The Douglas fir: a giant Christmas tree

With its tall and elegant conical crown, the Douglas fir (Pseudotsuga menziesii) is one of the most sought after species as a Christmas tree. Also known as the Oregon pine or pseudotsuga, it is native to the west coast of North America, where it is one of the most sought after species for decoration during Christmas festivities.

All trees dig their roots into the earth and extend their branches towards the sky in order to guarantee their place in the sun. In this unbridled race to the light, the towering Douglas fir is undoubtedly one of the winners. In its native region, it can reach 100 metres in height. It is one of the tallest species in the world, and can live for up to 1,000 years.

In Portugal, however, it is normally half that height, i.e. approximately as tall as a 17-storey building. The species is said to have arrived in Portugal in 1840, and was valued for both its ornamental beauty and its wood. Although it is not a common tree in Portugal, it can be found in parks, gardens and small plantations in various mountain ranges in the north and centre of the country.

The Douglas fir can be distinguished above all by its evergreen foliage, its straight trunk and its conical, broad crown when it is in its juvenile stage. These attributes have made it one of the most popular species for Christmas trees, especially in the United States. In Portugal, however, it is not a common choice, as it is quite scarcely and dispersedly distributed. Christmas tradition amongst the Portuguese has mainly favoured the maritime pine (Pinus pinaster), a species from the same family as the Douglas fir – Pinaceae, which is much more widespread in Portugal.

As with the other members of the Pinaceae family, the Douglas fir does not have flowers, but male and female reproductive structures (so-called strobiles or cones, from which the term conifer, which covers many species of gymnosperms or conifers, is derived). We call them pine cones and they appear between March and May, and they store pollen and seeds. Males are about 2 centimetres long and yellow-orange in colour and females reach up to 10 centimetres in length, and are also more visible because of their colours: yellowish-green when young and reddish-brown when mature. Pine cones can easily be distinguished by their unmistakable protective scales, which are protruding, long and trifurcated at the tip.

In young specimens of Douglas fir, the protective bark (rhytidome) is greyish in colour and covered with resinous vesicles; while in older specimens, it becomes woody and cracked and has a reddish-brown tinge. The branches also change colour with age: initially they are yellowish green, then yellowish brown, and finally grey and covered in short, fine, soft hairs.

The green, needle-shaped leaves, which measure up to 3.5 centimetres in length, are arranged in a spiral and have two white stripes on the underside. When squeezed, they release an aromatic odour.

Did you know that the Douglas fir…

• Has only one specimen classified as a Tree of Public Interest in Mainland Portugal? It is located near the Sanctuary of Nossa Senhora do Carmo da Penha, in Guimarães. It is about 70 years old, measures 4.8 metres in circumference at chest height and is 35 metres tall. It is not, however, the largest example recorded in Portugal: that is in the Buçaco National Forest and is a green giant of around 150 years old, measuring 4.6 metres in circumference and 53 metres tall, equivalent to the height of the Monument of the Discoveries in Belém, Lisbon.
• Was first planted in Portugal in the Parque da Pena, in Sintra, at the request of King Fernando II, in around 1840. It was then introduced into the Buçaco forest (1871), the mountains of Estrela and Gerês (1904/05), and the Padrela mountains (1970). In addition, this species—particularly the variety menziesii—can be found in plantations on other mountain ranges, such as Açor, Bornes, Cabreira, Caramulo, Ladário, Leomil, Lousã, Malcata, and Nogueira. The preference for this variety—often referred to as pseudotsuga-da-faixa-litoral—mainly lies in its rapid growth and the monetary value of its high-quality wood.
• Owes its scientific name Pseudotsuga menziesii to the Portuguese botanist João do Amaral Franco who, in 1950, suggested changing its former name Abies menziesii, attributed to Frenchman Charles-François Mirbel, in 1825. The name of the genus (Pseudotsuga) is intended to show that this is not a true tsuga, another species native to the American continent. The species name menziesii is a tribute to the Scottish naturalist Archibald Menzies (1754-1842), who discovered and described the species for the first time in 1795. The common name, Douglas fir, honours the Scottish botanist David Douglas (1799-1834).