Lemon Balm
A perennial and robust lemon balm, with bright green leaves and a citrus aroma, forming generous clumps.
About the variety. Vigorous and easy to care for, it grows from 70 to 150 cm and thrives in both full sun and partial shade; highly valued by bees.
Itinerário técnico
Um guia de cultivo passo a passo, da sementeira à colheita.
Sow in trays on the surface or barely covered, because the seed is small and needs light. Germination is slow and uneven, two to four weeks, at 18 °C to 22 °C. Do not drown the tray: moisten with a sprayer. Transplant at eight to ten centimetres and plant with the collar well at the surface, never buried, because that is where the plant rots. Sow in late winter or spring, in a sheltered tray, to plant out in the final spot after the frosts.
It wants cool, fertile soil with organic matter, at a pH between 6.5 and 7.5, and tolerates part shade. Unlike the Mediterranean herbs it grows better in moist soil than dry: in poor dry ground the leaf stays small and bitter. It is herbaceous and very hardy: it dies back to the ground in winter and resprouts in spring, even after hard frosts.
It grows well between 15 °C and 25 °C, in sun or part shade, and prefers cool soil to dry heat. It takes cold without any protection: the top dies back in winter and the root resprouts in spring. In a Mediterranean climate it is at its best in spring and autumn and appreciates shade over the middle of the day in summer. On the Portuguese coast it grows all year and humid air does not bother it. Inland in Portugal and Spain it needs watering and part shade in summer, or the leaf scorches and turns bitter. In France and Germany it is a trouble free outdoor perennial, winter included, with no protection at all. The same applies in Italy: easy across the whole country, with shade and water through the summer in the centre and south. It spreads by root and by seed: plant it where it can do no harm, or in a pot.
It asks for little and an over rich soil works against it. Soil that was composted for the previous crop is enough, with no extra feeding. Excess nitrogen gives soft, watery growth with little flavour and much greater sensitivity to pests and cold.
Water regularly, above all in summer: it likes soil that is always cool and moist. Lack of water is the commonest mistake with this plant: the leaf stays small and tough and loses its lemon scent. A straw mulch holds moisture and cuts watering.
Hoe often and always shallowly, because the roots are short, near the surface and break easily. The best method is to prepare the bed two or three weeks in advance, let the first flush of weeds germinate, remove it and only then sow: that gives you a decisive head start. A thin layer of sieved compost between the rows greatly reduces later work.
Pests are few because the plant's aroma keeps many insects away. Aphids are the commonest problem and gather on the soft shoots, above all on over fed plants: cut off the affected tips and apply potassium soap. Red spider mite appears in dry heat and in pots, and is checked by wetting the foliage in the morning. Slugs and snails devastate seedlings: protect with an ash barrier in the first weeks. Thrips and leafhoppers are occasional and rarely need action.
The disease that actually kills these plants is root and collar rot from excess moisture, above all in a wet winter on heavy soil. There is no treatment: only prevention, through drainage, shallow planting and a handful of coarse sand or gravel around the collar. Powdery mildew can appear on crowded plants and is solved by opening them up with pruning.
Harvest by cutting whole stems a few centimetres above the ground: the clump regrows strongly and gives two or three cuts a year. Aroma is most concentrated just before flowering, in the morning once the dew has dried. In late autumn cut everything down to the ground, and every three years divide the clump in spring. The reference colour is green, and that is what tells you it is ready.
