Gardens Illustrated
Hollyhocks
© Alamy

Hollyhocks: how to grow alcea

Published: June 1, 2022 at 12:13 pm
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Hollyhocks are famously tall and pretty, and if you grow them as annuals, they should stay healthy and strong. Plantsman John Hoyle is your guide to how to grow hollyhocks, and recommends his favourite cultivars. Photographs Torie Chugg

British gardeners have grown the wild hollyhock, Alcea rosea, since the mid-16th century, when it arrived from China or western Asia. This species is part of the Malvaceae family, which includes other familiar garden plants such as Abutilon, Sidalcea and Hibiscus.

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The colour of hollyhock flowers ranges from pure white to dark purple, and plant breeders have produced cultivars with double and semi-double flowers. They are naturally perennial but in the garden can be treated as biennial and, sometimes, as annual plants.

Some produce flowers in the first year after sowing, so can be used as annuals. These include Alcea rosea ‘Halo White’, which looks particularly dramatic when grown with the almost black cultivar Alcea rosea ‘Nigra’.

New hybrids are bringing the original toughness, stature and vibrancy into plants that are disease-free, so hopefully many more gardeners will rediscover the charms of hollyhocks.

Althaea cannabina
Althaea cannabina © Torie Chugg

What are hollyhocks and when do they flower?

Originating from China and western Asia, hollyhocks are cultivars of Alcea rosea, plus related species in the mallow family. Hollyhocks grow up to 2.5m tall, flower from July to late summer and attract bees and butterflies.

How to grow hollyhocks

Where to grow hollyhocks

In general the claim that a plant ‘will grow anywhere’ has to be treated lightly but Alcea and Althaea really are plants that will tolerate a wide range of growing conditions. At their best in fertile, well-drained soil in sunny positions, they will cope with shade and poor, heavy soil.

Plant in cottage garden schemes; at the back of borders; beneath sunny walls; with other self-seeding plants in gravel gardens and in naturalistic plantings.

How to grow hollyhocks from seed

Sow the seed of Alcea rosea cultivars in a patch of spare ground during the summer. At the beginning of autumn the seedlings should have three or four true leaves and can be transplanted to the spot where you want them to flower.

Problems with hollyhocks

All cultivars of Alcea rosea will, sooner or later, become covered in hollyhock rust, Puccinia malvacearum. This fungus is specific to plants in the Malvaceae family. Not only is it an eyesore but it also has a debilitating effect on the plant.

The traditional method of dealing with rust is to spray with a fungicide, beginning in May and continuing through the summer.

A more reasonable solution is to treat hollyhocks as annual or biennial plants, removing and burning the infested ones as soon as they have finished flowering. You will still get rust on your plants but it won’t completely disfigure them.

The best hollyhocks to grow

Althaea officinalis

Althea officinalis
© Torie Chugg

The marsh mallow is a British native that grows to about 90cm tall. The tough foliage is grey and velvety and in August the plant is covered with small pale pink, almost white, flowers.

Althaea cannabina

Althaea cannabina
© Torie Chugg

Despite its name, its foliage is only vaguely reminiscent of cannabis. Its flowers, pale pink with a raspberry centre, are like miniature hollyhocks, held on wiry stems up to 2m tall.

Alcea rosea ‘crème de cassis’

Alcea rosea 'Creme de Cassis'
© Torie Chugg

This flamboyant cultivar bears large flowers, 7.5cm wide, from June to August. Unusually, flowers may be both single and double on the same plant. 2m tall.

Alcea rosea ‘nigra’

Alcea rosea 'Nigra'
© Torie Chugg

Although known as the black hollyhock, its flowers are actually deep purple. It is worth buying new seed each year rather than collecting your own from this plant as home-collected seed tends to produce pale imitations of the true form. 2m tall.

Althaea armeniaca

Althaea armeniaca
© Torie Chugg

The 2m-tall stems are covered with small flowers from late summer to autumn. Impressive both at the back of a border and as a veil to look through to other plants.

x Alcalthaea suffrutescens ‘parkrondell’

Alcea x Althaea 'Parkrondell'
© Torie Chugg

One of a new breed of hollyhocks bred in Hungary. It grows to 2m tall and has grey, velvety foliage that makes the plant attractive even before it starts to flower.

Alcea rosea ‘Halo white’

Alcea rosea ‘Halo white’
© Torie Chugg

Produces flowers in its first year after sowing, so is one of the cultivars that can be used as an annual. It looks dramatic when grown with the almost-black Alcea rosea ‘Nigra’. 2.5m tall.

Alcea rosea Chater’s Double Group white-flowered

Alcea rosea plena 'Chaters White'
© Torie Chugg

The neat pom-pom flowers grow so densely that the stem seems to disappear as the flowers open. Grows to a height of 2m.

Alcea rugosa

Russian hollyhock (Alcea rugosa)
© Torie Chugg

A long-lived perennial hollyhock that will grow in shade as well as sun. The flower’s petals are almost translucent. Shorter than most hollyhocks, growing to about 1.5m tall.

x Alcalthaea suffrutescens ‘Parkallee’

Alcea x Althaea 'Parkallee'
© Torie Chugg

Much more rust-resistant than perennial hollyhocks, this is a sub-shrub that produces new shoots each spring from the base of the previous year’s stems. The flowers appear along the length of its 2m tall stems.

Where to buy hollyhock seeds

Chiltern Seeds. Tel 01229 581137, chilternseeds.co.uk

Nicky’s Nursery. Tel 01843 600972, nickys-nursery.co.uk

Thompson & Morgan, tel 0844 2485383, thompson-morgan.com

Where to buy hollyhock plants

Cotswold Garden Flowers, Sands Lane, Badsey, Worcestershire WR11 7EZ. Tel 01386 422829, cgf.net

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Elizabeth MacGregor, Ellenbank, Tongland Road, Kirkcudbright DG6 4UU. Tel 01557 330620, elizabethmacgregornursery.co.uk

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