Poplar - Populus: Planting, Growing and Care

Botany and description

The poplars belong to the Salicaceae family, just like the willows. The genus Populus includes 35 species distributed across the northern hemisphere. In addition to the species, humans have created a large number of hybrids and cultivars. Contrary to popular belief, the genus name Populus does not come from the Latin “populus” (people), but rather derives from the Greek “papalein” (trembling), referring to the characteristic trembling of poplar foliage.

The most common species of poplars are:

• Populus alba or White Poplar: this tree grows up to 25 m in height. The foliage has a whitish, downy underside. It tolerates drought, sea spray, and poor, calcareous soil;
• Populus X canescens: a hybrid between the White Poplar and the Aspen. The crown is rounded, and it can reach 30 m in height;
• Populus deltoides or Eastern Cottonwood: native to North America, this is a tough tree, but unfortunately short-lived and very brittle in strong winds;
• Populus fremontii: native to North America, it tolerates drought and extreme cold well;
• Populus lasiocarpa: a very attractive poplar with foliage veined in red and light green. It grows more slowly than its cousins and reaches only about 10 m in height;
• Populus maximowiczii: an Asian species whose young, downy shoots take on a beautiful red hue;
• Populus nigra or Black Poplar: a large poplar (30 m tall or more) with dark bark. Its cultivar ‘Italica’ (synonym ‘Pyramidalis’) is very famous and widely planted;
• Populus tremula or Aspen: a medium-sized poplar (15 m tall), but vigorous and very suckering. Its thin, flattened petioles make the foliage “tremble” at the slightest breeze;
• Populus tremoloides or Quaking Aspen: a North American poplar with finely toothed foliage that also trembles at the slightest breeze;
• Populus trichorpa or Balsam Poplar: a poplar native to the western United States. It tolerates sea spray very well. It is characterised by very fragrant young wood;
• Populus yunnanensis or Yunnan Poplar: native to Yunnan, it is a very beautiful poplar with reddish-veined foliage. It also resists heat and drought well.

Populus alba – Populus nigra – Populus tremulus

Populus alba – Populus nigra – Populus canescens

The cultivation of poplars is called poplar farming, and the foresters managing poplar plantations are poplar growers. A poplar plantation is called a poplar grove.

Poplars grow very quickly. These trees have therefore been widely planted along roads, canals, or as windbreaks. Poplars do not live very long: an average of 60 years. However, the Black Poplar (Populus nigra) can live for several hundred years. The rapid growth of poplars can sometimes be a drawback: the wood is soft and breaks easily in the wind. Never stay near a poplar during a storm! (and, if possible, avoid trees when it’s very windy!).

The root system of poplars is extensive, relatively shallow, but very spreading (like willows). It is therefore advisable to plant them far away (at least 30 m) from any buildings or structures, to avoid damage to pipes or foundations. Because the root system is shallow relative to the tree’s height, poplars can fall quickly during a storm. Two good reasons not to plant poplars near homes.

Poplars are large trees, sometimes over 30 m tall. Their habit can be columnar (Populus nigra var. italica) or pyramidal. The foliage is deciduous and features simple, alternate, cordate, triangular, or ovate and acuminate leaves (ending in a point). The leaves sometimes have a silvery underside. The leaves are attached by a long, flattened petiole. This flattening contributes to the trembling of the foliage. The foliage often turns bright yellow in autumn before falling.

Cottony down containing the seeds, which will be dispersed by the wind

When the tree is young, the bark is pale, almost white sometimes, becoming darker and more fissured with age. The wood is light and is used for making paper, matches, crates, plywood…

Like willows, poplars are dioecious species. This means there are distinct male and female individuals. The flowers appear as pendulous catkins in spring before the leaves. The male flowers are flexible with reddish stamens. The female catkins are stiffer. The pollen from the catkins is slightly allergenic for sensitive individuals.

The fruits follow the female catkins and form two-valved capsules containing cottony seeds. This cottony fluff allows the seeds to be carried by the wind or a watercourse. The cottony down from the seed capsules can also be allergenic.

The medicinal use of poplar is very ancient. The bark was used to combat fever. The buds and leaves were known for their diuretic and anti-rheumatic properties.

Poplars tolerate atmospheric pollution very well.

Our most beautiful varieties

Populus nigra Italica - Black Poplar

The famous Italian poplar is instantly recognisable by its very slender, dark silhouette and its almost columnar habit. This large deciduous tree, reaching 30m in height and 5m in spread, develops a vertical trunk extending to the crown's apex, supported by multiple fine, almost vertical branches.

• Flowering time April, May
• Height at maturity 30 m

See the product sheet

Populus tremula - Aspen

The Aspen is a large deciduous tree with very rapid growth, a fastigiate, light and elegant habit. Its foliage trembles (quivers) at the slightest breeze, revealing the silvery underside of its leaves.

• Flowering time June
• Height at maturity 20 m

See the product sheet

Populus alba Nivea - White Poplar

Populus alba 'Nivea', known as the White Poplar or Silver Poplar, is a robust medium-sized tree. The underside of mature leaves is downy, while young shoots and leaves are strikingly white, giving the tree a shimmering, silvery effect in the wind.

• Flowering time March, April
• Height at maturity 25 m

See the product sheet

Populus deltoides Purple Tower - Eastern Cottonwood

Populus deltoides 'Purple Tower' boasts remarkable foliage, transitioning from scarlet red to almost black violet-purple depending on the season, with contrasting blood-red main veins.

• Height at maturity 20 m

See the product sheet

Planting Poplars

Where to Plant?

The poplar is best planted in full sun.

Poplars thrive in deep, fertile soil, which is fairly moist to wet. The White Poplar (Populus alba) adapts to waterlogged or, conversely, dry soils, whether calcareous or poor. The Aspen Poplar tolerates sea spray well and can grow in sandy, poor soil.

When to Plant?

In pots: in spring or autumn.

Bare-rooted: between November and December.

How to Plant?

• Dig a large hole: approximately 1 metre wide and 60 cm deep;
• Loosen the bottom of the hole well and set aside the excavated soil;
• Soak the root ball if potted or dip the roots in slurry if bare-rooted;
• Place the tree in the centre of the hole;
• Refill the hole with the excavated soil and firm it well around the base;
• Water with 10 litres of water;
• Remember to stake the tree using three stakes arranged in a triangle.

Maintenance

Remember to provide a good watering can of water from time to time when the soil dries out during the first two years of cultivation. Additionally, a good mulch at the base of the tree will help keep the soil relatively moist.

Pruning involves removing dead, diseased, or poorly placed wood. Prune the branches of poplars in winter, outside frost periods and before the resumption of growth.

Poplars in autumn

Diseases and Pests

The new poplar cultivars are generally resistant to diseases, but some diseases can still occur.

Poplar Canker

Poplar canker mainly appears north of the Loire in spring or autumn. This disease is caused by a fungus, Xanthomonas populi. It thrives in warm and humid conditions. The disease first manifests as whitish, then brownish, sticky oozing at the base of the buds or lenticels. Cankerous lesions, forming irregular calluses, then appear on the branches.

There are no treatments available. However, you can choose cultivars known to be resistant to the disease. It is also advisable to prune only in winter and with tools thoroughly disinfected with alcohol.

Rust

The leaves are affected in spring when it is warm and humid: they discolour, then dry out and fall. The tree does not die but is weakened until new foliage appears.

→ For more information on rust and how to get rid of it, follow Pascal’s advice.

Honey Fungus (Armillaria mellea)

Honey fungus is a fungus that attacks weakened poplars. When symptoms become apparent, it is a sign of the tree’s relatively rapid death.

→ Read our advice sheet on honey fungus or root rot to learn more.

The Poplar Admiral Caterpillar (Limenitis populis)

This splendid butterfly was once considered a pest in poplar plantations. The caterpillar feeds on the foliage of the aspen poplar and other poplar species. However, this butterfly is in sharp decline and has practically disappeared in France and Belgium.

Multiplication

The poplar naturally produces suckers from its running roots. It also reseeds itself thanks to its multitude of seeds dispersed by the wind.

But the simplest way to propagate poplars remains propagation by cuttings from hardwood.

• In November-December, take cuttings from the tips of branches (or sections of stems) about 30 cm long;
• Plant them directly in the ground (the simplest method), or in a sand bed (moist sand) over winter until the cuttings develop roots;
• For those raised in a sand bed, transplant the cuttings into pots with compost in spring;
• Transplant them into the ground in autumn.

Poplar cuttings root so easily that poplar growers often plant poplar stakes, which are large stems of 1.50 m-2 m, about 20 to 30 mm in diameter. The lower end is trimmed at an angle, and the stakes are driven 80 cm into the soil at a rate of 200 young plants per hectare. A few years later, the poplar plantation takes shape.

Association

It is challenging to suggest companion planting ideas for such large trees as poplars. Typically, poplars are planted in rows, using the same essential oil repeatedly.

However, let’s take the example of the Populus deltoides ‘Purple Tower’, which could be coppiced every year. Its scarlet-red foliage, tinged with purple, will pair beautifully with other bushes and perennials whose foliage shares the same hues. Among bushes, a Physocarpus ‘Lady in Red’ and a Berberis thunbergii ‘Bagatelle’ would work perfectly. For perennials: a few Heuchera ‘Forever Red’ will thrive in the beneficial shade provided by the bushes and the poplar.

Too red-purple for your taste? No problem! In that case, opt for a strong green-yellow contrast to highlight the foliage of the poplar and other plants. For this role, the Catalpa bignonioides ‘Aurea’ will be ideal with its large green-yellow leaves. The size of its leaves will complement the foliage of the ‘Purple Tower’ poplar wonderfully. You can also coppice the Catalpa every year.

Populus deltoides ‘Purple Tower’, Catalpa bignonioides ‘Aurea’, Berberis ‘Bagatelle’, Heuchera ‘Forever Red’

Anecdotes

• France is the leading exporter of poplar wood and the second largest worldwide;
• It is said that Emperor Napoleon I introduced the Lombardy Poplar to France as a roadside or canal-side tree;
• For the druids, the poplar symbolised old age due to the silvery underside of its leaves;
• Ancient literature (Greek and Roman) regularly mentions poplars.