Pohon poplar

Poplar, (genus Populus), genus sekitar 35 spesies pohon dalam keluarga willow (Salicaceae), asli dari Belahan Bumi Utara. Spesies poplar yang berasal dari Amerika Utara dibagi menjadi tiga kelompok longgar: pohon kapas, pohon aspen, dan pohon poplar balsam. Nama Populus mengacu pada fakta bahwa pohon sering ditanam di sekitar tempat-tempat pertemuan umum di zaman Romawi. Kayu poplar relatif lunak dan karenanya sebagian besar digunakan untuk membuat kotak kardus, krat, kertas, dan veneer.

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Deskripsi Fisik

Poplar adalah pohon yang tumbuh cepat tetapi relatif berumur pendek. Mereka tersebar luas di seluruh wilayah beriklim utara, mulai dari Amerika Utara hingga Eurasia dan Afrika utara. Daunnya bergantian dan berbentuk oval atau berbentuk hati, dengan margin bergigi halus (tepi daun). Daunnya bergetar karena angin, karena tangkai daunnya yang datar. Di Amerika Utara, aspens biasanya memiliki tunas tidak lengket dan kulit abu-ke-hijau halus, sedangkan kayu kapas dan poplar balsam memiliki tunas lengket dan kulit kayu yang lebih gelap dan sangat berkerut. Poplar adalah tanaman dioecious, yang berarti bunga jantan dan betina tumbuh di pohon yang terpisah. Bunga-bunga mekar di catkins terkulai (cluster bunga berkelamin tunggal) sebelum daun muncul, untuk memfasilitasi penyerbukan angin.Buahnya adalah kapsul berdinding tebal kecil yang mengandung banyak biji kecil yang dihiasi jumbai kapas dari rambut sutra. Benih sering dilepaskan dalam jumlah besar, dan rambut biji yang halus membantu penyebaran angin.

Common species

Two well-known poplar species of Eurasia are the white and black poplars. The white poplar (P. alba)—also known as silver poplar for its leaves, which have white felted undersides, and as maple leaf poplar for the leaves’ lobed margins—is widely spreading or columnar in form, reaching 30 metres (100 feet) in height. The gray poplar (P. ×canescens), a close relative of the white poplar, has deltoid (roughly triangular) leaves with woolly grayish undersides. The black poplar, or black cottonwood (P. nigra), has oval fine-toothed leaves, is long-trunked, and grows to a height of 35 metres (115 feet). Columnar black poplars are widely used in ornamental landscape plantings, particularly among the villas of Italy and elsewhere in southern Europe. White and black poplars are widely planted in the eastern United States and in Canada.

The balsam poplar, or tacamahac (P. balsamifera), which is native throughout northern North America in swampy soil, is distinguished by its aromatic resinous buds. The buds of the balm of Gilead poplar (P. ×jackii), which is similar, are used to make an ointment. The western balsam poplar, also called black cottonwood (P. trichocarpa), grows some 60 metres (195 feet) tall and is one of the largest deciduous trees of northwestern North America.

The common European aspen (P. tremula) and the American quaking, or trembling, aspen (P. tremuloides) are similar trees and reach a height of about 27 metres (90 feet). Quaking aspen is distinguished by its leaves, which have more-pointed tips, and spreads by rhizomes (underground stems). Clonal colonies of quaking aspen can grow quite large, and the most massive clonal organism on Earth is believed to be a forest of genetically identical trees, known as Pando, in Utah. The American big-tooth aspen (P. grandidentata) grows up to 18 metres (59 feet) and has larger, somewhat rounded, coarse-toothed leaves.

Cottonwood trees have distinctive deeply fissured bark and are exceptionally tolerant of flooding and erosion. Native to North America, the common, or eastern, cottonwood (P. deltoides) reaches nearly 30 metres (100 feet) tall and bears thick glossy leaves. The Fremont, or Alamo, cottonwood (P. fremontii) is the tallest of the cottonwoods and is found throughout southwestern North America.

Unrelated species

The tulip trees of the genus Liriodendron (family Magnoliaceae) are sometimes referred to as tulip, or yellow, poplars. Known for their showy flowers and distinctive leaves, the genus consists of two species, the Chinese tulip tree (L. chinense), native to China and Vietnam, and the American tulip tree (L. tulipifera), found throughout eastern North America.