Evergreen

As an evergreen is known in botany a plant that retains its leaves all year round. Here, the single sheet persists for at least 12 months. The counterpart are deciduous plants that lose all their leaves for part of the year.

The Journal durability in evergreen plants varies ( to be dropped shortly after the growth of new leaves the old leaves ) between just over a year up to a maximum of 45 years in the long-lived pine ( Pinus longaeva ). But species with a leaf shelf life of more than five years are rare.

A special case is the Welwitschia, an African nacktsamige plant that has only two leaves. This but continuously grow over the entire lifetime of the plant. The blade end dies and weathered respectively. The durability of a sheet piece in this case is between 20 and 40 years.

In warm tropical regions, most plants of the rainforest are evergreen. Replace their leaves little by little over the year, depending on age and fall like the leaves. Plants in climates with dry periods can be evergreen or deciduous. In warm temperate climates most of the plants are evergreen. In cold temperate climates less evergreen plants can be found, as few evergreen plants tolerate temperatures below -25 ° C. The most common evergreen plants in these areas are the conifers.

In areas where there is a reason for plants to be deciduous, it was because of a cold or dry season is to be evergreen usually an adaptation to low nutrient levels. Deciduous trees lose leaves with each release nutrients that they need to draw again from the ground during the formation of new leaves. If only few nutrients are available, evergreen plants have an advantage, even if their leaves or needles must resist cold or drought, and even if they can not operate as efficiently photosynthesis. In warm climates especially species such as pine or cypress can survive on poor soils. In the taiga or boreal forests, organic material decomposes slowly because of the cold. The nutrients from discarded leaves are thus not be quickly available. This also makes evergreen plants are preferred.

In temperate climates evergreen plants to promote itself: the discarded needles (or possibly leaves) of evergreen plants have a higher carbon-nitrogen ratio than deciduous trees. This leads to a more acidic soil and a lower nitrogen content. This makes it more difficult for deciduous trees to exist.