Tree a Week: Poplar

Black poplar, known for its narrow and column like stature.

Interesting facts

  • There are around 25 to 35 species of poplar (not including hybrids), from the genus Populus which is in the willow family Salicaceae.
  • Poplar are native to most of the Northern hemisphere, commonly named species include cottonwood, aspen and balsam.
  • They are rapid growing, growing 7m in 5 years however their lifespan is rather short lived. Their average live span is 15 to 50 years, growing up to heights of 50 metres, although some poplar have been known to live up to 200 years.
  • Poplars have very invasive root systems stretching 40m from the tree trunk, planting poplars near to buildings can result in damaged foundations and cracked walls.
Global distribution map of the black poplar also known as the lombardy.

Uses

  • Poplar wood is relatively soft and grows quickly making it cheaper to produce than other woods. It’s inexpensive timber is predominately used to make cheap plywood, matches, pallets, cardboard boxes, and paper.
  • Poplar wood is commonly used in snowboards due to its lightness in weight and flexibility.
  • There is also an increasing demand for hybrid poplar chips, which makes great fuel for pellet stoves and mulch.
Snowboard core made from poplar timber.

Threats, ecological and fungal relationships

Several species of Populus in the United Kingdom and other parts of Europe have experienced heavy dieback because of the hornet moth, Sesia apiformis, boring itself into the tree’s trunk during its larval stage.

The black poplar (populus nigra) which is native to the UK and Europe grows in isolation and is the most endangered native timber tree in the UK.

Populus are prone to a variety of fungal diseases including cankers, leaf rusts and poplar scab. Pleurotus populinus, the aspen oyster mushroom is found exclusively on dead wood of Populus trees in North America.

Aspen oyster mushrooms colonising a dead poplar.

Poplars thrive in very wet soil, they help prevent erosion and are planted to clean contaminated groundwater at treatment sites and along streams and rivers. They have vigorous root systems, almost all poplars take root readily from cuttings or where broken branches lie on the ground. Poplars are also vital food sources for a number of moths and butterfly larvae, Lepidoptera species. 

Identification

Bark: The bark is dark brown but often appears black, it can vary with a mixture of diamond lentils or thick, numerous fissures and furrows. The twigs are lumpy and brown in colour.

Leaves: Shiny, green and heart-shaped, with long tips and a mild scent of balsam. Young leaves are covered in fine, tiny hairs, which they shed by autumn.

Flowers: Black poplar is dioecious, this means male and female flowers are found on separate trees. Flowers are catkins (male catkins are red and female catkins are yellow-green), and are pollinated by the wind. 

Fruits: Once fertilised, female catkins develop into fluffy cotton-like seeds, which fall in late summer. 

Female catkin that has been fertilised.

Further Reading

One of the great uses of poplar is as mushroom logs. Popular wood is soft and the mycelium colonises the logs quickly, producing large amounts of mushrooms during fruiting season. The book that really got me interested in growing mushrooms and in particular the suitability of popular for this purpose was this book, written by none other than Paul Stamets.

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