How to Grow Althaea – Marsh Mallow

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Althaea–commonly called marsh mallow–is a perennial often grown as an annual. It closely resembles the hollyhock (Alcea) but with smaller, usually stalked flowers. Althaea is often grown in moist, brackish habitats.

Althaea bears pink to purple, cup-shaped flowers on tall, erect stems in summer. The flowers are smaller than hollyhocks with notched petals. The flowers are borne on strong, wiry stems. Blossoming begins at the bottom of the stems and moves progressively upward. The stems are covered with flowers throughout the season. The round, toothed leaves just more than 2 inches long are pale green.

Althaea is a hardy plant that spreads to form clumps. Althaea is suitable for a sunny spot at the back of a border or they can be grown in a cottage or wildflower garden where the soil is moist.

Althaea is best started from seeds sown in summer for flowering the following year. Once established in a garden, new plants will grow spontaneously from seeds dropped during the summer.

Althaea is a genus of 12 species native to coastal habitats from Western Europe to Central Asia.

Get to know Althaea – Marsh Mallow

  • Plant type: Annuals and perennials
  • Growing zones and range: Zones 3-9
  • Hardiness: Hardy to Zone 3
  • Height and width: 4 to 6 feet (1.2-2m) tall and 12 to 24 inches (30-60cm) wide
  • Foliage: Broadly ovate, shallowly to deeply lobed, dark green leaves
  • Flowers: Racemes or panicles of small, 5-petaled flowers
  • Flower color: Pink to bluish purple
  • Bloom time: Summer to autumn
  • Uses: Herbacious border or wildflower garden
  • Common name: Hollyhock
  • Botanical name: Althaea
  • Family name: Malvaceae
  • Origin: Coastal habitats from Western Europe to Central Asia
Althaea officinalis, commonly called marsh-mallow
Althaea officinalis, commonly called marsh-mallow

Where to plant Althaea

  • Grow Althaea in full sun.
  • Plant Althaea in humus-rich, well-drained soil.

When to plant Althaea

  • Set container-grown Althaea in the garden in spring or autumn.

Planting and spacing Althaea

  • Space Althaea 12 to 24 inches (30-60cm) apart.

How to water and feed Althaea

  • Keep the soil moderately most for Althaea.
  • Fertilize Althaea with an all-purpose organic fertilizer in spring.

Althaea care

  • Stake plants on windy sites.

Althaea pests and diseases

  • Powdery milde, white mold and leaf spot can occur.
  • Althaea can be attacked by flea beetles, spider mites, and Japanese beetles.

Althaea propagation

  • Sow seeds of annuals indoors at 55°F (13°C) in late winter for transplanting out once they are well established. New plants often bloom the following year.
  • Sow seeds directly in the garden in midspring.
  • Perennials can be set in the garden in autumn after 2 or 3 true leaves have developed.
  • Divide existing clumps in autumn or spring.

Althaea varieties to grow

  • Althaea armeniaca. Perennial grows to 4 feet tall; bears funnel-shaped deep rose-pink flowers to 2 inches across on short stalks.
  • A. cannabina. Perennial grows to 6 feet tall; bears small, cupped lilac to deep pink flowers to 2 inches across; flowers sometimes have darker eyes,
  • A. officinalis, marsh mallow. Grows to 6 feet tall; bears small lilac-pink flowers to about an inch across usually on terminal clusters. Sometimes grown for medicinal use.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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