Hollyhocks are one of the defining plants of the cottage garden: spires 5 to 9 feet tall of large crepe-paper flowers in white, cream, pink, apricot, red and near-black, single or double, with a silhouette recognisable from across the street. They are biennial or short-lived perennial, flowering most heavily in their second year, and they self-seed freely against walls and fences where they are happy.
Sow in late spring or early summer and set the plants out in fall, 18 to 24 inches apart in full sun and average to rich soil that drains; they tolerate clay and dry spells once established. In a windy spot stake them early. Cut the spent spike to the base and a plant often flowers again the following year. Rust, orange pustules under the leaves, is the one real problem; strip the lower leaves as it appears, water at the base, and start fresh plants from seed every couple of years rather than nursing old ones.
For cutting, take the spike when the lower third is open; individual flowers are short-lived but the spike lasts several days as the buds open. The stems are hollow, so fill them with water and plug the end with a thumb before plunging them into the vase. Bumblebees roll in the flowers, and the plant hosts the painted lady butterfly's caterpillars. Deer usually leave it alone; Japanese beetles do not.
Powdery mildew
White or grey powdery coating on leaves - usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.