Hollyhock is the king species of sidewalk crack garden escapees. It is part of the Malvaceae family of plants, which includes some other incredible ornamental flowers: the Mallows, Rose of Sharon, Hibiscus and such. Most of the mallows are quite invasive, producing lots of little seedlings which can take over whole areas. The Hollyhock can easily grow to twelve feet tall and creates beautiful sprays of flowers. They are also edible.