Poplars

What are they?

We have just two, native species of poplar and neither is especially common in our region, yet poplars are a frequent part of the landscape, thanks to their fast growth, liking for damp soils and their uses in the timber industry. Poplars - especially the fast-growing hybrids - have been planted en masse in damp river valleys where few other large trees will grow, as wind and shelter belts around orchards and croplands, and as screens to hide unsightly industrial buildings. These trees are members of the willow family and show a number of similarities to willows, including the presence of leaf stipules, wind-pollinated flowers arranged in petalless catkins and certain similarities in their twigs, buds and bark. The vast majority of poplars in our landscape are hybrids of horticultural origin and include some of the fastest growing of trees.

Where are they found?

Poplars are mostly of horticultural origin and have been largely planted into the landscape, so they can occur in a wide range of places. Some varieties are planted in plantation blocks on wet soils, while others will be found in stiff, straight rows along hedgelines and roadsides and can be very prominant in the landscape. Our two native species are mostly plants of damp river valleys but are also occasionally planted elsewhere on commons, greens and as amenity plants.

Identification

Some poplars are distinct and readily identifiable at all times, but many of the hybrids and their parents can be difficult to tell apart without several visits to gather details of buds, flowers and leaves. Most poplars can be quickly placed into one of three groups: the 'white' poplars with their diamond-studded bark, densely downy catkins and thick white hairs on their young growths; the 'black' poplars with their relatively small, rhomboid or deltoid leaves, and the hybrid poplars, with their balsam-scented buds and large, deltoid leaves with broad bases. A few others fall outside of these three groups, making them easier to identify by differences in leaf shape, particularly. Like willows, the poplars are dioicious, that is to say, male and female flowers are carried on separate trees. Species of poplar will have both male and female plants in the landscape, but named varieties will always be one sex or the other, so studying the catkins at flowering time can help. Note that male plants largely dominate in the landscape because female plants produce enormous amounts of wind-blown, fluffy seeds that are not popular with some people!

White Poplar Populus alba

Introduced from mainland Europe. Widespread, especially in urban situations, some parts of fenland and in coastal situations where it is planted due to its salt tolerance. Flowers late February to March with almost all plants being female. A tree to 28m with a broadly spreading crown when mature. Suckers freely, especially in coastal situations where the height is reduced by winds, to produce dense thickets. Leaves and first-year growth densely covered in persistent, white hairs; leaves of vigorous shoots and suckers are deeply lobed, like maple leaves. Bark pale, studded with dark, diamond-shaped marks; often craggy and deeply ridged at the base.


Habit	Female flowers	Female flowers	Crown leaves

Sucker leaves	Winter twig of young growth	Winter twig of older growth	Bark

Grey Poplar Populus x canescens

Introduced from mainland Europe. Widespread, especially in urban situations, some parts of fenland and in coastal situations where it is planted due to its salt tolerance. Flowers late February to March with almost all plants being male. A tree to 30m with a broadly spreading crown when mature. Suckers freely, especially in coastal situations where the height is reduced by winds, to produce dense thickets. Leaves and first-year growth densely covered in white hairs at first, but these hairs mostly drop off during the summer; leaves shallowly lobed, a little more deeply so on vigorous shoots and suckers. Bark pale, studded with dark, diamond-shaped marks; often craggy and deeply ridged at the base. A hybrid between White Poplar and Aspen but probably all trees are from commercial stock and were originally planted.


Male flowers	Male flowers	Crown leaves	Sucker leaves

Winter twig of older growth	Bark

European Aspen Populus tremula

Native. Widespread in damp woods, especially on heavy, clay soils, but also sometimes planted. Flowers late February to March, male or female. A tree to 30m with a rounded crown when mature. Suckers freely to produce open thickets. Leaves downy on opening but soon hairless; rounded in outline with waved margins and strongly flattened stalks, causing them to flutter in the wind. Young leaves are often strongly washed with purple, while sucker leaves are larger, more persistently hairy and a different shape to crown leaves, which sometimes causes confusion with other poplars. Bark grey, studded with darker diamond-shaped marks.


Male flowers	Male flowers	Female flowers	Crown Leaf

Spring leaves	Sucker leaves	Winter twig	Bark

American Aspen Populus tremuloides

Introduced from North America as an ornamental with an old record from south Suffolk. Flowers late February to March, male or female. A tree to 20m with a rounded crown when mature. Very similar to our native European Aspen but the leaf margins are more finely toothed.


Leaves	Leaves	Leaf margin

Winter bud	Bark

Black Poplar Populus nigra subsp. betulifolia

Native, but also widely planted. Widespread, especially on river flood plains, but rare as a mature, native tree and widely planted in the past. Flowers late March to April, most trees male with females being very rare. A tree to over 30m with fine branchlets and stout, spreading main branches which are often down swept. Young shoots and leaf stalks thinly hairy when first emerging in spring, but the hairs are soon lost. Leaves relatively small compared with those of the hybrid poplars. Trunk very craggy and, especially in older trees, adorned with large, rounded burrs with twiggy outgrowths.


Habit	Habit	Male flowers	Female flowers

Leaf	Winter twig	Winter twig	Bark

Lombardy Poplar Populus nigra subsp. nigra 'Italica'

Introduced and of horticultural origin. Occasional as a roadside tree, especially near houses, but most often seen as a windbreak or screen, planted in straight lines around sports fields or to hide industrial sites. Flowers March to April, always male. A tree to over 30m with a narrowly upright growth. Young shoots and leaf stalks hairless. Leaves relatively small compared with those of the hybrid poplars. Trunk relatively smooth.


Habit	Male flowers	Leaf	Leaf

Winter twig	Winter twig	Bark

Giant Lombardy Poplar Populus nigra subsp. nigra 'Gigantea'

(Female Lombardy Poplar) Introduced and of horticultural origin. The county floras list no records of this tree, but it can occasionally be found in parks, on roadsides or around farm buildings. Flowers March to April, always female. A tree to over 30m; when mature, trees are typically upright like Lombardy Poplar but broaden out at the top. Young shoots and leaf stalks hairless. Leaves relatively small compared with those of the hybrid poplars. Trunk relatively smooth.


Habit	Habit	Female flowers	Female flowers

Leaves	Winter twig	Winter twig	Bark

Hybrid Black Poplar 'Serotina' Populus x canadensis 'Serotina'

Introduced and of horticultural origin. Occasional as a roadside tree or around farm buildings. Flowers late April to May, always male. A tree to over 40m with a broad, unkempt look; major branches often extend outwards almost at right angles to the main trunk and the trunk often leans with age, making this an unsuitable tree for plantations. Young shoots and leaves are the latest of the poplars to emerge and are typically lightly copper-toned. Trunk deeply ridged.

This is one of many forms of the hybrid between the European Black Poplar (Populus nigra) and the North American Eastern Cottonwood (Populus deltoides), which are of horticultural origin and which are widely planted for timber production and for shelterbelts and windbreaks. Many such plants may be difficult or impossible to identify to variety and may need to be left simply as 'Hybrid Black Poplar'.


Habit	Leaves	Leaf	Leaf

Male flowers	Winter twig	Winter twig	Bark

Hybrid Black Poplar 'Regenerata' Populus x canadensis 'Regenerata'

(Railway Poplar) Introduced and of horticultural origin. Frequent as a roadside tree, as industrial shelterbelts and windbreaks or around farm buildings. Flowers April, always female. A tree to 30m with a broad, imposing look. Young shoots hairless. Leaves emerge mid-season and are typically lightly copper-toned at first but very soon turn green. Catkins typically are largely sterile and produce less fluff than other female varieties. Trunk deeply ridged.


Habit	Female flowers	Leaf

Seedhead	Winter twig	Winter twig	Bark

Hybrid Black Poplar 'Robusta' Populus x canadensis 'Robusta'

Introduced and of horticultural origin. Widespread as a roadside tree, as industrial shelterbelts and windbreaks or around farm buildings. Flowers April, always male. A tree to 40m with a broadly columnar and tidy look. Young shoots downy. Leaves emerge early-season and are typically the most richly copper-toned; leaves relatively large, deep green when mature. Trunk deeply ridged.


Male flowers	Spring leaves	Spring leaves	Leaf

Winter twig	Winter twig	Bark

Balsam Spire Poplar Populus x hastata

Introduced and of horticultural origin. Widespread and very common in roadside plantings and hedgerow shelterbelts and windbreaks. Flowers late March to April, female only and relatively short. A tree to 40m with a narrowly columnar look and no suckers. Young shoots slightly angular. Buds becoming sticky with yellowish sap that smells strongly of balsam. Leaves broader than those of most other poplars, green above and contrastingly whitish below and with a rounded base. Trunk typically rather smooth and showing dark, inverted 'V' marks at the branch bases.

Populus x hastata occurs as a natural hybrid in its native North America, but plants in cultivation in the UK are of horticultural origin. The usual form of the hybrid seen is a plant originally grown as Populus 'Tacatricho 32' (or shortened to TT32), a selected clone from a batch of hybrid seedlings. This was later marketed as Populus 'Balsam Spire' before being properly recognised taxonomically as being a selection of the hybrid between Eastern and Western Balsam Poplars.


Habit	Female flowers	Female flowers	Leaf

Leaves	Winter twig	Winter twig	Bark

Western Balsam Poplar Populus trichocarpa

Introduced from North America. Uncommon but found occasionally in roadside plantings and shelterbelts. Flowers late March to April, male or female. A tree to 35m with a columnar but often twiggy and untidy look. Young shoots hairless, sharply angular and ridged. Buds very elongate, becoming sticky with yellowish sap that smells strongly of balsam. Leaves narrower than those of other poplars, deep green above and contrastingly whitish below. Trunk relatively smooth but often partially hidden under twiggy burrs.


Habit	Leaf	Leaf	Leaf undersides

Winter twig	Winter twig	Winter twig	Bark

Eastern Balsam Poplar Populus balsamifera

Introduced from North America. Uncommon but found occasionally in roadside plantings and shelterbelts. Flowers late March to April, male or female. A tree to 35m with a variably narrow to broad crown. Young shoots hairless, sharply angular and ridged. Leaves broad and rounded, rather dark green above, much paler below. Whole tree balsam-scented, especially noticeable in spring as the buds burst.


Habit	Leaves	Leaves	Young leaves

Male flowers	Winter buds	Bark

Balm-of-Gilead Populus x jackii

Introduced and probably of horticultural origin. Uncommon but occasionally found as an ornamental or for screening. Flowers late March to early April, typically female and in lon catkins. A tree to 40m with an often irregular, scruffy look and freely suckering at the base. Young shoots rounded. Buds sticky with sap that smells strongly of balsam. Leaves broader than those of most other poplars, green above and slightly paler below and with a rounded base. Trunk typically rather smooth, but often obscured by twiggy side shoots. Most often planted as the variegated form 'Aurora' but trees often revert to green over time. Has become less popular over time as this hybrid is very prone to a canker that disfigures and often eventually kills the tree.


Habit	Female flowers	Spring growth	Leaf

Variegated form	Winter twig	Winter twig	Bark

Flora of East Anglia An Identification Guide

Poplars

What are they?

Where are they found?

Identification

Species List

Flora of East Anglia
An Identification Guide