Althaea (Althaea officinalis), also known as the common marshmallow, is a member of the family Mallow. There are several members in this family including hibiscus syriacus. This family includes the common hibiscus and hollyhock. They are commonly found in coastal brackish or freshwater marshes in planting zones 8 and lower. Flowers bloom in colors of pink to lavender and form into clusters on plants with toothed and slightly hairy leaves. Althaea is easy to grow, and is quite hardy once it has established itself.
Grow the Althaea in a location in your landscape that receives full sun and is warm for best growth and flowering. Althaea will tolerate growing in some shade, but will flower best if situated in a location receiving sun.
Consider the plant's size when choosing a location to grow Althaea. It can reach a height of 8 to 12 feet at maturity, with a width of 6 to 10 feet. It can be grown either as a shrub or pruned to make a small tree.
Grow the Althaea in soil that is rich in organic material such as compost, peat or manure and drains very well. Althaea will not perform well in soggy or dry soils. Amend the planting site before placing the plant into the ground with organic material, working it down at least one foot into the soil.
Water the Althaea twice a week during the warmer months of the year. Water plants once a week during the wet winter.
Fertilize in early spring, summer and fall with a 10-10-10 all-purpose granular fertilizer. Water the fertilizer in well. Apply a fresh coat of compost on top of the planting's sites soil in spring.
Use insecticides specifically recommended for use on Althaea. Blight, aphids, leaf spot, scale and whiteflies can sometimes be a problem.