(Nepeta racemosa) 'Walker's Low'
Tall spikes of tiny blue or purple flowers that are best clumped together for a punch of color. 'Walker's Low' has fragrant lavender-blue flowers on 24-inch-tall stems that can grow to 3 feet wide; USDA Hardiness Zones
4 to 8. 'Blue Wonder' is more compact, with dark blue flowers; Zones 3 to 8.