We spied this Globe Thistle (Echinops ritro) in a garden in Phelps Grove Park in Springfield, Missouri. Widely considered a weed, it's actually prized by most gardeners for its airy, blue-lavender flowers and dramatic foliage and seedheads. It grows to 4 feet tall, thrives in sun or partial shade, and tolerates poor soils and drought. To prevent wild reseeding, remove flowers before they go to seed. The long tap root makes transplanting difficult unless plants are young. Globe Thistle blooms from June or July through September, butterflies love it, and it makes wonderful dried flowers.