Althaea is a small family of flowering perennials consisting of no more than 12 species. The best known of these are the wild marshmallow plant, hollyhock and Rose of Sharon. All of these look similar and have large, showy flowers. Along with being a popular addition to flower gardens, althaea is a medicinal herb used to treat a wide range of conditions.
The color and size of althaea flowers depend on the individual species. The hollyhock has single or double blooms in a wide range of colors, including pink, rose, yellow, white and a very dark purple that is almost black. The marshmallow, however, always produces very pale pink four-petaled flowers. Between five and eight flowers bloom on each flower stalk of these two species throughout the summer. Rose of Sharon flowers are either single or double flowers in solid or bi-color shades of pink and white; they appear from late summer into early fall.
Most varieties of althaea have large fleshy leaves growing in a cluster near the ground. The leaves get smaller and less plentiful as they grow up the stalks, with few at the top near the flowers. These plants reach 5 feet (1.5 m) tall or more. The Rose of Sharon is different, growing into a large shrub with smaller leaves growing all along its branches.
Marshmallow plants are frequently seen growing along riversides and in marshes, as well as through fields and along roadsides and ditches. Hollyhocks and Rose of Sharon are strictly garden plants and usually stay within their boundaries. They all require moist soil and should be kept well watered in hot weather and during drought. Very dry soil will prevent these plants from blooming, and the buds will simply drop off the plant.
Propagating althaea is easily done from seed, though the resulting plants may not produce flowers until the second year of growth. New plants can be planted in early fall to give them plenty of time to become established before winter. In warmer areas, they can be planted anytime.
Althaea is prone to damage from aphids and Japanese beetles. The predators will quickly strip the leaves of these plants, leaving very little uneaten. Aphids can be removed by a strong spray from a garden hose, because it is not easy for them to get back to a plant once they are on the ground. Japanese beetles are best removed by hand-picking them and dropping them into a jar of water. Spraying with insecticides is only necessary for severe infestations.
The marshmallow plant, Althaea officinalis, is used as an herbal remedy for a number of medical conditions. It is an anti-inflammatory with the ability to calm irritated body tissue. As such, herbalists use this species of althaea to treat respiratory problems such as bronchitis and pneumonia.
This plant is also a popular addition to skin care products and is said to promote more rapid healing of skin abrasions and rashes. The mucilage from the root of this plant is used in a poultice or compress to soothe and calm these conditions. The pain of bee stings also may be eased this way.