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Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree

In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight. Trees tend to be long-lived, some reaching several thousand years old. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees. Trees have been in existence for 370 million years. It is estimated that there are just over 3 trillion mature trees in the world.

A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development.

Trees usually reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead.

Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies.

Selected article

Krummholz or Krumholtz formation (German: krumm, "crooked, bent, twisted" and Holz, "wood") — also called Knieholz ("knee timber") — is a particular feature of subarctic and subalpine tree line landscapes. Continual exposure to fierce, freezing winds causes vegetation to become stunted and deformed. Under these conditions, trees can only survive where they are sheltered by rock formations or snow cover. As the lower portion of these trees continue to grow, the coverage becomes extremely dense near the ground.

Common trees showing Krumholtz formation include Balsam Fir, Red Spruce, Black Spruce, Subalpine Fir, Subalpine Larch, Engelmann Spruce, Limber Pine, and Lodgepole Pine. Instances of the Krumholtz form of Black Spruce, Picea mariana, are found in the northern Canadian Boreal forests. Krumholtz-form Black Spruce and Balsam Fir are abundant in the Alpine Transition Zone of the White Mountains of New Hampshire.

Selected biography

Krubsack pictured in 1919 sitting in the chair that he grew himself.

John Krubsack (1858-1941) was a banker and naturalist from Embarrass, Wisconsin. He conceived, planted and shaped living trees to create the first known grown chair. He started his chair in 1903 and harvested 11 years later in 1914.

In addition to banking, Krubsack was a prominent naturalist who farmed, made cheese, and landscaped his property long before these were common practice.[clarification needed] His house was the first in his region to have running water. He also was skilled at piecing together furniture from found branches. He’d scour the local river flats with a yardstick and a saw, looking for just the right shaped piece of blue beech, a hardwood tree with a smooth, wavy bark and a beautiful blue color when varnished. John took his youngest son, Hugo, on these weekend wood-hunting excursions, and it was during one of his trips that the idea first came to him to grow his own chair. Read more...

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Indian gooseberry, or Amla (Phyllanthus emblica)


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