Herb of the Year 2005:
Oregano & Marjoram
The International Herb Association has designated the genus Origanum the
Herb of the Year 2005. Oregano and marjoram are common names for different species
within this genus, and there are several species in this genus in the mint
family (Lamiaceae).
There is some confusion about the names for the various species; the European
O. vulgare may be called Common Oregano, Wild Marjoram, or Pot Marjoram
depending on where you live; this plant has relatively little flavor. O. onites, from Greece and Crete, may also
be called Pot Marjoram or Greek or Cretan Oregano. Also known as Greek Oregano
is O. heracleoticum (also called O. vulgare subsp. hirtum, O. hirtum, or
O.
vulgare prismaticum), from Italy, the Balkan Peninsula, and West Asia, which is less hardy than
O. vulgare, but is much more flavorful. Another complication is that
different types of oregano readily hybridize. But in all of these plants,
essential oils, particularly
carvacrol, provide the distinctive oregano flavor. Sweet marjoram, O. majorana
from Asia Minor, is not winter hardy here and has a subtle taste unlike oregano
at all because it contains less carvacrol. Italian oregano (O. x majoricum) has
a bit of the sweet, perfumey scent of marjoram.
Several other unrelated plants with high amounts of carvacrol also have local
common names of oregano. "Mexican oregano" usually refers to a tall, tender plant
in the verbena family (Verbenaceae), Lippia graveolens, that
has a similar, but stronger oregano flavor, but may also refer to Poliomintha longiflora and Plectranthus amboinicus
(syn. Coleus aromaticus) in different parts of Mexico. P. anboinicus is
marketed as oregano in Puerto Rico, and Cuban oregano or Spanish Thyme in other
places. This Caribbean native is a large and thick-leafed plant that resembles a
succulent. In Spain Thymus nummularius is sold and used in place of
oregano.
Most plants in the genus Origanum are small perennial subshrubs or tender
perennials native to the Mediterranean and adjacent areas. In Wisconsin many of
the species are not completely hardy and are better grown as annuals or pot
plants. O.
vulgare has naturalized in the eastern United States. Oregano plants develop woody stems and can grow up to about 30" tall and
wide under optimal conditions, but most types remain at 8-12" high. Because of
its more compact habit, marjoram is often used in English knot gardens.
The leaves of Origanums are oval to spade shaped, dark green, and
many are somewhat fuzzy. Marjoram tends to be a more gray green color than
oregano, and the leaves are generally smaller and less fuzzy. The composition of
the oils, and therefore the flavor, of all of these plants is greatly influenced
by climate, moisture levels and soil. Flowers appear on long stalks in summer
and will last well into the fall. Oregano typically has pink flowers, while
marjoram usually has white blooms.
At
least one species of Origanum is used solely as an ornamental. Hopflower Oregano
(O. libanoticum) is a vigorous, trailing herb hardy to zone 4b. It can
grow 10-15" tall and spread 18-24 inches. It produces hop-like bracts of
lavender and chartreuse through the summer months; in autumn they turn brown and
dry. This plant looks best when cascading over a raised bed, rock garden or
container. Just like its culinary brethren, hopflower oregano needs well-drained
soil in full sun to thrive.
Varieties
Greek oregano is among the more common oreganos available in the U.S., having
‘true’ oregano flavor. It grows low to the ground, rooting as it grows outward.
It is a vigorous spreader, but not invasive. There are numerous named oreganos
offered for sale, but because of the confusion among names, it is not always
clear what plant you are really getting. Some varieties that are offered
include:
- Origanum 'Herrenhausen' has reddish-violet flowers.
- Origanum 'Hopley's Purple' has pungent, reddish leaves that can
be used either fresh or dried, but is used mainly as an ornamental.
- Origanum 'Santa Cruz' is an good choice for pots and planters.
- O. vulgare 'Compacta' doesn't get as large as other
types of oregano, but still produces quantities of dark green, fragrant
foliage.
- O. vulgaris 'Aureum' is a golden-leafed, ground cover type
used primarily as a landscape plant, such as for edging
paths or garden beds. It is edible with mild flavor.
Cultivation
Plants can be started from seeds, cuttings, or crown divisions. The very small seeds are
very small and should be started indoors. Barely cover the seeds with a
thin layer of sand or fine soil; they germinate better in light. Seeds should
germinate in 4-14 days, depending on temperature and light conditions. Transplanted
hardened-off seedlings to a permanent location when 2 to 3 inches high and
when the temperatures are expected to remain above 45°F. Space plants 12-15" apart in rows 18" wide.
However, "oregano" is quite variable when grown from seed (partly owing to the
confusion of names, but also to natural variation in carvacrol concentrations in
individual plants), so you may prefer to purchase a plant from a reputable
dealer. If you have a plant you like the smell or taste of, you can propagate it
by taking cuttings or root
divisions in the spring.
Oregano grows best in well-drained soil in full sun, while marjoram prefers
moister soil but still in bright light. As with most herbs, average to poor
soils produce the most concentrated flavors.
Pinch back any flower buds to keep the plants from getting rangy and going to
seed. Fertilize yearly with a balanced plant food. You may wish to mulch
plants to keep the foliage clean, but in our moist climate this invites root
rot. Oregano has few pests, but can become
infested with spider mites or aphids.
Harvest
You can start using the leaves, a
few sprigs at a time, once the shoots reach 4-5" tall until the first frost
(if outdoors) or all year long, if in pots inside. Essential oil levels are
highest just before the plant blooms, so the best time to harvest is just before
flowers begin to develop.
To harvest the entire plant, cut the stems down to the lowest two sets of leaves;
the plant should leaf out again within two weeks.
Tie in bunches and hang in a warm, dry, shaded place to dry. Once crisp, strip the
leaves from the stems and store in an airtight container.
Dried oregano leaves often are more flavorful than the fresh, because the
essential oils are more concentrated. Use twice the amount of the fresh herb as
you would the dried. But marjoram tends to be better when used fresh.
Uses
The leaves of oregano and marjoram are used for flavoring foods, and are best
added to hot dishes at the end of cooking to preserve the flavor and prevent
bitterness. They are an important component of commercially-produced
poultry-seasoning mixes.
Oregano is an essential flavoring in Italian cuisine, where its robust, pungent
flavor is great in tomato sauces, on vegetables and grilled meats, and, of
course, pizza. Other Mediterranean cuisines use less oregano, but it is of some
importance for Spanish, North African and Greek cooking.
Marjoram is more often used in recipes of French or English origin. Its sweeter,
milder flavor works in cheese, tomato, bean and egg dishes, salad dressings,
seafood sauces, and on poultry.
Oregano also has some medicinal and cosmetic uses, such as in bath oils and sachets to help relieve aches and stiff
joints. The dried flowers are used for fragrance in potpourris and perfumes.
– Susan Mahr, University of Wisconsin
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