Creeping thyme (Thymus serpyllum), USDA zones 4-8. This is a plant that does well in full sun, so place it in a hot, sunny path. Like the thyme you're used to using in cooking, it has rounded leaves and a wonderful fragrance. But unlike its counterpart, creeping thyme grows nice and low to the ground (usually not more than 2 centimeters tall), and is extremely tough. It will grow in very difficult soils and can handle inconsistent watering.