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The PPQ works to safeguard agriculture and natural resources in the U.S. against the entry, establishment, and spread of animal and plant pests, and noxious weeds in order to help ensure the protection of native flora and an abundant, high-quality, and varied food supply.
Allée of pleached lime trees at Arley Hall. Pleaching or plashing (an early synonym) [4] was common in gardens from late medieval times to the early eighteenth century, to create shaded paths, or to create a living fence out of trees or shrubs. [1] Commonly deciduous trees were used by planting them in lines. The canopy was pruned into flat ...
Tree shaping (also known by several other alternative names) uses living trees and other woody plants as the medium to create structures and art. There are a few different methods [2] used by the various artists to shape their trees, which share a common heritage with other artistic horticultural and agricultural practices, such as pleaching, bonsai, espalier, and topiary, and employing some ...
Some trees may be rejuvenated by pollarding – for example, Bradford pear (Pyrus calleryana 'Bradford'), a flowering species that becomes brittle and top-heavy when older. [ citation needed ] Oaks, when very old, can form new trunks from the growth of pollard branches; that is, surviving branches which have split away from the main branch ...
The United States Forest Service (USFS) is an agency within the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands covering 193 million acres (780,000 km 2) of land. [5]
Hopkins' bioclimatic law states that in North America east of the Rockies, a 130-m (400-foot) increase in elevation, a 4° change in latitude North (444.48 km), or a 10° change in longitude East (two-thirds of a time zone) will cause a biological event to occur four days later in the spring or four days earlier in the fall. [1]
It is a large evergreen tree, attaining in favourable places a height of 21–28 metres (69–92 feet), and developing in open situations a huge head of densely leafy branches as much across, the terminal portions of the branches often pendulous in old trees. The tallest recorded, a tree planted at Windsor Great Park, is 30.4 m tall. [7]
Hedge laid in Midland style A hedge about three years after being re-laid. Hedgelaying (or hedge laying) is the process of partially cutting through and then bending the stems of a line of shrubs or small trees, near ground level, without breaking them, so as to encourage them to produce new growth from the base and create a living ‘stock proof fence’. [1]