Hardiness: Hardiness depends on the species or subspecies, though some are hardy to Zone 5. Most withstand a moderate freeze. In marginal areas, grow oregano as an annual or in containers that can overwinter indoors.
Soil preference: Culinary members of Origanum are easy-to-grow perennials that tolerate a variety of soils, as long as those soils are well drained. Like most Mediterranean-type herbs, they need only moderate water and grow best in a gravelly loam in full sun. If your soil retains too much moisture, grow oregano in raised beds or containers. Water. As easy as oregano is to grow, it has one definite dislike: too much moisture. Humidity, periods of excessive rain, or overwatering leads to root rot, which eventually kills the plant. To avoid it, amend your soil with plenty of organic matter to ensure better drainage. If too much humidity is a problem, encourage good air circulation by giving your plants plenty of room to spread.
Fertilizing: Oregano's fertilizer needs are minimal and often nonexistent, especially if you amend the soil with compost or other organic matter. Keep in mind that container-grown plants need to be watered and fertilized more often than plants grown in the ground. I usually fertilize my container herbs every 6 to 10 weeks during the growing season. Mulch. A stone mulch or light-colored gravel spread around the base of plants helps keep the soil surface dry.
You can begin harvesting oregano when the plant is about 8 inches high. The flavor is most intense just before the plant blooms. Frequent harvests will produce a bushier plant and keeps foliage succulent. In fact, it's a good idea to cut plants back to about 6 inches at least twice during the growing season, leaving ample growth in fall to sustain the plant through winter.
I've used both fresh and dried leaves in foods, and this is one herb that I usually prefer dried. Many chefs would agree. "Drying deepens the flavor and mellows it, so it's not as bitter," says Mark Carter, proprietor of the Carter House Inn and Restaurant 301 in Eureka, California. Cut oregano in the morning, after the dew has dried. Hang it in small bunches upside down, or lay it on screens in a warm, dry place. Once the oregano has dried (the leaves will be crisp), remove the leaves from the stems and store them, whole, in a glass container. To preserve the essential oils, wait until just before using them to chop or crush them.
Depending on the type of oregano, the flavor can be pretty strong, so start with a small amount—a little goes a long way. Taste as you go and add more if needed.
Each of the following eight types of oregano has its own distinctive flavor, from intensely spicy to subtle and sweet. Remember that anything labeled simply "Origanum vulgare" will most likely rate a culinary zero.
Cretan (O. onites). Tender perennial growing to 18 inches tall, with pale green to gray-green woolly rounded foliage. Also sold as pot marjoram or Turkish oregano. Strong, intensely spicy flavor. USDA Plant Hardiness Zone 8
Golden (O. vulgare 'Aureum'). Golden foliage adds pizzazz in the garden as well as the kitchen. Grows from 6 to 18 inches tall. Will tolerate shade, but leaves will be more chartreuse than golden if it's placed there. Mild oregano flavor. Zone 6
Greek (O. vulgare subsp. hirtum). Vigorous and very hardy. Grows to 3 feet tall with green, slightly hairy foliage. Greek oregano is generally best for most culinary uses, with 'Kaliteri' (a strain within the species) delivering the truest of oregano flavor (see below). Zone 5
'Hot & Spicy' (O. vulgare 'Hot & Spicy'). A potent cultivar of Greek oregano growing to 3 feet in height. As its name states, this one is hot and spicy. Zone 5
Italian (O. 5 majoricum). Also sold as Sicilian oregano or hardy sweet marjoram. Italian oregano is an exquisite blend of sweet and spicy, without the bitterness of more intense types. That characteristic flavor varies, however, as Italian oregano is a hybrid resulting from crossing sweet marjoram with oregano. Plant form, leaf size, and color can vary depending on the parents, but most plants are upright in growth to 2 feet tall, with small pale green to gray-green leaves. Wonderful fragrance and gourmet flavor. Zone 7
'Kaliteri' (O. vulgare 'Kaliteri'). This Greek strain is truly among the best (kaliteri means "the best" in Greek). Grows to 18 inches tall with silvery gray foliage. Spicy and flavorful without being too bitter. Zones 6 & 7
Khirgizstan (O. vulgare subsp. gracile, syn. O. tyttanthum). More ornamental than other types, with glossy green leaves and pink flowers. Bushy growth to 18 inches tall. Pungently spicy with true oregano flavor. Excellent container variety, with stems that spill over the edge. Zones 5 & 6
Syrian (O. syriacum; O. maru). Tender perennial, sometimes sold as Lebanese oregano. Variable in foliage color from pale green to gray, with larger leaves than Greek or Italian types. Grows 18 inches to 3 feet tall. Pungent oregano flavor similar to that of Greek. Zone 8
That spicy, robust oregano taste that's so synonymous with French and Italian cuisine doesn't come from just any plant labeled "oregano." This Mediterranean native belongs to the genus Origanum, which also includes sweet marjoram. But not all plants belonging to the Origanum family taste like oregano. Nurseries and garden centers often mistakenly sell a type of wild marjoram (Origanum vulgare) that has none of the spunk we expect from culinary oregano.