Greek oregano (Origanum vulgare subsp. hirtum) is the most intensely flavored culinary oregano available.
 
A compact, hardy perennial (zones 5–9) growing 12–18 inches tall, it forms dense mats of small, fuzzy, dark-green leaves on wiry stems and thrives in full sun and lean, well-drained soil with excellent drought tolerance.
 
In summer it produces clusters of white flowers loved by bees. This is the true oregano of Mediterranean cooking—sharp, pungent, and slightly bitter—with far higher essential oil content than common oregano, making it the preferred choice for chefs.  
 
Its oil is prized in herbal medicine for potent antibacterial, antifungal, and antioxidant effects, and it has long been used traditionally to ease coughs, colds, digestive upset, and minor infections.
 
Sold in a 2.5" pot.
 
Image via University of Illinois Extension.