions, including wet sites and heavy, clay soils," says Kandra. "They will even tolerate brief periods of drought once fully established." However, the plants will not grow well in shady areas, or in soils that are too dry, like in mountain or desert climates.

How to Care for Marshmallow Plants

To care for the plants in the garden, they will need the same care as any other garden perennial. "Regular watering, a spring application of fertilizer, and cut back in the fall to winter" are necessary, according to Hachadourian. "As plants grow over time, they can be lifted and divided to propagate or reduced in size," he adds. "The plants can be cut back after blooming to prevent seeds from forming or to control the height of the plants."

How to Harvest Marshmallow Plants

After two years or more, Hachadourian notes that you can harvest in the fall. From there, remove the thickened roots. "The remaining crowns can be replanted and allowed to grow, but it will take some time for the roots to regenerate," he says. "The roots are then peeled and boiled to create the thick mucilaginous substance that is used to create marshmallow and can be even used as an egg white substitute." These can be peeled and dried. Kandra explains that they are rich with nourishing properties, like starch, mucilage, and pectin.