There are over 60 different species of hollyhock (Alcea). While the common hollyhock (Alcea Rosea) is the most well-known and cultivated species, others would look just as at home in a traditional cottage garden setting. Most are tall, pretty, perennial or biennial flowering plants that grow to reach as much as 8 feet tall. Their height and large blooms make them ideal candidates for adding to the back of borders or growing up against walls or fences. They easily self-seed, so you will have beautiful, long-lasting blooms every summer.
While the double-flowering varieties look impressive, stick with single-flowering varieties if you want to attract pollinators like bees.
|Botanical Name||Alcea spp.|
|Plant Type||Herbaceous, Perennial, Biennial|
|Mature Size||Typically up to 8 ft. tall, 1-2 ft. wide|
|Sun Exposure||Full sun, Partial shade|
|Soil Type||Moist, Well-drained|
|Soil pH||Acid, Neutral, Alkaline|
|Flower Color||Various including White, Pink, Red, Yellow, Lavender|
|Hardiness Zones||2-10, USA|
|Native Area||Asia, Europe|
Although there is variation in care requirements across hollyhock species, most are known for being adaptable and relatively cold-hardy plants that can be grown in many U.S. regions. Pick sites sheltered from the wind to prevent these tall plants from flopping and space individual plants far enough apart to promote good air circulation—most hollyhocks are susceptible to the moisture-loving fungal disease rust. Positioning them anywhere from 18 to 24 inches apart is best.
Most hollyhocks can survive in partial shade, but they generally prefer a full sun position. These tall plants can flop in overly shady locations. If you live in a particularly hot and dry region, a partial shade location will prevent the lower leaves on your hollyhock from withering.
Hollyhocks are versatile plants, and most can grow in any soil type. Rich, well-drained soils can produce the best results, but amending with organic matter is often all that is needed to boost your plants in poor quality, infertile conditions. This will also promote better air circulation and drainage.
Seedlings and young hollyhocks prefer consistently moist conditions—aim to keep the top 5 inches of soil damp. Soggy conditions, however, are a problem, particularly in the winter. Once established, your hollyhocks may only need watering when you experience prolonged hot and dry spells.
Water hollyhocks at the roots and not on their leaves to help prevent problems with the fungal disease rust.
Temperature and Humidity
These plants are best grown in temperate regions. They are reasonably cold-hardy, and some species can survive in temperatures as low as 0 degrees Fahrenheit, but early fall frosts can damage late blooms. These plants don't like high humidity because of their susceptibility to rust.
Hollyhocks are fans of fertile conditions and do best with high levels of nutrients in the soil. Without this, you may notice yellowing foliage and less impressive blooms. If your soil isn't rich, amending with organic matter during the spring is beneficial. Fertilizing isn't necessary in fertile soils, but in poor soils feeding every two to four weeks during the bloom period can also help. An organic flower fertilizer or a fish emulsion that is high in nitrogen works well.
Types of Hollyhock
The most common species of hollyhock found in gardens is Alcea rosea, known as the common hollyhock. Many cultivars of this species are available, with some being more rust-resistant, taller, or cold-hardy than others.
Some species and cultivars to look out for include:
- The bristly hollyhock (Alcea setosa): Flowering earlier than the common hollyhock, this species typically blooms from April to June, grows in USA hardiness zones 5 to 9, and the blooms are pink.
- The Russian hollyhock (Alcea rugosa): Not as cold-hardy as the common hollyhock, this yellow single-flower species is resistant to hollyhock rust.
- Alcea rosea 'Chater's Double': A common hollyhock cultivar, this beautiful double-flowered variety comes in many shades and blooms right through the summer.
- Alcea rosea 'Blacknight': A striking single to semi-double flower almost black hollyhock. This cultivar is a true perennial rather than a biennial variety.
Because these plants grow easily from seed, most gardeners stick with this method. However, you can also propagate hollyhocks by division in the spring or fall (outside of the bloom time) or from basal cuttings any time of the year, providing you select rust-free plants.
How to Grow Hollyhocks From Seed
Hollyhocks readily self-seed and, if you already have them in your garden, new plants will likely pop up the following year without any effort on your part. If you want to introduce them to your garden, growing them from seed isn't difficult. Follow these general tips for a more successful germination rate, but always check temperature and timing specifics for each species or cultivar:
- Sow seeds indoors during the second half of spring or in early summer outdoors
- Ideal temperatures for germination are usually around 60 to 70 degrees Fahrenheit
- If you sow seeds in the fall, you can overwinter them in a cold frame or greenhouse and they should flower the following year
- Hollyhocks typically take around two weeks to germinate.
Common Pests & Plant Diseases
The main problem for hollyhock species is the fast-spreading fungal disease rust. This affects the plant's foliage and can cause leaf drop and damage, discoloration, and stunted growth.
Water carefully, space plants appropriately, and remove the leaves on the lower part of the stem to minimize problems. Cutting back the plants after their bloom period in the fall and removing any plant debris or infected plants can also help to prevent spread.
How to Get Hollyhocks to Bloom
The size and appearance of your hollyhock flowers will depend on the species you select. They are typically large (often around 5 inches in diameter), outward-facing, and on a long central stem. They come in a wide variety of bright colors and are known for their long-lasting bloom period—which often runs from early summer through to the fall.
To make the most of the bloom period and to encourage large, healthy flowers, make sure your hollyhocks get enough nutrients and that you deadhead spent flowers and provide consistent moisture while establishing.
Are hollyhocks easy to grow?
Hollyhocks are low-maintenance and easy to grow. They just need fertile soil, plenty of sun, and appropriate spacing and moisture levels to prevent problems with the fungal disease rust.
How long will my hollyhocks last?
Even though these short-lived perennial species are often grown as biennials (only producing blooms in their second year before dying off), you should enjoy prolific new blooms every year because they self-seed so readily.
Do hollyhocks make good cut flowers?
Tall hollyhocks are perfect for adding height and floral interest in a cut flower vase. They typically last a week to ten days once cut.