Althaea Plant Growing & Care Guide for Gardeners

In this Gardener's HQ guide, we'll explore cultivating Althaea plants in your garden, indoor spaces, and other settings.

Marsh Mallow Plant, Hollyhock, and Sweet Weed: Cultivation & Garden Use

The common names for the Hardy annual or perennial Althaea include Hollyhock, Marsh Mallow Mallards, and Sweet weed.

They typically flower from summer to early autumn.

Photograph of Althaea officinalis by Phil Sellens.

The mucilaginous roots of Althaea and the leaves have been used for many medicinal purposes in the past, especially for respiratory diseases and asthma.

Description of Althaea

Althaea are large plants, with older plants capable of reaching up to 200 cm in height. Althaea has double flowers of most colors. The leaves are lobed. It is ideal for growing in cottage gardens and as part of a butterfly garden as it is a favored food of many moths.

Information on Althaea and it's Commonly grown garden species

Althaea is a native plant of Europe and Western Asia, where it can be found on river banks and in salty marshland. The plants presence on marsh lands led to its common name of marshmallow.

The slimy root is sweet tasting and was used in the original recipe for the Marshmallow sweets.

The plants have long stems that may reach up to seven feet (2 M) in height, and typically have a single flower, with double petals atop the inflorescence.

Members of the Althaea genus are known to have many medicinal properties, in ancient times the roots were used to cure indigestion, reduce inflammation, asthma attacks, used against tooth and ear aches, and to help with diarrhea.

There are at least four species that belong to the Althaea genus. These are as follows:

Common Marshmallow: A. officinalis
Hairy Marshmallow: A.hirsuta
Palm-Leaf Marshmallow: A. cannabina
A. ludwigii

The genus belongs to the Malvaceae family, better known as the mallow family. This is a large family consisting of around 427 species across 49 genera. Therefore closely related species to Althaea include Rosemallow (Hibiscus), Mallow (Malva), Anoda, Hollyhock (Alcea) and Urena.

The plants are also referred to as Hollyhocks, and are closely related to the Alcea genus. Althaea plants tend to be shorter than Alcae.

Althaea Plant Species

Marshmallow (Althaea officinalis)

These plants are fairly hardy perennials and can grow in zones 3 through 9 in the USA, and throughout Europe.

Plants will reach between 48 and 72 inches (120 to 180 cm) in height, and therefore should be given plenty of space – 18 to 24 inches (45 to 60cm) – when sowing seeds out in the autumn.

They can be grown in either full sunlight or in partially shaded conditions and bloom with pale pink or white flowers from the middle if summer and through the start of autumn.

Ideally the soil will be of a pH ranging from 6 to 7.5.

Althaea cannabina (Hemp-leaved Marshmallow)

Althaea cannabina is a perennial plant that can reach up to 60 inches (1.5 m) in height. It has lobed, hemp-like leaves and small, pink, hollyhock-like flowers. This plant is commonly referred to as Hemp-leaved Marshmallow.

Photograph of Althaea cannabina by Chemazzgz.

Hemp-leaved Marshmallow is often grown in gardens for its beautiful, delicate flowers.

It prefers to grow in full sun and likes a well-drained soil. It is usually used in borders, cottage gardens, or naturalized areas, where its height can be fully appreciated.

Biennial / Annual Varieties of Althaea

Hairy Marshmallow, Rough Marshmallow (Althaea hirsuta), subspecies with longer petals (Althaea ludwigii)

These plants are native to Western Asia and the Mediterranean regions of Europe and Northern Africa.

They range from six to fifteen inches in height (15 to 40 cm) and usually has a single (or a couple) stem that is branched.

The leaves vary in shape depending upon their location on the stem with them having a longer petiole towards the bottom of the stem.

Grow in the same conditions as described above (How to grow Althaea).

How to Grow Althaea

It is best to sow perennial Althaea species such as Marshmallow and Hollyhock on the soil surface, with a spacing of 50 to 90cm in the autumn.

The plants enjoy to grow in either light shade or full sunlight. The soil should be well drained, rich and moist with a pH between 6 and 7.5

Indoors, Althaea requires between 10 and 15 days to germinate at a temperature of 15 to 20 degrees Celsius.

It is necessary to stratify the seeds first to initiate germination.

Plan to transplant annuals and perennials outdoors after the last frost of spring. When growing indoors prior to transplanting in the spring they should be grown in peat pots.

How to care for Althaea

Hollyhock, Marsh Mallow and other Althaea members are easy to take care of as long as they are well spaced, they requires regular watering in the summer and should be staked.

A second bloom is possible if flowers are removed prior to setting seed.

Althaea Growing Guide and Facts

Common Names: MarshMallow Plant, Marsh mallow, Hollyhock, Mallards, Sweet Weed, Hairy Marshmallow, Rough Marshmallow.
Life Cycle: Hardy annual. Hardy perennial.
Height: 6 to 80 inches (15 to 200 cm).
Native: Europe, Asia.
Family: Malvaceae.
Growing Region: Zones 3 to 9.
Flowers: End of spring to summer and/or autumn.
Flower Details: Pink, white, yellow, mauve. Single or double flowers. Flowers on spikes.
Foliage: Lobed. Palmate.
Sow Outside: Surface. Following the last frost. Spacing 10 to 40 inches (25 to 100 cm).
Sow Inside: Mix seeds in a growing medium; keep soil moist, place in a freezer bag, then stratify by refrigeration for two weeks. Use peat pots. Germination time: one to two weeks. Temperature 60 to 65°F (16 to 18°C). Seven or eight weeks in advance. Transplant outdoors following the last frost or in autumn.
Requirements: Full sunlight or partial shade. Good drainage. Soil pH 6 to 7.5. Moist soil. Sandy soils. Provide support. Water regularly. Deadhead.

Common Questions

How many members does the Althaea genus have?

The Althaea genus includes about 12 species.

Do members of Althaea make a good garden or landscaping plant?

Yes, Althaea, commonly known as Marshmallow plants, are known for their showy flowers and foliage.

Which Althaea species are most frequently grown by gardeners?

The most commonly grown species is Althaea officinalis (Marshmallow).

Are members of the Althaea fragrant?

Some Althaea species, such as Althaea officinalis, can have a mild, pleasant fragrance.

What is the perfect location to grow Althaea?

Althaea plants prefer full sun to partial shade and well-drained soil, and can tolerate a variety of soil conditions.

Is Althaea invasive in the USA, if so in which states?

Althaea is not thought invasive in the USA.

How do I remove Althaea from my garden?

Removal can be done by digging up the entire plant, ensuring to get all the roots to prevent regrowth.

Summary

The Althaea genus, also known as Hollyhock, consists of perennial plants with tall flower spikes and colorful blossoms. Native to Europe and Asia, Althaea plants are cherished for their vibrant flowers and attractive foliage. They thrive in well-drained soil and prefer full sun exposure, although they can tolerate some shade. Regular watering is essential, especially during dry spells, to ensure optimal growth.

Cultivating Althaea requires providing support for the tall stems and can be achieved through staking or trellising. These plants can be propagated through seeds or division. Althaea species are commonly used in cottage gardens, borders, or mixed flower beds to add height, charm, and a nostalgic touch to garden designs. Their range of colors and delightful flowers evoke a sense of nostalgia and are sure to attract attention and admiration in any garden setting.

I hope that you enjoyed this guide on Althaea. You may also enjoy the following garden growing guides: How to grow Malva and Hibiscus plants.