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A crop of seeds is generally produced every year with a bumper crop often occurring every second year. A single tree between 5 and 20 cm (2.0 and 7.9 in) in diameter can produce between 12,000 and 91,000 seeds in a season. A tree 30 cm (0.98 ft) in diameter was shown to produce nearly a million seeds. [8]
The tree is found in open arid plains that usually receive less than 150 millimetres (5.9 in) of rain per annum. [6] They grow on shallow sand aprons overlaying gibber or clay slopes and plains and between longitudinal dunes or on alluvial flats between ephemeral watercourses. [4] The soils can be saline or contain high levels of gypsum. [9]
Two main opposing forces affect a tree's height; one pushes it upward while the other holds it down. By analyzing the interplay between these forces in coast redwoods (Sequoia sempervirens), a team of biologists led by George Koch of Northern Arizona University calculated the theoretical maximum tree height or the point at which opposing forces balance out and a tree stops growing.
They are evergreen or deciduous shrubs or trees growing to 1–18 m (3 + 1 ⁄ 2 –59 ft) in height and forming dense thickets. The largest, Tamarix aphylla, is an evergreen tree that can grow to 18 m (59 ft) tall. They usually grow on saline soils, [4] tolerating up to 15,000 ppm soluble salt, and can also tolerate alkaline conditions. [5]
A wild fig tree growing in Echo Caves near Ohrigstad, South Africa has roots going 120 m (400 ft) deep, giving it the deepest roots known of any tree. [115] El Drago Milenario , a tree of species Dracaena draco on Tenerife, Canary Islands , Spain , is reported to have 200-meter-long (660 ft) superficial roots.
Aspen trees are all native to cold regions with cool summers, in the north of the northern hemisphere, extending south at high-altitude areas such as mountains or high plains. They are all medium-sized deciduous trees reaching 15–30 m (50–100 ft) tall. In North America, the aspen is referred to as quaking aspen or trembling aspen because ...
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Platanus orientalis, the Oriental plane, [2] is a large, deciduous tree of the Platanaceae family, growing to 30 m (98 ft) or more, [3] and known for its longevity and spreading crown. In autumn its deep green leaves may change to blood red, amber, and yellow.