poplar defined in 1944 yearpoplar - Poplar;
poplar - Genus: Populus L. Name from the Latin. (Salicacea.)
The poplars are an important genus, found right across the northern hemisphere - Europe, Japan, and North America, possessing the same general attributes throughout but varying widely in form and very prone to hybridise.
Amongst features common to all or most poplars are the oval leaf-buds placed spirally on long pliant twigs, often with ribs giving them an angular cross-section; these buds have several scales, a feature distinguishing all poplars from the closely allied willows. The exceptionally long leaf-stalks give the leaves their characteristic motion in the lightest breeze. The flowers of different sexes are always borne on different trees, in catkins, with only one flower to each catkin scale. The small seeds are always wind-borne by the aid of downy hairs. Fig. 1.
The genus Populus L. may be sub-divided into three sections. the trembling poplars have the leaf-stalks flattened sideways, which gives the leaves a more incessantly trembling motion than those of other poplars, since they have no lateral stability. The scales of their catkins are clothed in long hairs. Their young branches are slightly hairy, and their roots throw up many suckers. Except when aged, the bark of the trunk is smooth.
The most important of these is the white poplar (Populus alba L.) G. Silberpappel. The Abele Tree. Distinguished by its smooth pale grey or white bark, with a more rugged blackened base. Its leaves are variable in shape, oval or lobed, densely covered beneath with white down, and turn yellow in October.
The grey poplar (P. canescens Sm.) is similar, but has rounder leaves, light coloured, and smooth below, which catch the light with a remarkably pretty effect. Figs. 2g, 1, 3c, d, 4.
The aspen (P. tremula L.) G. Zitterpappel, Aspe; F. Tremble; W. Aethnen; E. Crann criteac, Eada, is a tree of altogether darker aspect. The smooth bark of the trunk is dark grey, and the dull green leaves are nearly round in shape with a sinuous outline, and smooth on both surfaces. Figs. 3b, 5.
These three Trembling Poplars are native to Britain, but local in distribution. The Grey and the White form large upstanding trees, 120 feet tall, 10 feet girth, but the Aspen seldom exceeds fifty feet in height.
The black poplars. These have a more rounded leaf-stalk, so that their leaves move less easily than those of the Trembling Poplars. Their catkin scales are risked, as are the twigs. The buds are often slightly sticky, and the bark rugged with vertical fissures.
The European black poplar (Populus nigra L.) G. Schwarzpappel; F. Peuplier; W. Poplysen, is indigenous throughout Europe, and occurs in a wild state in Britain. Its leaves are triangular or rhombic in outline, and the large branches make acute angles with the trunk.
It is best distinguished from allied species by the swellings occurring at intervals in its massive trunk. The leaves fade to a dull brown or black in autumn.
The variety pyramidalis is the well-known Lombardy Poplar, introduced from northern Italy, but probably originating in central Asia, distinguished solely by its erect habit of growth, all the branches being fastigiate, following the upward trend of the stem. The same habit of growth is found in varieties of the beech; elm, yew, and in certain cypresses. Fig. 6. A rather striking form, probably a hybrid, has the fastigiate habit for some 60 feet up from the ground, and then breaks out into the angular branching of the typical Black Poplar.
The Carolina black poplar (P. angulata Aiton) introduced from North America, is distinguished by larger buds, and ribbed twigs. Its leaves are in general larger than those of the common Black Poplar, triangular, and have the apex drawn out to a point. These leaves turn yellow before falling in autumn.
Hybrids between various species of Black Poplars are often extremely rapid in growth, one known as P. serotina, Hartig, is often planted to form a quick screen of trees. Figs. 7, 2J, 3a, 8.
The balsam poplars are distinguished by their sticky twigs and even stickier, delightfully scented buds. Their leaf-stalks are round, and the leaves more oval than those of other poplars.
The balsam poplar or Tacamahac, Populus balsamtfera L., introduced from eastern North America, and the extremely rapid growing Ontario Poplar (Populus candicans Ait.), are typical of this group. Their leaves, which open very early, are dark green above, cottony below. Allied forms occur in Oregon, Japan and Siberia.
The poplars flower in March or April, before the leaves appear. Each tree bears only male or female catkins. The male catkins are pendulous, 1 to 2 inches long, each flower consisting of nothing more than a mass of dull red stamens on a disc-like base in the axil of each catkin-scale. The female catkins are similar in appearance, but the disc Bears a single carpel topped by 4 red stigmas. Pollination is by wind.
The seeds ripen very early, being extremely small and numerous within the capsule which develops from each carpel, and clothed in white cottony hair to assist wind distribution. They fall in May, and unless they germinate almost at once, soon perish. As they usually fall each spring in large quantities, the female trees are unpopular /with gardeners, and it is usually the male tree which is supplied by the nursery trade. Poplars are seldom propagated by seed. The seedlings, with epigeal cotyledons, are very small, but make rapid growth in their first year.
Propagation by cuttings has the great advantage that trees of exactly the same strain as the parent are obtained - an important point when dealing with hybrids. In the case of poplars and willows, the same sex is also ensured. Almost any piece of poplar twig, set the right way up in normal nursery soil in spring, will take root and grow with great vigour. It is usual for nurserymen to keep a stock of named stools for the provision of cuttings as required. The Aspen, however, is best propagated by suckers, though its cuttings will take root in favourable circumstances.
Cuttings are normally planted out after one or two years growth. Owing to the rapid growth of the tree, and its light-demanding character, they are usually set far apart - 12 to 15 feet each way being usual.
In general, poplars demand a rich alluvial soil with abundant moving moisture. Stagnant water is fatal. They must have full sunlight and do not thrive in shade. For their size, they are remarkably wind-firm, and they have a high degree of resistance to frost. They are best planted on low-lying land with alluvial soil. Although most of the poplars are often planted in towns, few species are really happy there. The Carolina Black Poplar and its hybrids thrive the best under smoky conditions.
Poplars will coppice, but are not grown that way except to produce cuttings for planting or twigs for rough basket work. They may be pollarded - a useful way of keeping them in check in town areas.
On good soil, poplars grow with great rapidity to big dimensions, up to 130 feet in height and 18 feet in girth. Strong upward growth is a natural feature, even when open-grown.
Poplar wood is remarkable for its fight weight (28 lb. per cu. ft.). It is white or nearly so in colour and shows no distinct heart. ' Being soft and " woolly " in texture, its physical properties are not outstanding, and it is perishable out of doors; it is a poor fuelwood. As it has a high resistance to splitting, it is useful for floors of carts, lorries, or trucks exposed to the roughest usage. Its lightness and colour make it highly suitable for making chip baskets for fruit, in which peeled veneers are interwoven.
Aspen wood is of special value in the match industry, being white, light, and easily cut into small sticks.
In the past, poplars have been little cultivated in Britain under forest conditions, but given good soil and a sufficient degree of moisture, they may be expected to yield large volumes of timber on short rotations. The wood has distinct technical qualities for certain purposes, and could probably be utilised as veneer in plywoods.
Our fastest growing Poplar is P. generosa A. Henry, an artificial hybrid between P. angulata, a Black Poplar, and the giant Oregon Balsam Poplar, P. trichocarpa Torrey and Gray. This latter species has also given good results in British plantations. Hybrid Poplars indicate the great possibilities of scientific tree breeding.
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