The flower stalks on hollyhocks can reach heights of 9 feet tall! They can tower above a garden, adding a lovely vertical element to your yard. Hollyhocks need full sun to partial shade and moist, rich but well drained soil. The mistake many novice hollyhock growers make is to plant this flower in soil that is too dry. The foliage of Hollyhocks is susceptible to fungal diseases. To help reduce this, avoid overhead watering whenever possible and properly space plants to improve air circulation.