Marjoram is the name given to many species of perennial herb belonging to the genus Origanum
, including the major species Origanum majorana
which is grown for its leaves which are commonly used as a herb in cooking. Marjoram plants can be woody or herbaceous and possess multiple branching stems. The leaves are oval or round and are arranged alternately on the stems. The plants produce small pink, purple or white flowers and small oval, brown fruits and can reach up to 1 m (3.3 ft) in height. Marjoram is perennial and can be grown for 3–4 years but is commonly grown as an annual in northern climates. Marjoram may also be referred to as sweet marjoram and originated from the eastern part of the Mediterranean in Cyprus and southern Turkey.
The leaves of the marjoram plant are used fresh or dried as a herb in cooking. They may also be dried and used to extract essential oil which is used as a flavoring.
Marjoram is a temperate or subtropical plant and should be grown in full sunlight for best results. Marjoram will thrive in dry, rocky conditions which closely mimic their natural habitat. Plants will grow well in a rich, light loam with a pH range between 4.9–8.7. The optimum pH for marjoram is around 6.9. Marjoram is less hardy than its relative oregano and will grow best when the annual temperature does not fall below 15°C.
Marjoram can be propagated from seed, cuttings, layering or by dividing the root. The optimum method of vegetative propagation depends on the size and growth habit of the mother plant.
Seeds should be sown outdoors when the soil has warmed and all danger of frost has passed. Seeds can also be started indoors to produce transplants. Marjoram seeds should be sown indoors 6–8 weeks before planting outside. Sow seeds in a sterile seed starting mix in seed trays or pots 0.2–1.0 cm (0.08–0.4 in) deep and water gently. Ensure the temperature remains between 15.5 and 27°C (60–80°F). Seeds should germinate in about 5 days at 21°C (70°F). Due to the slow growing nature of the plant, many home growers choose to start with small plants which can be obtained from a nursery or garden center.
Sprawling marjoram varieties are easily layered by selecting a branch and covering with soil. A rock can be placed on top to hold the branch securely under the soil. The branch will develop it’s own root system and once established, can be cut from the mother plant and transplanted to a new site.
Larger, upright plants lend themselves to propagating from cuttings. Cuttings should be taken from approximately 20 cm (8 in) down the stem so that the basal portion of the cutting is hard and woody. The upper 5 cm (2 in) of the cutting can be nipped off to promote branching. Cuttings can be rooted in water, sand or a mixture of sand, peat and perlite.
Marjoram seedlings can be transplanted to the garden when they are between 6 and 8 weeks old, about 2 weeks after the last frost date. Plants should be spaced approximately 30 cm (12 in) apart, allowing 45 cm (18 in) between rows. Pinching back the growing tip of the plants after transplanting will encourage the growth of new shoots. Marjoram requires more moisture than oregano and soil moisture can be conserved by applying a layer of mulch around the plants.
General care and maintenance
Established marjoram plants are tolerant of drought but cannot tolerate water-logging. Established plants require additional irrigation only in very dry conditions. Marjoram planted outdoors requires minimum fertilization, particularly if planted in sandy or gravelly soils. In contrast, container grown plants require frequent addition of fertilizer. A half strength balanced fertilizer can be applied every two weeks if required. Marjoram plants should be pruned regularly to stimulate new growth. this pruning can simply be a method of harvesting from the plant but in the winter, any dead or damaged wood should be removed from the plant
Marjoram leaves can begin to be harvested any time after the plants have reached a height of 15–20 cm (6–8 in). Harvest leaves by pinching the leaves from the tips of the stems to encourage the more branching. Leaves should be pinched regularly to keep the plants productive and prevent them from going to seed. the best time to harvest marjoram leaves is just prior to flowering. Waiting or buds to form before harvesting will ensure the maximum essential oil content in the leaves.
Savio, Y & Robinson C. (1998). Marjoram, sweet marjoram, knot marjoram. In: Speciality and Minor Crop Handbook. University of California Division of Agriculture and Natural Resources. Available at: http://www.ctahr.hawaii.edu/sustainag...
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Meyers, M. (2005). Oregano and marjoram. The Herb Society of America. Available at: http://www.herbsociety.org/factsheets...
. [Accessed 18 February 15]. Free to access
Common Pests and Diseases
Spider mites (Two-spotted spider mite)
Leaves stippled with yellow; leaves may appear bronzed; webbing covering leaves; mites may be visible as tiny moving dots on the webs or underside of leaves, best viewed using a hand lens; usually not spotted until there are visible symptoms on the plant; leaves turn yellow and may drop from plant
In the home garden, spraying plants with a strong jet of water can help reduce buildup of spider mite populations; if mites become problematic apply insecticidal soap to plants; certain chemical insecticides may actually increase mite populations by killing off natural enemies and promoting mite reproduction
Small, dusty, bright orange, yellow or brown pustules on undersides of leaves; new shoots may be pale and distorted; large areas of leaf tissue die and leaves may drop from plant
Infected plants and rhizomes should be removed to prevent spread; heat treatment of roots may help to control the disease; roots should be immersed in hot water at 44°C (111°F) for 10 minutes, cooled using cool water and then planted as usual
Stems of young transplants or seedlings may be severed at soil line; if infection occurs later, irregular holes are eaten into the surface of fruits; larvae causing the damage are usually active at night and hide during the day in the soil at the base of the plants or in plant debris of toppled plant; larvae are 2.5–5.0 cm (1–2 in) in length; larvae may exhibit a variety of patterns and coloration but will usually curl up into a C-shape when disturbed
Remove all plant residue from soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans or a leguminous cover crop; plastic or foil collars fitted around plant stems to cover the bottom 3 inches above the soil line and extending a couple of inches into the soil can prevent larvae severing plants; hand-pick larvae after dark; spread diatomaceous earth around the base of the plants (this creates a sharp barrier that will cut the insects if they try and crawl over it); apply appropriate insecticides to infested areas of garden or field if not growing organically
Thrips (Western flower thrips)
If population is high leaves may be distorted; leaves are covered in coarse stippling and may appear silvery; leaves speckled with black feces; insect is small (1.5 mm) and slender and best viewed using a hand lens; adult thrips are pale yellow to light brown and the nymphs are smaller and lighter in color
Avoid planting next to onions, garlic or cereals where very large numbers of thrips can build up; use reflective mulches early in growing season to deter thrips; apply appropriate insecticide if thrips become problematic
Aphids (Peach aphid)
Small soft bodied insects on underside of leaves and/or stems of plant; usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants
If aphid population is limited to just a few leaves or shoots then the infestation can be pruned out to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver colored plastic can deter aphids from feeding on plants; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use