PSEUDOTSUGA MENZIESII: CHARACTERISTICS, HABITAT, USES, DISEASES - BIOLOGY - 2025

Pseudotsuga menziesii or Douglas fir, is a conifer belonging to the Pinaceae family. This pine is known as Douglas fir, Oregon pine, red royal pine, cahuite, spruce, and red guayamé, as more common names.

It is one of the tallest pines in the world, with a thick and corky bark, soft and small needles and hanging cones in an ovoid-conical shape. The seeds maintain their viability for a long time and it is a monoecious species.

The female strobili hang from the branches and have protruding bracts. Source: wikimedia commons.

The name of this pine is in honor of the botanical collector and explorer David Douglas (1799-1834), who introduced this species to Europe in 1827. It is a species with a great presence in the United States, Canada and Mexico, where it is considered protected.. It is of great commercial importance due to its excellent quality hardwood and a beautiful reddish-brown color.

Douglas fir is also very commercial, especially at Christmas time, and is highly exported. For this reason, indiscriminate felling and harvesting of this species of pine occurs.

Seed production is affected by various insects, especially Barbara sp. Larvae, which infest pineapples and feed on their seeds. Its propagation can be carried out from seeds and through cuttings, stakes and layers.

characteristics

Appearance

Douglas fir is a pine with a very beautiful crown, with a height between 20 m and 40 meters, although some can reach 100 meters. The diameter can be up to 3 meters and it is an evergreen tree.

Its bark is thick, corky and cracked. The crown is irregular but very striking for its hanging twigs.

Leaves

The leaves always remain on this species of pine, even after cutting. They are dark green in color and form a kind of brush along the branches. They produce a lemon or tangerine smell when rubbed.

The needles of this pine are soft and form a kind of brush along the branches. Source: Crusier

The needles are soft and flexible. They are 15 to 30 mm long and have a rounded apex. When removed, they leave an oval-shaped scar on the twigs.

Reproductive structures

The male inflorescences are yellowish, while the female ones have a greenish or reddish color. Flowering occurs from April to May, and pollen is spread from May to April.

Like any pine, it produces cones, which in this case mature from August to September and every 4 or 6 years. The pineapples are ovoid-conical, pendant and measure up to 10 cm in length.

It is characteristic that trifid bracts protrude from the pineapples between their scales. The seed can be dispersed through the wind. The male strobili are axillary and are found in large numbers on the lower part of the branches, while the female strobili are pendulous.

Cross pollination must be carried out between individuals of populations with similar environments to ensure their adaptation.

Douglas fir is a very ornamental species. Source: pixabay.com

Taxonomy

-Kingdom: Plantae

-Filo: Tracheophyta

-Class: Pinopsida

-Order: Pinales

-Family: Pinaceae

-Gender: Pseudotsuga

-Species: Pseudotsuga menziesii

Douglas fir is also known as Pseudotsuga flahaulti Flous, and as Abies menziesii.

The varieties Pseudotsuga menziesii var. glauca, and Pseudotsuga menziesii var. menziesii.

Douglas fir is one of the tallest pines in the world. Source: Cathy from USA

Habitat and distribution

It is a species native to North America, where it is very important and abundant in the western United States and Canada, while it is more rare in Mexico.

In the Aztec country it is included as a species under special protection, so its use for commercial purposes is not allowed. Furthermore, Douglas fir populations in this nation are isolated and dominated by other species.

This tree grows naturally in the states of Chihuahua, Sonora and Zacateca, in the Sierra Madre Occidental in Nuevo León (Mexico). It is found forming part of the vegetation such as the fir forest, the pine-oak forest and the pine forest. In addition, it is associated with the Abies religious species and the Quercus and Pinus genera, as well as sometimes with Arbutus and Juniperus.

Some of the problems that alter their natural populations are land use change, illegal logging, overgrazing, seed collection, and pests that affect this species.

To reduce these environmental problems, it is considered necessary the assisted migration of specimens belonging to foreign populations and to introduce them into native populations to increase the population itself and genetic diversity.

With regard to the edaphoclimatic requirements, it grows from 1500 to 3600 meters above sea level. It is found in soils such as Regosol, Leptosol, Cambisol, and Feozem, according to the FAO classification, with a loamy-sandy, clayey and clay-silty texture. Some stony ground is required.

The precipitation that occurs in these places is around 1200 mm per year, with a minimum of 600 mm and a maximum of 1800 mm. It is a species with a medium tolerance to drought.

Applications

Douglas firs produce excellent quality wood, have fine knots, are cylindrical in shape and are quite hard. It is used for plywood, boats, pylons, window frames, packing boxes, piers, tanks, both exterior and interior finishes, for extracting cellulose and for handicrafts.

Likewise, they are in high demand for the Christmas season, since they have a beautiful shape in their crown and keep their leaves after the tree is cut.

Its commercial use has really been indiscriminate. In 2007 alone, almost 1,200,000 trees were exported to Mexico from the United States and Canada. For this reason, whole trees and their seeds are collected excessively.

Needles of Pseudotsuga menziesii. Source: wikimedia commons.

Culture

Spread

Douglas fir can multiply sexually or asexually. In the case of sexual propagation, the seeds must come from trees free of pests and diseases, with a vigorous bearing and that have had a good production of cones.

Seed-producing trees must have a planting distance of more or less 100 m between them; this to avoid collecting sister trees. However, in some countries it is customary to use a planting distance that is at least twice the average height of these trees.

The seed does not require pre-germination treatments, but it must be hydrated for at least 48 hours before sowing. The germination percentage that the seed normally has is around 60%.

Asexual propagation of this species of pine can be done by layering, staking, and cuttings. These structures must be obtained from branches and stems of young trees. Normally, the application of phytohormones increases the percentage of rooting.

It is recommended to leave only one plant or stake for each pot, after having eliminated the less vigorous ones.

Transplant

Once the plants are large enough to be transplanted (between 18 and 25 cm), it is recommended to harden them one month before transporting them to the field. This is done by suspending fertilization and keeping the seedlings in direct sun and applying irrigation very infrequently, more or less every other day.

Collect

The cones must be collected directly from the tree, between the months of August and September. It is advisable to climb the tree and cut the cones manually, taking care not to damage the branches and meristems so as not to affect the production of cones for the following season.

These cones should be collected when they have a golden brown color, a brown wing and the endosperm of the seeds shows a green-yellowish embryo. After collecting them in half-filled bags, they should be kept in the shade, and later labeled and transported to nursery conditions.

Weeding

Weeding must be carried out continuously in nursery conditions, especially in the corridors and inside the pots that contain the seedlings, and in this way, competition for light, water and nutrients is avoided, in addition to reducing the risk of diseases and pests..

Substratum

The ideal pH is between 6 and 7.6. The substrate must retain moisture and have a rich to poor organic matter content.

Fertilization

To promote the growth of seedlings, a calcium nitrate fertilizer is used. The combination of phosphorus and nitrogen in the fertilizer also favors the seedlings.

Douglas fir is a very commercial species, especially in the Christmas season. Source: wikimedia commons.

Diseases

According to the structure of this pine, diseases and pests vary. For example, seeds and cones are susceptible to attack by insects such as Pityophthonis orarius, Critonia oregonensis, Comptomyia pseudotsugae, Critonia washigtorensis, among others.

Another insect that causes important losses are the larvae of Barbara sp., Which infest the pineapple and consume the seeds. These larvae have a negative impact on the regeneration of this species of conifer.

Meanwhile, young and adult trees are attacked by the bark beetle Dendroctomus pseudotsugae.

The fungus Rhabdoline pseudotsugae causes large defoliation in the adults of this pine. Likewise, dwarf mistletoes can also parasitize various species of Pseudotsuga, causing loss of vigor and increasing the susceptibility of these conifers to other parasites.

The Choristoneura lepidopteran (Tortricidae) produces larvae that attack mature cones and manage to feed from the outside, as well as feed on the foliage of this pine.

References

1. Ventura, A., López, J., Vargas, JJ, Guerra de la Cruz, V. 2010. Characterization of Pseudotsuga menziesii (MIRB.) Franco in central Mexico. Implications for its conservation. Rev. Fitotec. Mex. 33 (2): 107-116.
2. Catalog of Life: 2019 Annual Checklist. Pseudotsuga menziesii (Mirb.) Franco. Taken from: catalogueoflife.org
3. SIRE-Technological packages. 2019. Pseudotsuga menziesii. Taken from: conafor.gob.mx:8080
4. Ornamental trees. 2019. Pseudotsuga menziesii (Mirb.) Franco. Taken from: arbolesornamentales.es
5. Infojardín. 2019. Oregon Pine, Douglas Fir. Taken from: chips.infojardin.com