Hollyhocks: location, care & growing tips

When to plant hollyhocks? How do you propagate the flowers by seed and what should be considered when cutting? The best varieties and tips for hollyhock plant care.

In midsummer, the bee-friendly and towering hollyhocks bloom in many bright colours and decorate our balconies, house walls or garden fences with their large flowers. Contrary to what its name suggests, the hollyhock does not belong to the rose family (Rosaceae) at all, and it also has major visual differences from the species of the genus Rosa.

Hollyhocks: flowering period, origin and characteristics

Hollyhocks (Alcea) are flowering shrubs and form a distinct genus in the mallow family (Malvaceae). The ancient garden mallows originally come from the Orient. For a long time they have also felt at home in Europe. Their distinctive feature is their height. Hollyhocks can grow up to 3 m tall and are popular for planting in the back of herbaceous borders or even along house walls, which makes them stand out particularly well.

Hollyhocks are usually biennial, but in favorable locations may well be perennial. If they are reseeded annually, you can look at their beautiful flowers year after year. In the first year, only the rosette of leaves is formed, from which in the second year grows a sturdy, barely branched stem with numerous flower spikes. The stem and lobed leaves of hollyhocks, about 15 cm in size, are light green in colour and rough-haired. The flowering period of hollyhocks lasts from July to September. There is a great variety of hollyhocks species and cultivars, whose flowers appear in many different colours and can be unfilled or filled. Probably the best known and most common hollyhock species is the common hollyhock (Alcea rosea). It is also called garden mallow.

Tip: The hollyhock species Alcea rosea and Alcea ficifolia are biennials rather than perennials. In contrast, ficifolia hybrids of Alcea ficifolia and Alcea rosea (Alcea x ficifolia) are perennial rather than biennial.

Hollyhock varieties

Popular cultivars of the common hollyhock are Alcea rosea ′Nigra′ with deep red, almost black-looking flowers and Alcea rosea ′Pleniflora′, which is available in many bright colours such as yellow, dark pink or red and whose flowers are plump. Both cultivars grow about 2 to 2.5 m high.

A lesser known hollyhock species is Alcea pallida, also called Turkish hollyhock. It grows 1.8 to 2.5 m tall and has up to 10 cm large, wonderfully fragrant flowers in pastel pink. Its flowering period lasts from May to October, which is extremely long. This hollyhock is very low maintenance and resistant to drought as well as mallow rust.

Somewhat lower remain the cultivars ′Mars Magic′ and ′Polarstar′ from the Alcea rosea Spotlight series. They reach a height of growth of 1.6 to 1.8 m and form large cupped flowers in fire red or white with yellow centres. They have a special long-distance effect in the herbaceous border.

Tip: The flowers of double hollyhocks are less bee-friendly than the single flowers.

Planting hollyhocks

Hollyhocks can either be purchased from garden supply stores as pre-cultivated seedlings and then planted directly in the desired location in the garden, or they can be grown from seed. In addition to the correct timing of sowing, the choice of location plays an important role in the development of perennials.

When to plant hollyhocks?

Sowing hollyhock seeds can be from May or June. However, hollyhocks can be sown even into the autumn. Planting pre-pulled hollyhocks from the store can also be done from May. If the hollyhocks were grown from seed densely in a bed, they should be transplanted to their intended place in the garden or herbaceous border before the onset of winter, so that they can develop well next spring.

Where to plant hollyhocks?

Hollyhocks thrive in warm, sunny locations in the garden or on the balcony. They prefer a nutrient-rich and well-drained, dry to moderately moist soil. If the soil in your garden does not sufficiently meet these requirements, it is recommended to use a high-quality potting soil, such as our Plantura Organic Flower Compost. The location should also be as protected from the wind as possible, because the height of the stems of hollyhocks can easily break in the wind. Hollyhocks exposed to wind must be tied to a wooden stick or similar in time to prevent damage.

How to plant hollyhocks in flower beds

Hollyhock seeds can be sown on a loose, fine-crumb seedbed in the garden beginning in May and continuing into late summer. For better germination success on very sandy or even very heavy garden soils, the top layer of soil should be mixed with a seeding soil such as our Plantura Organic Herb & Seeding Compost.

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Then place 2 to 3 seeds at a time in small depressions 5 to 10 cm apart. Since hollyhocks are dark seedlings, the seeds must be covered with a layer of substrate about 2 cm thick. Within 2 to 3 weeks, the seeds germinate and gradually develop into vigorous seedlings. Now they need to be carefully dug up and replanted in the garden in the place designated for them. When doing this, make sure that there is a sufficient planting distance of 50 to 60 cm between the individual hollyhocks. In the first year, the young plants form only a rosette of leaves, from which in the second year grows up a stalk with numerous flowers.

Tip: Alternatively to preplanting the seedlings on a seedbed, the seeds can be sown directly into the flowerbed.

Planting hollyhocks in pots

Hollyhocks can also be well kept in a container on the balcony or terrace. Due to its slender, tall growth, the hollyhock mallow is very space-saving and therefore particularly suitable for smaller balconies. Hollyhocks form taproots, so when choosing a suitable planter, you should pay attention to sufficient height. In addition, the tub must have a drainage hole, as waterlogging should be avoided. Fill it with a suitable substrate such as our Plantura Organic Flower Compost. To increase the permeability of the substrate, you can add a little sand. Then, as described above, place 2 to 3 seeds at a time in small troughs about 50 cm apart and cover flat with substrate.

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Plant care

Hollyhocks are quite low maintenance and do not require any special care other than regular watering, occasional applications of fertilizer and pruning in autumn. In windy locations, tying to a wooden stick may be necessary to protect the stem from damage due to wind action.

Pruning hollyhocks

When the hollyhocks have faded, the stems should be cut back to about 10 cm above the ground. If you take pruning immediately after flowering, it may even lead to another flowering the following year. However, if one pursues the goal of seed production, cut the hollyhocks only after seed ripening.

Fertilising and watering

Especially in the first weeks after sowing, soil moisture as constant as possible is important for the seeds to germinate successfully. Young plants should also be watered regularly so that they can develop well. In summer, the soil around the hollyhocks must be kept at least minimally moist. By covering the soil with a light layer of mulch, you can keep moisture in the soil longer.

In the second year, hollyhocks are also happy to receive a spring fertiliser. For this purpose, for example, our Plantura Flower Food is very suitable. Alternatively, nutrient-rich organic compost can be used.

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Propagating hollyhocks

Hollyhocks multiply all by themselves if you wait until after the seeds have ripened before pruning the stems. The mature seeds fall to the ground and, under favourable conditions, germinate the same year or the following year and grow into new hollyhocks.

Sowing hollyhocks: propagation by seed

If you want to better control propagation, you can harvest the mature brown seeds in late summer and then selectively sow them as late as autumn or as late as early summer as described above. If the seeds are not to be sown immediately, it is important to dry them first and then store them in a dark container. This container should not be airtight, otherwise mold may occur.

Tip: Hollyhock seeds are often damaged by the long-nosed hollyhock shrew (a weevil). It drills holes in unopened flower buds and lays eggs inside. The seeds then contain larvae and are numb, thus unusable. Therefore, be sure to check the seeds for holes before storing them.

Are hollyhocks hardy?

The biennial hollyhocks are winter-hardy and do not require winter protection in our part of the world. The above-ground plant parts of hollyhocks die after flowering in the cold season and can be cut back. In very low temperatures, you can put a layer of leaves or fir branches over the hollyhocks as frost protection as a precaution. Especially for young plants, this measure is advisable.

Common pests and diseases

Especially too dense mallow is very often affected by a hollyhock disease called mallow rust. Mainly the hollyhock leaves are affected. Fungal infestation can be recognized by yellow spots and rust-red pustules on the leaf surfaces. As soon as an infested leaf is spotted, it should be immediately removed from the plant and disposed of in the residual waste to prevent further spread.

Another fungal disease of hollyhocks is wilt disease (Phoma). When attacked by the corresponding fungus hollyhocks begin to wilt from the bottom. The oldest leaves are attacked first and turn brownish at the leaf edges. The discolouration increases towards the centre and the affected areas turn black. Since these spots contain fungal spores that can spread to other plants, you should immediately dig up the plants completely and dispose of them in the residual waste, as well as replace the soil around the plant.

The following pests cause damage to hollyhocks:

• Long-weevil hollyhock weevil (Rhopalapion longirostre): weevil bores holes in flower buds and lays eggs inside; seeds later contain larvae and are useless.
• Mallow flea beetle (Podagrica fuscicornis): the beetle often occurs when the soil is too dry and bores holes, especially in the stems of hollyhocks; in these holes it lays its eggs, which hatch into larvae that subsequently eat plant tissue, damaging the plant.
• Especially in spring, aphids (Aphidina) and also snails appear more frequently, which suck the plant sap from the hollyhocks or leave feeding damage on them.

If you are interested in other bee-friendly plant species for your herbaceous border, you can find more ideas in our dedicated article on bee-friendly perennials.