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 the most common names..
It is one of the tallest pines in the world, with a thick, corky bark, soft and small needles and hanging cones with an ovoid-conical shape. The seeds maintain their viability for a long time and it is a monoecious species.
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 large 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 the larvae of Barbara sp., which infest pineapples and feed on their seeds. Its propagation can be carried out from seeds and through cuttings, cuttings and layers.
Article index
Douglas fir is a pine with a very beautiful crown, with a height between 20 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.
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. Produce a lemon or mandarin odor when rubbed.
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.
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..
-Kingdom: Plantae
-Phylum: Tracheophyta
-Class: Pinopsida
-Order: Pinales
-Family: Pinaceae
-Gender: Pseudotsuga
-Species: Pseudotsuga menziesii
Douglas fir is also known as Pseudotsuga flahaulti Flous, and how Abies menziesii.
Varieties can be found Pseudotsuga menziesii var. glauca, and Pseudotsuga menziesii var. menziesii.
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 scarcer in Mexico..
In the Aztec country it is included as a species under special protection, so its use for commercial purposes is not allowed. In addition, in this nation the Douglas fir populations 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 species Religious abies and to the genres Quercus Y Pinus, as well as sometimes with Arbutus Y Juniperus.
Some of the problems that alter their natural populations are land use change, improper 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 introducing them into native populations to increase the population itself and genetic diversity..
With respect 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.
Douglas firs produce a wood of excellent quality, it has thin knots, its shape is cylindrical and it is 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.
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.
Once the plants are large enough to be transplanted (between 18 and 25 cm), it is recommended to harden them a month before transporting them to the field. This is done by suspending fertilization and keeping the seedlings in direct sunlight and applying irrigation very infrequently, more or less every other day..
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 yellowish-green embryo. After collecting them in half-filled bags, they should be kept in the shade, and later labeled and transported to nursery conditions..
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..
The ideal pH is between 6 and 7.6. The substrate must retain moisture and have a rich to poor organic matter content.
To promote seedling growth, a calcium nitrate fertilizer is used. The combination of phosphorus and nitrogen in the fertilizer also favors the seedlings.
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 significant 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.
While young and adult trees are attacked by the bark beetle Dendroctomus pseudotsugae.
The mushroom Rhabdoline pseudotsugae it causes great defoliation in the adults of this pine. Likewise, dwarf mistletoes can also parasitize several species of Pseudotsuga, and cause the loss of vigor and increase the susceptibility of these conifers to other parasites.
The lepidopteran Choristoneura (Tortricidae) produces larvae that attack the mature cones and manage to feed from their external part, as well as feed on the foliage of this pine.
Yet No Comments