GROWING HOLLYHOCKS

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THE BEST LOOKING RUST YOU’VE EVER SEEN…

Rust is the most common problem of hollyhocks; it is caused by a fungus (Puccinia malvacearum) that overwinters on contaminated leaves and stems. When conditions are favorable (i.e. cool and damp), small brown dots or pustules appear on the undersides of the new hollyhock leaves.  Spores of the fungus form in the pustules, and yellow-orange spots appear on the upper side of the hollyhock leaves.  As the spots enlarge, the center may fall out and cause pinholes to appear in the leaves.  Pustules may also appear on the stems, although the flowers themselves are not affected.

Although rust seldom kills a hollyhock, it weakens the plant considerably.  Once the rust is noticed on the upper side of the leaves, treatment can only keep it from spreading and will not cure the affected leaf.  Removal of the leaves which show signs of rust is the best way to keep rust from spreading. 

Early in the spring, preventive sprays of a fungicide can keep rust from infecting the plants.  Chemicals such as mancozeb or chlorothalonil (daconil) are effective, and organic control may be obtained by spraying with neem oil, sulphur, or copper.  The undersides of the leaves must be treated.  A weekly spray program should keep rust from infecting the hollyhocks.

At the end of the summer, all plant debris should be removed from the garden.  Do not compost these leaves and stems, as the spores will overwinter in the compost pile!

 Some gardeners believe that hollyhocks grown in a ‘lean’ soil of lower fertility are more immune to rust, and it is generally believed that a layer of mulch placed on top of the soil in spring will reduce the number of spores that make contact with the young plants. Morning watering of plants, without splashing the foliage, is another good cultural technique.

 Some types of hollyhock (Alcea ficifolia & Alcea rugosa) seem to be more resistant to rust than others, but most gardeners agree that keeping hollyhock debris removed is the best way to control rust.  Removal of mallow weeds from the vicinity of the hollyhocks will also help keep the disease from spreading to the hollyhocks. Good air circulation is important; plants which are too close together or those planted against a wall or solid fence are more prone to rust than those planted out in the open. Plants similar to hollyhocks but not members of the Alcea family, such as Sidalcea and Malva, are also less likely to be troubled by rust than hollyhocks are, and can give a comparable effect in the garden.

 Hollyhocks (Alcea rosea) are traditional favorites and are the backbone of many cottage gardens. There are varieties which range in height from 2’ to 8’ tall, so there’s an option for nearly every sunny garden! They are sun-loving plants and appreciate a well-drained soil.

Most hollyhocks are short-lived perennials; although they do not last more than a few years, they will self-seed and you can maintain their presence in your garden that way. The taller varieties will appreciate some protection in windy locations, although they generally do not require staking. They make an attractive backdrop to a perennial garden or against a wall. 

Most hollyhocks will not flower the first year if they are grown from seed. Be patient; the second year you will get lovely blooms! If you do not want your plants to self-seed, cut the flower stalks as the blossoms fade. Otherwise, allow the plants to go to seed and you will have more plants next year.

Two common maladies of hollyhocks are weevils and rust. Hollyhock weevils are grey and 1/8”-1/4” long (including snout!); they chew holes in both the leaves and the flower buds. They do not bother other plants, and can be controlled mechanically by tapping the plants after placing a cloth underneath them, and then dumping the weevils that drop off the plant into a bowl of water to which you have added a few drops of liquid dish soap. They may also be controlled organically by insecticidal soap or horticultural oil, or chemically by Sevin or Malathion.

Information on the reverse side of this sheet discusses ways to control rust. Neither rust nor weevils is a likely cause of death for hollyhocks, but both will make the plants look unattractive and will reduce their vigor.

Hollyhocks have been used by herbalists and enjoyed by gardeners since the 1500s. The plants are edible and the flowers have been turned into dolls by generations of little girls; hollyhock plants make a wonderful addition to a yard containing a fairy garden! As a general rule, deer do not bother hollyhocks.