From Academic Kids
- This article is about plant types. For other uses see Evergreen (disambiguation)
In botany, an evergreen plant is a plant which retains its leaves year-round, with each leaf persisting for more than 12 months. This contrasts with deciduous plants, which completely lose all their foliage for part of the year, becoming bare and leafless.
Leaf persistence in evergreen plants may vary from only just over a year (shedding the old leaves very soon after the new leaves appear), up to a maximum of about 40 years in Great Basin Bristlecone Pine (Pinus longaeva). However, very few species show leaf persistence of over 5 years.
One additional special case exists in Welwitschia, an African gymnosperm plant which produces only two leaves, which grow continuously throughout the plant's life but gradually wear away at the apex, giving about 20-40 years' persistence of leaf tissue.
In tropical regions, most rainforest plants are evergreen, replacing their leaves gradually throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous. Most warm temperate climate plants are also evergreen. In cool temperate climates, fewer plants are evergreen, with a predominance of conifers, as few evergreen broadleaf plants can tolerate severe cold below about -25°C.da:Stedsegrøn de:Evergreen pt:Folha persistente sk:Evergreen