Thymes are heliophylous plants and like the sun, a fact which reflects the ecology of the genus. Thymus plants frequently live on rocks or stones and it is very important that the soils are well drained. But different Thymus species require very different substrata, e.g.
T. carnosas lives on sand dunes near the sea (Figure 1.13), T. lacaitae on gypsaceous soils, and T. vulgaris usually on calcareous soils.
Thymes are very resistant plants, which allows them to live under extreme climatic conditions concerning temperature and water supply. They do not avoid either cold or aridness. Dense and tomentose hairs as well as acicular leaves enable some species to support very dry conditions. The high production of essential oils can also be an adaptive characteristic for dry climate, because the volatile substances evaporate and produce a saturated atmosphere around the plant that makes the loss of water more difficult. Especially some species of the section Serpyllum can live in very cold climate, like T. glacialis in Siberia or T. praecox in Greenland. From an ecological point of view we can find the following correlation: bushy, woody, and erect plants are widely distributed in dry climates, whereas in more fresh and humid climates usually plants with flat leaves and woody only at the base are more common. The latter usually are herbaceous with creeping or lying stems. Such species mostly belong to the sections Hyphodromi and Serpyllum. The production of essential oils in this group is probably lower than in the first one.
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