Lime tree (linden)

Lime, or linden (Tilia), is a long-lived deciduous tree that blooms at the start of summer and gives bees very good nectar. Its fragrant flowers are highly attractive to bees and other pollinators, and lime honey is made mainly in Central and Eastern Europe, where the tree has long been important for beekeeping. ¹⁴⁷

Species. Europe's most important lime is small-leaved lime (T. cordata), often growing with broad-leaved lime (T. platyphyllos); silver lime (T. tomentosa) and T. dasystyla occur in south-eastern Europe and around the Black Sea. ⁴ Small-leaved lime differs from the broad-leaved one by tufts of hairs in the vein axils on the underside of the leaf. ⁷ Many species and hybrids are planted as ornamentals, and in North America the genus is known as basswood. ¹²

The tree. Limes are tall trees that can live up to 500 years; small-leaved lime can survive more than 1000 years, even when coppiced. ⁴⁷ A lime first flowers at about 30 years of age, a solitary tree up to ten years earlier. Small-leaved lime grows up to 1500 m in the central Alps, its dormant shoots withstand frosts down to −34 °C, and it reaches north to Finland and Norway. ⁴⁷

Flowering and pollination. Limes bloom from the end of June to early July, and small-leaved lime flowers later than broad-leaved lime. The trees are pollinated by insects and are outcrossing; some trees in a population are self-sterile. ⁴ Bees collect both nectar and pollen from the flowers; Ohio State University describes lime as a rich summer nectar source. ²

Nectar, honeydew and yield. Besides nectar, lime can give honeydew when sap-sucking aphids such as Eucallipterus tiliae attack it, and this changes the colour and composition of the honey. ¹ In the Ukrainian forest-steppe a strong colony collects 15–17 kg of marketable honey from lime in a good flow. ³ Bast and honey were historically the main products of lime, which may have helped spread the tree in the Middle Ages. ⁴

Lime honey. It is light to medium in colour with a bright yellow tone, has a strong woody and fresh aroma, medium sweetness, slight astringency and a long aftertaste, and crystallises at a moderate rate. In 261 European samples it averaged 16.9 g water, 37.5 g fructose and 31.9 g glucose per 100 g. Its electrical conductivity is high for a nectar honey, and lime pollen is under-represented in it, sometimes strongly, because many planted varieties are sterile. ¹

Do lime trees kill bees? Dead bumblebees under silver lime have long been blamed on toxic mannose in the nectar. A 2017 review in Biology Letters found no experimental evidence that lime nectar is toxic: the bees most likely starve because the trees offer too little nectar late in their flowering. The authors advise planting other late-summer food sources in cities. ⁶

Lime flower tea. The European Medicines Agency lists dried lime flowers of T. cordata, T. platyphyllos and T. x vulgaris as a traditional herbal medicine to relieve symptoms of the common cold and mild mental stress. For adults the tea is 1.5 g in 150 ml of boiling water, two to four times a day; for colds it is not recommended under 4 years of age, and a doctor should be seen if symptoms last over a week. ⁵

Why it matters to you. Honey cannot tell lime species apart, so on the label simply look for lime or linden; a very light honey is pure nectar, a darker one may contain honeydew. ¹ If you plant trees in a city, add late-summer flowers next to silver limes to keep bumblebees fed. ⁶ Lime flower tea is a traditional remedy for colds, not a cure. ⁵