- Name also: Common Aspen, Eurasian Aspen, European Aspen, Quaking Aspen
- Family: Willow Family – Salicaceae
- Growing form and height: Tree. 15–30 m (50–100 ft.).
- Flower: Female and male flowers on separate trees. Inflorescence a pendent, unstalked catkin. Scale reddish-brown, palmately lobed, lobes long-hairy. Individual flower small, lacking perianth, borne within a cup-like structure in the axil of a catkin scale. Stamens 4 to 10, usu. 8. Pistil formed from 2 fused carpels, stigmas reddish-brown
- Leaves: Alternate, chiefly on short shoots. Stalk 3–5 cm (1.2–2 in.), laterally flattened. Blade approx. as long as stalk, orbicular, pinnately veined, ovate on young plants and suckers, with winding or blunt-toothed margins, hairless. Autumn colour from reddish-orange to bright yellow.
- Buds: Rather long, with several budscales, sharp, sticky, glabrous.
- Fruit: Two-valved, hairless capsule. Seed bar-like, with long flying hairs at the base.
- Habitat: Dry to damp coniferous or broadleaf woods, rich swamps, burnt-over areas, rock outcrops, forest margins, etc. Also planted for timber and as an ornamental.
- Flowering time: April–June. Flowers before coming into leaf.
Poplars (Populus) are a very old genus. Fossils have been discovered in earth layers formed in the Cretaceous. The boundaries between different poplar species are often unclear. The genus is very diverse in the Mediterranean region, East Asia, and North America. Poplars are popular park trees and ornamentals.
Aspen has wind-pollinated flowers that appear before leaves in spring. It is a monopodially growing tree with rigid branches. It frequently produces suckers. Its leaves flutter in the slightest breeze due to the laterally flattened leaf-stalks which are easily bent sideways. Aspen comes into leaf quite late, often as late as in June. Despite this, it is a fast-growing tree, and rarely exceeds 100 years of age. It reaches considerable girth only on rich soils in broadleaf or mixed woods. As a pioneer species that thrives in open places it is a weak competitor, and is soon forced to give way to conifers.
Aspen is an important factor in maintaining the biodiversity of forest ecosystems as it provides a home for many species of animals, fungi, and plants. Wood is whitish, soft, and decay-resistant which makes it a suitable raw material in construction and for various implements. Traditionally, aspen wood has been used for making matches, plywood, and sauna benches.
Several aspen forms exist, even in Finland, e.g. Populus tremula ‘erecta’ (pillar aspen), f. salliensis (carpet aspen), f. gigas (giant aspen). P. tremula x tremuloides is a hybrid between aspen and American aspen. It is cultivated for ornamental use and also for wood material.
Balsam Poplar & Laurel Poplar & Western Balsam Poplar
Populus balsamifera & Populus laurifolia & Populus trichocarpa
In Finland aspen is the only natural member in genus Populus, but there are several ornamental varieties. The differences between species are quite unnoticeable and besides that different forms in different part of the world exist. Poplars are very popular (only one letter’s difference between poplar and popular) especially for decorating yards and parks. The most common park poplars in Finland are balsam poplar (P. balsamifera), laurel poplar (P. laurifolia) and black cottonwood (Western balsam poplar, P. trichocarpa, also classified as P. balsamifera ssp. trichocarpa). In Finland balsam poplar can reach the height of 15 m. Its leaves are ovate. Laurel poplar can reach the height of 20 m.. Its leaves are narrowly ovate or narrowly elliptic. Undersides of both leaves are light, buds are quite large and sticky, Staminate (male) plants are more common than pistillate plants.