POPULUS: CHARACTERISTICS, HABITAT, SPECIES, CULTIVATION - BIOLOGY - 2025

Populus is a genus made up of a group of tall deciduous trees belonging to the Salicaceae family. Commonly known as poplars or poplars, they comprise an approximate group of 40 species native to the temperate regions of the northern hemisphere.

They are fast-growing trees, with a closed and oval crown, petiolate, simple and alternate leaves of variable shapes and sizes, with a smooth upper surface and a tomentose underside. The apétalas flowers are grouped in hanging catkins, the male dense, short and reddish, the female loose, long and greenish. The fruit is a dehiscent capsule.

Populus nigra. Source: WeeJeeVee / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Its natural habitat is located on the margin of water courses or springs in areas with an altitude lower than 1,200 meters above sea level, where it forms extensive gallery forests. It is cultivated commercially for forestry and as an ornamental plant, also used as a living fence, to provide shade and protection from strong winds.

The most popular species are the black poplar or poplar (Populus nigra), as well as the quaking or aspen (Populus tremula), which grows up to 2,000 meters above sea level. The white poplar or white poplar (Populus alba) is common throughout the Iberian Peninsula, it adapts better to warm environments, but it does not develop above 1,200 meters above sea level.

General characteristics

Appearance

Fast growing deciduous trees that can reach, depending on the species, between 10 and 40 m in height. They present flexible and vigorous branches that develop a wide and dense crown of oval or irregular shape, the buds are coniform, sharp, pasty and reddish.

The trunk is usually straight, but with age it takes on a sinuous appearance, the bark is smooth and greyish when young, fissured and brownish in adult specimens. The branches develop from the lower part, the main ones broad and vigorous, the branches flexible, slightly angular and with yellowish or greenish tones.

Leaves

The simple, alternate and deciduous leaves are regularly broad, oval, heart-shaped, deltoid or rhomboid, the margins entire, toothed, scalloped or lobed. Petiole compressed 2-6 cm long, glabrous and dark-green on the upper surface, tomentose and light green on the underside, 5-8 cm long. During the fall the leaves turn yellowish.

flowers

In general, poplars are dioecious species, with female feet and male feet, or monoecious with female and male flowers on the same foot. The small flowers that lack petals and sepals are arranged in pendulous inflorescences or catkins a few centimeters long.

The scattered green female catkins are 7-15 cm in length, the dense, reddish male catkins are 4-9 cm in length. Flowering occurs at the beginning of spring, before the leaves develop, pollination is anemophilic.

Male Canadian Poplar Catkins. Source: pixabay.com

Fruit

The fruit is a greenish dehiscent capsule that is grouped into small clusters that open into 2 valves when ripe. They tend to ripen during the summer when they take on a brownish color and release numerous seeds covered with a white vilano, which gives them the appearance of a flake.

Taxonomy

- Kingdom: Plantae

- Division: Magnoliophyta

- Class: Magnoliopsida

- Order: Malpighiales

- Family: Salicaceae

- Genus: Populus L.

Sections

- Sec. Aegiros

- Sec. Leucoids

- Sec. Populus

- Sec. Tacamahaca

- Sec. Turanga

Etymology

- Populus: the name of the genus derives from the Latin «popŭlus» which means «popular», as they are very abundant trees in their natural habitat.

Habitat and distribution

Most species of the genus Populus are native to the temperate zones of the northern hemisphere. Nowadays it grows wild throughout Europe, parts of Asia, North Africa and North America, some varieties have even been introduced in the southern hemisphere.

It develops in very humid environments, on the fringes of streams, riverside forests, cultivated fields or land removed from embankments. They are very avid trees for water, so they are frequent along surface streams, underground courses or deep water tables.

Populus tremula female catkins. Source: pixabay.com

Featured species of the genus

Among the main species of the genus Populus, we can mention: Populus alba (white poplar), Populus x canadensis (Canadian poplar) and Populus canescens (gray poplar). Also, Populus deltoides (North American black poplar), Populus lasiocarpa, Populus nigra (black poplar), Populus tacamacha (balsam poplar) and Populus tremula (aspen).

Populus alba

Known as poplar, white poplar or poplar, it is a native species of the Iberian Peninsula, it is distributed by northern Africa, Western Asia and south-central Europe. It is a deciduous tree with an erect or sinuous trunk, with a greenish-white bark when young, reaching up to 25 m in height.

The older specimens have cracked and dark bark, branches and underside of the leaves covered by dense whitish hair. It is a dioecious species whose flowers are grouped in hanging catkins, the male reddish and the female green, the fruit is a hairy capsule.

Populus angustifolia

Populus alba or white poplar. Source: pixabay.com

Known as narrow poplar or willow-leaf poplar, it is a deciduous tree native to the western United States, characteristic of the Rocky Mountains. It is a tree with a slender profile that reaches 30 m in height, lanceolate leaves with scalloped margins and a yellow-green color, hairy and whitish catkins.

Populus

Known as poplar, it is a species widely distributed throughout Spain, on the banks of its rivers, particularly in the Duero and Ebro rivers. Deciduous tree with partially smooth bark and grayish-brown color, with glabrous branches when young, reaching a height 30 m.

Deltoid leaves with finely toothed margins have a long triangular petiole with two small warts at the junction with the blade. The inflorescences are grouped in hanging catkins of reddish or greenish tones.

Populus nigra

Known as poplar, poplar, negrillo or pobo, it is a native species of Eurasia, widely distributed in the Iberian Peninsula on very humid soils. Deciduous tree with fissured bark formed by very dark longitudinal plates and a pyramidal crown that reaches 30 m in height.

The long-petiolate rhomboidal leaves have finely rounded margins, being glabrous on the upper surface and tomentose on the underside. The flowers are grouped in slightly tomentose hanging catkins, the male reddish and the female greenish.

Populus tremula

Populus tremula. Source: pixabay.com

Known as quaking poplar, trembling or trembling, it is a species that is distributed from Europe to Asia, including the Algerian Atlas. Deciduous tree with smooth bark and grayish-green color, completely glabrous terminal branches and curved crown, reaching 30 m in height.

The oval and petiolate leaves show the margins with small shallow lobes, green limbs, smooth on both sides. The flowers are grouped in very hairy pendulous inflorescences, the male ones large and red, the female ones small and green. The seeds have tomentum.

Culture

Bark of Populus nigra. Source: Димитър Найденов / Dimìtar Nàydenov / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Trees of the genus Populus require soils with a loamy-sandy texture, fertile, loose and humid, with preferences in easily flooded soils. It can develop in dry and compact soils, but its vigor and growth rate is lower.

It requires full sun exposure, tolerates low temperatures and is not demanding in terms of soil pH levels, as long as it does not reach extreme ranges. Most are tall and fast growing species that do not reach ages above 100 years.

Its propagation is carried out naturally through seeds or through root suckers or suckers. Also, robust plants can be obtained from cuttings of stem or root fragments, washed away by floods and rooted in high humidity environments.

Commercially, the best form of propagation is through cuttings or cuttings obtained from healthy and vigorous plants. Vegetative propagation constitutes for this genus a form of adaptation to its environment, where it requires an effective method of multiplication.

Care

- Poplar trees require full sun exposure and good lighting throughout the day. In fact, they are very resistant to winter cold.

- Their edaphic requirements are minimal, although they prefer soils with a high content of organic matter and good moisture retention capacity.

- They are cultivated as soil fixing species near water courses, canals or hydraulic sites. Due to their deep and extensive root system, they must be located as far away from buildings, pipes and asphalt roads.

- They require high availability of humidity all year round, it is special during the hot summer months.

- It is convenient to make an amendment with mineral or chemical fertilizers at the time of planting and apply organic fertilizers at the beginning of spring.

- Usually does not require maintenance pruning, only the removal of dry or diseased branches.

Diseases and pests

Diseases

- Bacterial poplar canker (Brenneria populi): symptoms are manifested as darkening of the branches and trunk, accompanied by an exudation with an internal lesion. Its presence causes the general weakening of the plant, defoliation and terminal death.

- Spring defoliation (Venturia populina): symptoms are manifested with the drying and blackening of the leaves, petioles and twigs, general wilting and defoliation. Defoliation begins in the upper part of the crown and rapidly covers the entire tree, the damage is similar to that caused by late frosts.

- Marsonina (Marssonina brunnea): fungus that affects the lower leaves, causes brown spots with a lighter center. In general, premature defoliation occurs, in the same way it delays the foliation of the next year and in severe attacks it causes the death of the plant.

- Poplar rust (Melampsora larici-populina): symptoms appear as orange spots on the underside of the leaves, brown spots are observed on the upper surface. This damage causes early leaf fall, slow growth, poor lignification, decreased accumulation of reserves, and general weakening.

Illustration of Populus nigra. Source: Amédée Masclef / Public domain

Pests

- Poplar-boring weevil (Cryptorhynchus lapathi): it is a curculionid whose larvae build galleries that cause damage to young and adult plants. This weevil is a pest of economic importance, it is widely distributed in the USA, Canada, Europe, Siberia and Japan.

- Poplar borer (Saperda carcharias): it is a beetle whose larvae pierce galleries along the trunk and branches. It is a common species in Europe and part of Asia.

- Woolly poplar aphid (Phloeomyzus passerinii): insect of the Aphididae family that causes damage by sucking sap from tender tissues and shoots. Its damage is more serious in hybrids of Euro-American origin, mainly affecting commercially propagated clones.

- Poplar borer caterpillar (Sesia apiformis): borer lepidopteran whose caterpillar stage feeds on the tissues of species of the genus Populus. The caterpillar mainly affects the formation of trees, the galleries cause the sap ducts to break and weaken the affected feet.

References

1. Arthaud, J. & Taris, B. (1979). The diseases of poplars. Pest Service Bulletin, 5, 13-24.
2. Poplar of Castilla y León (2018) Pests and diseases. Castilla y León Forest Portal. Recovered in: populuscyl.es
3. De Lucas, AI, Sierra, R., Cristóbal, MD, López, U., San Martín, R., & Martínez, P. (2001). Characterization of Populus alba L., Populus tremula L and Populus x canescens (Ait.) Sm. species by morphological characters and molecular markers. In 1. Symposium of Chopo, Zamora (Spain), 9-11 May 2001. JCYL, CMA.
4. Gutiérrez Bustillo, AM (2018) Poplar, poplar. Populus L. Faculty of Pharmacy of the UCM DIATER Laboratorios.
5. Martín Bernal, E. & Ibarra Ibáñez, N. (2011) Plagas del Poplar. RedForesta: Social Network of Natural Environment Professionals. Recovered in: redforesta.com
6. Populus (2020). Wikipedia, The Free Encyclopedia. Recovered at: es.wikipedia.org
7. Populus sp. (2018) Argentine National Pest Surveillance and Monitoring System. Recovered at: sinavimo.gov.ar
8. Populus L. (2013) Iberian Trees. Recovered in: arbolesibericos.es