How to plant and grow hollyhocks

The Amazons of the summer border, hollyhocks tower on 1.5 to 2.5-metre stems from June to August. Their funnel-shaped blooms, which open in shades of ivory, lemon, pink, red, and plum, can often be seen peeping over a garden wall, basking in the sun. Bumblebees love to sup the nectar, and, as they do, become covered in a dusting of the flowers’ plentiful cream pollen.

These quintessential English cottage garden plants are in fact forms of a cultigen from Turkey – Alcea rosea – which had arrived in Britain by the fifteenth century. It’s said that Eleanor of Castile, the first wife of Edward I, brought hollyhock seeds back from Palestine much earlier, in the thirteenth century, having accompanied Edward there in the Crusades. The name hollyhock stems from the Anglo-Saxon holi (referring to the Holy Land) and hoc (mallow).

The hollyhock genus Alcea grows wild from the Mediterranean to Central Asia and comprises 82 species. Belonging to the mallow family, they are similar in make-up and appearance to lavatera, hibiscus, and, of course, marsh mallow (Althaea officinalis), the root of which was used by the ancient Egyptians to make restorative sweets.

By the seventeenth century, hollyhocks were much-loved garden plants and continued to be for three hundred years. Charles Darwin was obsessed with them and their natural process of hybridisation, and today they still grow in the garden of Down House, where he lived and worked. They fell out of fashion when they were hit by the fungal disease rust in the late nineteenth century. But now that we know how to prevent and reduce it – for instance, by growing the Halo series – these wonderful statuesque plants are enjoying a resurgence in popularity.

Hollyhocks are also part of the trend in growing flowers for the kitchen. Along with other edible blooms, such as nasturtiums and calendula, sweet-tasting hollyhock petals can be added to salads, used as a garnish, or brewed into tea.

Hollyhocks are short-lived perennials that are best treated as biennials (plants that live for two years, usually flowering in their second year) to keep them healthy. But there are close relations that live for a lot longer.

The most widely available hollyhocks bear double flowers that are reminiscent of peonies. However, the less common single and semi-double hollyhocks have bags more style and provide food for bees. The Halo series offers a wonderful range of colours and good disease resistance – ‘Halo White’ (white and yellow) and ‘Halo Cerise’ (magenta and purple) are two of the best. ‘Crème de Cassis’ is a charming old variety with blackcurrant and white blooms on two-metre stems. The dark-wine flowers of ‘Nigra’ and ‘Blacknight’ smoulder at the back of the border, seeming black from a distance. And ‘Mars Magic’ – a favourite of National Collection holder Jonathan Sheppard – is red. These are all forms of common hollyhock (Alcea rosea) that can be cultivated as short-lived perennials or, ideally, as biennials.

There are other Alcea species that look similar to common hollyhocks, offer more resistance to rust, and live for longer. A. ficifolia (a short-lived perennial) has the same funnel flowers, but bears attractive foliage reminiscent of fig leaves; A. rugosa, a perennial from Ukraine, has gorgeous primrose-yellow flowers; and the perennial Turkish hollyhock (A. pallida) carries lovely mauve-pink blooms on lofty stems.

Closely related to hollyhocks, the musk mallow (Malva moschata) is a scented native, producing either white or pink flowers that have an informal beauty. For creating naturalistic layers in borders, the fabulous palm-leaf marsh mallow (Althaea cannabina) has small pink blooms on tall, wiry stems, allowing you to glimpse the plants behind. And, last but definitely not least, × Alcalthaea suffrutescens ‘Parkrondell’ and ‘Parkallee’ are the wonderful must-try offspring of hollyhock and marsh mallow. All four are perennial and bloom in summer and early autumn.

Sow in spring under cover (for example, in a greenhouse) and plant out in summer, or sow in September under cover and plant out in spring. You could also sow direct, once the risk of frost has passed, in late April or May. Because garden-centre plants sometimes carry the fungal disease rust and because hollyhocks are so easy to grow from seed, it’s preferable to raise them yourself or buy plugs from a reputable supplier (such as The Botanic Nursery). Seedlings sown early in the year may flower the same year, whilst those sown later will bloom the following year.

Hollyhocks love sun, good drainage, and relatively poor soil. The seeds are big, so they are a good choice for growing with children and can be sown into module trays or individual pots of peat-free seed compost: one seed per module or pot. When they are ready to plant out, choose a sunny site and well-drained soil; do not add manure or other organic matter. Since they can grow very tall, it’s worth staking hollyhocks or growing them through supports to prevent wind damage once they surge towards the sky. In the right conditions, they will self-sow, providing you with new plants.

A lot of people like to sow hollyhocks in the narrow furrow of soil that sometimes runs between a wall and a path; if the seed takes, this is a glorious way of livening up a bare bit of wall. To prevent them leaning drunkenly into the path, you could tie a length of thick twine at each end of the wall.

Slugs and mice can nibble the leaves of young plants – therefore, provide protection (such as crushed shells and wire) upon first planting out. But the main problem hollyhocks face is the fungal disease Puccinia malvacearum, commonly known as hollyhock rust or mallow rust.

Rust puts a lot of people off growing hollyhocks, but it can be prevented. Grow them as biennials, rather than perennials, to stop the disease taking hold; this means discarding them once they have finished flowering. Ensure there is good airflow around the plants (for example, growing them in front of a fence is better than a wall); and always water the roots, never the leaves.

If hollyhocks develop rust, it first shows up as orange-brown spots and pustules on the leaves, and can eventually discolour all of the foliage. It is more likely to be aggressive during a wet summer. Remove and destroy affected leaves as soon as possible: for instance, on a bonfire.

Another way to avoid rust is to opt for plants that show some resistance to it. All described above, they include the hollyhock Halo series, fig-leaf hollyhocks (such as ‘Antwerp Mix’), Alcea rugosa, and A. pallida, as well as × Alcalthaea suffrutescens hybrids, all of which deliver the long-legged cottage-garden charm of hollyhocks, without the eyesore of browning leaves.

Traditionally grown against the sun-baked walls of a cottage garden or against the cottage itself, hollyhocks pair well with other plants that enjoy a sunny site and reach similar heady heights. Verbena bonariensis, Digitalis ferruginea, fennel, teasels, Allium ‘Summer Drummer’, and Allium ampeloprasum are tall enough to stand alongside hollyhocks at the back of the border; all have wildlife appeal and enjoy similar conditions to hollyhocks: relatively poor, well-drained soil in sunshine.