Citrus medica aka Lemon

Citrus medica, or citron, belongs to the rue family, Rutaceae. Kew places its native range from the Himalayas to Myanmar. Plants For A Future also lists Nepal, Assam and Bangladesh. Useful Tropical Plants says no truly wild plants are known. This evergreen shrub or small tree suits warm climates. People grow it for fruit and as an ornamental plant.

In gardens, citron grows about 8–13 feet [2.5–4 metres] tall. Its spread reaches about 5–8 feet [1.5–2.5 metres]. It has a loose shape, with spines on its branches. Its deep green leaves are oval and stay year-round. Plants can take 10–20 years to reach full size. Small flower clusters bear white blooms with pink outer surfaces. The flowers have a sweet scent. Yellow fruits follow, shaped much like large lemons. They can reach about 1 foot [0.3 metres] long.

Citron needs full sun and moist soil that drains well. RHS lists clay, loam and sand as suitable soils. It favours acid to neutral conditions and a sheltered site. In cooler places, grow it in a greenhouse or conservatory. Use loam-based, peat-free compost with grit added for drainage. Give strong light, but shade it from hot sun. Water well during spring and summer growth; reduce watering in winter. RHS also calls for daily misting during active growth. Use citrus feed through the year, following the product instructions. Its ratings are USDA zones 10–11 and UK H2. It tolerates cool conditions but cannot survive freezing.

The fruit is edible, though its flesh is very sour. Cooks use it more for flavour than for fresh eating. The thick rind goes into salads or becomes candied peel. That peel flavours cakes, puddings and sweets. Other uses include marmalade and liqueurs. Citron also has a long role in Jewish harvest rituals. Its scent has led to uses in perfume and rooms. Dried fruits have served as insect repellents among stored clothes. Several plant parts have uses in traditional medicine. These recorded uses do not establish safe or effective treatments.

Citron can provide a bold shape in courtyards and containers. Its leaves, scented flowers and large fruits add garden interest. RHS reports few disease issues, but lists several greenhouse pests. These include mites, scale insects, aphids, caterpillars and mealybugs. Useful Tropical Plants reports no known hazards. RHS gives a skin warning for lemon- and lime-bearing citrus. That warning concerns fruit contact, sunlight and skin allergy.