Hollyhocks, or alcea, are colorful garden plants with long stalks that often reach up to eight feet high and produce flowers in white, pink, yellow, and crimson. Each stalk typically grows 7 to 12 flowers. Among the 60 species of hollyhocks, the alcea rosea, alcea pallida, alcea biennis, and alcea sulphurea are popular with home gardeners. Hollyhocks are biennials, which means they produce leaves in July and August of their first year and flowers the second year. To maintain healthy and vibrant plants, you'll need to grow fresh hollyhocks each year and maintain them well against pests and disease. Most hollyhocks survive from 2 to 3 years.
Plant the hollyhocks in front of walls, fences, and hedges. Arrange the plants at least 2 feet apart from each other. Avoid planting them too close to shrubs, however, as they will compete for the same nutrients in the soil. Because of their height, insert a stake 6 feet out of the ground to hold them upright as they grow. When the plant is half-grown, tie the stem to the stake with tar string to prevent it from falling over from the wind or rain.
Choose a location in your yard where the hollyhocks can receive full sunlight. If space is limited, hollyhocks can grow in some shade. Although they can thrive in moderate quality soil, hollyhocks prefer rich soil with good drainage. They do not thrive in cold damp soil, however, especially during winter months. Apply fertilizer to the soil in the spring. Give the plants plenty of water during the summer months and spread mulch or rotted manure around the plant. Don't let the soil get dry during the hottest months.
Examine plants periodically for infestation of cut worm and aphids. If pests are found, spray leaves with a mixture of one cup vegetable oil, one cup water, and two teaspoons dish soap immediately. Check plants for leaf spot, rust, and a fungus called Mallow fungus. For rust spots, apply green sulphur to the plant immediately. For disease and fungus, look for yellow or brown rust spots on the underside of the lower leaves. If left untreated, the disease will spread upwards. Eventually the leaves will develop orange and black spots and die. If you find diseased leaves, cut them off immediately. To prevent the spread of fungus, apply fungicide treatments in the spring when the leaves start to expand.
If planting from seeds, fill the trays during February and March to produce stalks in July and August. Store the tray in a cold area and shade if the outside temperatures are warm. As soon as leaves emerge in the trays, transplant them into small pots until they grow strong. In good conditions, existing hollyhocks reseed themselves and produce new plants each year without interference from the gardener. Remove lower flower blooms as they wither so as not to weaken the plant or inhibit the production of new seeds. When the plant stops flowering, cut down the stalk to about 1 foot high. Cover the stump with coal ashes to prevent slugs and snails.