Melissa officinalis L.
Lamiaceae (sin. Labiatae)
Origins and history
The genus name comes from the Greek word melissa (bee) because it attracts bees; the common name is due to its lemon-like scent. Also called common balm or balm mint.
Lemon balm leaves contain:
– essential oil (0.1 % of dry matter) containing geranial (35–40 %), neral (30-35 %), caryophyllene (8-10 %), citronellol, linalool;
– triterpene acids (ursolic acid, oleanolic acid, pomolic acid);
– polyphenolic acids (rosmarinic acid, chlorogenic acid, caffeic acid, ferulic acid, protocatechuic acid);
– flavonoids (luteolin, apigenin, isoquercitrin…);
– polysaccharides.The highest content of aromatic substances is during summer. Desiccation lowers the aromatic substance content.The essential oil is credited with sedative, spasmolytic, anti-inflammatory and antibacterial properties; polyphenolic substances and tannins with antiviral properties.
Used against catarrh, fever, influenza, flatulence, headache, toothache.
Used as carminative, diaphoretic (i.e. favors perspiration), sedative.
Diffusion and importance
About 50 hectares of lemon balm are cultivated in Italy, mainly in Piedmont, Tuscany, Lombardy and Marches, but there are small cultivations in other regions as well. France and Israel are among the main producers.
Products (leaves and essential oil) are mostly used in herbal medicine and the perfume industry.
Biologic type: perennial, rhizomatous, erect plant; when cultivated it can last 4-5 years (up to 10 years in exceptional circumstances).
Stem: erect, pubescent, with quadrangular section, branching, 50-90 cm high.
Leaves: ovate, opposite, dentate, with short stalks, with secretory trichomes.
Inflorescences: verticillate, at leaf axils, with white or rosy flowers. In Italy it blooms between June and August; plentiful nectar production.
Fruit: tetra-achene; 1000 achenes (“seeds”) weight 0.5-0.6 g; seed germination capacity: 3-4 years..
Climate and soil requirements
It prefers cool, humid climates and partial shade (direct exposure to the sun during the hottest hours is not advisable); it is sensitive to intense cold, dry environments and prolonged fog.
It prefers deep, fertile, medium-textured soil; adapts to heavy soil, provided there is no water stagnation.
Fundamentals of cultivation practices
It can be propagated through seed, rhizomes, plant division.
Sowing can be done directly in the field or in a seedbed for later transplanting. Direct sowing in the field is not practiced much as the germination percentage is low. Transplanting, the most common technique, is generally done in May.
Plant division can be done with 2/4-year-old plants in winter-spring; it is a rather expensive technique, so it is only done in small cultivations.
Planting is done in rows 50-60 cm apart, with plants 25-30 cm apart in each row, with a density of 10-12 plants/m2; low density is advisable as it promotes better development of basal leaves with better quality.
When ploughing, it is advisable to add manure to the soil (25 tons/ha); when planting, about 50 kg/ha of nitrogen, 100 kg/ha of phosphorus and 150 kg/ha of potassium should be spread; in successive years, at the start of vegetative regrowth, 50 kg/ha of nitrogen, 80 kg/ha of phosphorus, 100 kg/ha of potassium are used.
Irrigation is always necessary in our areas, especially after transplanting and harvesting to help the young plants take root. Water volume must be moderate, preferably done below the foliage to decrease the risk of root and leaf diseases.
Harvesting should only be done on sunny days, when the dew has dried.
For phytotherapeutic use, lemon balm is usually cut 2-3 times in the pre-flowering period (in the 1st year, only once; in successive years, twice – in June and September); to extract the essential oil through distillation, plants are harvested in full bloom.
Immediately after harvest, plants must be dried and/or distilled quickly because they are prone to fermentation and their essential oil is very volatile.
Yield is 8 to 12 tons/ha of fresh product, equal to about 5-6 tons/ha of dry product, but the quantity is considerably less during the first years. The essential oil is extracted through distillation with a yield of 4 to 20 kg per hectare.