Among all the trees belonging to the coniferous genera, the genus Pinus is perhaps the hugest and most significant. Precisely speaking, this genus encompasses as many as 95 species and several ranges and crossbreeds. Trees belonging to the genus Pinus are extensively dispersed, especially in the Northern Hemisphere where they are found growing naturally from the sea level to the Arctic or Antarctic limit of tree growth (timberline). Pines may be found almost everywhere from Scandinavia to North Africa, from Alaska to Nicaragua and Siberia to Sumatra. While a number of pine species like the Scotch pine are extensively dispersed ranging from Scotland in Great Britain to Siberia, there are several species that are found growing in very restricted locations. For instance, the species called Canary Island pine is only found growing in the wild in the Canary Islands, while only a small number of trees belonging to the Torrey pine family are only found growing in two localities in California.
Among the 95 different species of pine, as many as 42 species are indigenous to America. However, reproduction of these Pinus species has enabled them to grow in different new locations now. All species of pines are perennial trees that grow to different heights. Usually the pine trees are very tall, but some may also be found as shrubs. In fact, a number of species of pines like the ponderosa pine, sugar pine and the western and eastern white pine often grow to a height of over 210 feet. In contrast, the Japanese stone pine and the Mexican pinyon hardly grow beyond the height of 33 feet.
Not much was known about the remedial properties of the genus Pinus till around 1992 when an extract derived from the external covering of the coniferous trees made attention grabbing news not only in America, but around the globe. This extract had practically transformed the entire antioxidant movement in the health food industry worldwide. The extract from the pine trees is known as pycnogenol and is mainly derived from the bark of the pine trees that covers the pines growing along the sea cost in Quebec province of Canada as well as the coast of the Atlantic Ocean in the southern regions of France.
As mentioned earlier, majority of the pine species are indigenous to the Northern Hemisphere and grow naturally in various regions. In the Eurasian region, pines grow in vast tracts of lands ranging from the Canary Islands, Iberian Peninsula and Scotland towards east of the Russian Far East. They are also found growing naturally in the Philippines, the northern regions of Norway, Sweden and Finland, where the variety is called Scotch pine, to the eastern regions of Siberia, where the species is called Siberian dwarf pine. The pines are also found in southern Africa to its northernmost region, Southeast Asia and the Himalayas. Only one species of pine called the Sumatran pine is found in Southeast Asia at the place where the Equator passes over Sumatra. A number of pine species are found in North America ranging from Canada to the southern region of Nicaragua. While the variety of pine found in Canada is called Jack Pine, in Nicaragua the variety is called the Caribbean pine.
Although most of the pine species are native to the Northern Hemisphere, over the years several species of pines have been introduced and naturalized in the sub-tropical as well as temperate climatic zone in the Southern Hemisphere, including places like Australia, New Zealand, South Africa, Brazil, Argentina and Chile. In most of these places, different varieties of pines are grown extensively for timber, but some of the species are gradually turning out to be intrusive.
Pines are actually evergreen and/ or sticky trees yielding resins that usually grow up to a height of 80 meters. However, a small number of pine trees are shrubby growing up to three or more meters in height. Nevertheless, the standard height of most of the pine trees range between 15 and 45 meters. The smallest pine trees include the Siberian dwarf pine and Potosi Pinyon, while sugar pine is the tallest pine trees. Pine trees usually live for long periods, usually attaining the ages between 100 and 1,000 years and some survive for even longer periods. It is surprising to note that the pine species that survived for the longest period is the Great Basin Bristlecone Pine (botanic name Pinus longaeva). A tree of this species lived for approximately 4,800 years becoming one of the longest surviving organisms worldwide.
Usually the bark of majority of the species of pine is chunky and crusty. However, barks of some pine trees are lean and flaking. The branches of the pine trees emerge from the ‘pseudo whorls’. In reality, the branches are extremely tight coils, but they resemble a ring of branches emerging from a common point. Several species of pines are uninodal, denoting that they produce merely one whorl of branches every year from the buds at the gradient of that year’s new sprout. However, majority of the pine species are multimodal that produces two or more whorls of branches every year. The twisted branches, needles as well as the cone scales of the pine trees are displayed in the ratio of Fibonacci sequence (an endless succession of numbers wherein each number barring the first two is the sum of the preceding two). Occasionally, the new sprouts appearing in spring are known as ‘candles’. In the initial stage, these sprouts are enveloped by whitish or brown bud scales and point skyward. Subsequently, the ‘candles’ become greenish and broaden away from the base. In fact, these ‘candles’ enable the foresters to assess the fertility of the soil as well as robustness of the pine trees.
The pine trees have four different varieties of leaves and they are as follows:
- Seed Leaves (Cotyledons)
- The seed leaves or the rudimentary leaves of the embryo of pine seed plants on seedlings are produced in a whorl of four to 24.
- Juvenile Leaves
- Subsequent to the seed leaves, the seedlings and young plants of the pine species develop juvenile leaves. These juvenile leaves are approximately 2 cm to 6 cm in length, are solitary and have a green or usually bluish green hue. They are positioned in a coiled manner on the new sprouts. The juvenile leaves usually appear between six months and five years of a pine tree’s existence, but usually not after five years.
- Scale Leaves
- The scale leaves of the pine trees are akin to the flakes on the buds – small and brown in color. These leaves are not photosynthetic and cannot utilize sunlight to produce food for the plants. Similar to the juvenile leaves, the scale leaves of pine trees are also positions in a coiled manner.
- The adult leaves of the pine trees are known as needles. These needle-like leaves are green in color and photosynthetic. The needles are packed together in groups and each close cluster of the needles (fascicle) is generated from a tiny bud on a dwarf sprout in the axis of a scale leaf. The scales of the buds continue on the fascicle and function as a basic covering. The needles of a pine tree survive between 18 months to 40 years conditional on the species. In case a sprout is ravaged, for instance, consumed by an animal, the tight clusters immediately beneath the damaged area will produce a new bud that is capable of replacing the leaves lost due to the animal attack.
Most species of pines are basically monoecious, denoting that each tree bears both male and female cones. However, there are a number of pine species that are dioecious too. In such species cones of one sex are predominant, but it does not mean that they bear cones of only one sex. Usually, the male cones are relatively smaller in size varying from 1 cm to 5 cm in length and remain only for a brief duration – generally they appear in spring and remain till autumn in a few species of pine. The pines drop off the trees soon after they shed their pollens. On the other hand, it takes anything between 18 months to three years for the female cones of pine trees to mature after they have been pollinated. In fact, the actual fertilization period starts about a year after the pollination. When they are fully mature, the female cones’ size varies between 3 cm to 60 cm in length.
Each female cone of the pine possesses several scales that are positioned in a coiled manner and each fertile scale of the cone encloses two seeds. It may be noted that the scales at the bottom and apex of the cones are not only relatively smaller in size, but also infertile, bearing no seed. The seeds of the pine are usually small is size and have wings. They are anemophilous by nature, denoting that they are dispersed by winds. However, there are a number of comparatively larger seeds with only one vestigial wing and are pollinated or dispersed by birds. Such seeds are found in a pine species called Whitebark pine and its seeds are liberated only when a bird opens the cone with its beaks. In other varieties of pine, such as the fire climax pines, for instance Pond pine and Monterey pine, the seeds are stocked up in blocked or ‘serptinous’ cones for several years till any forest fire destroys the parent tree. In addition to the birds opening the cones and releasing the seeds, they are also opened by heat. In such circumstances, the stored seeds drop off the fire ravaged ground and results in the new growth of pine trees in the area.
All pines thrive well in acidic soils, while some species are also able to grow on calcareous soils. Most of the pine species need well drained soil and hence, they have a preference for sandy soils. However, a number of species, such as the Lodgepole pine, can also endure soils that have poor drainage and are usually wet all the year round. Interestingly, a number of pine species, such as the Canary Island pine, are also able to germinate after forest fires. In fact, there are a number of pine species like the Bishop pine that require fire to renew growth and their number decline gradually when the fire is suppressed. On the other hand, numerous species of pines have the aptitude to withstand extreme conditions caused by change in latitudes and height of the land they are grown on. Some examples of such pine species include bristlecone pines, Mountain pine, Siberian dwarf pine and Whitebark pine. In fact, the pinyon pines as well as some other species, prominent among them are the Gray pine and Turkish pine, are especially acclimatized to grow even in hot, partially desert climates.
While the birds and squirrels generally consume the seeds of the pines, a number of birds, especially the Clark’s Nutcracker, Spotted Nutcracker and Pinyon Jay, play a vital role in dispersing the seeds to new regions and propagate the trees. A number of Lepidoptera (butterflies and moth) species also consume pine needles frequently. In addition, goats and the Symphytan species like Pine sawfly also eat pine needles.
All over the world, all varieties of pine trees are highly valued commercially for its timber and use as wood pulp. In fact, the softwood pine trees grow rapidly and very densely in the temperate and tropical climatic regions. In addition, the acidic needles of the pine trees slow down the germination and growth of any other rival hardwoods. Pine trees are grown commercially in plantations for their timber that is more compact, resinous and, hence, all the more enduring compared to spruce or Picea. Usually, the timber from pine trees is used for manufacturing sophisticated carpentry products like furniture, paneling, window frames, roofing and flooring, while the resin obtained from a number of pine species is a significant resource for turpentine.
In addition, several species of pines are used as ornamental plants to decorate parks and relatively bigger gardens, while an assortment of dwarf species are grown to accommodate in relatively smaller areas. Moreover, different varieties of pine trees are also cultivated as well as harvested as Christmas trees. On the other hand, the cones of the pine trees are not only the largest and most enduring among all conifer trees which are widely used to create craft items. The branches of pine trees are particularly valued, especially during the winters for their likeable aroma and greenery. They are usually cut during this time of the year for
decorative purpose. Some species of the pine are invaded by a phylum of parasitic worms (nematodes) that result in pine wilt disease (withering or drying out of the leaves and other parts), eventually causing their quick death. It may be mentioned here that the needles of the pine trees are used by different types of Lepidoptera (caterpillars and butterflies) as their favourite food.
Since the pine timber does not possess any insect or decomposing defiant properties after they are turned into logs, it is advisable that when they are being used for construction purpose, they should usually be used only in the interiors, barring indoor drywall framing. If the pine wood is left unattended outside, they are unlikely to last for over 12 or 18 months conditional on the sort of climatic conditions it is bared to. In fact, the pine wood is known by several names, including SPF (spruce, pine, fir), North American timber and whitewood.
As discussed earlier, a number of pine species have relatively larger seeds that are known as pine nuts. These pine nuts are collected as well as sold commercially for cooking as well as baking. The inner bark of pine trees known as cambium is pliable and soggy and always remains tightly attached to the woody exterior bark. The inner bark is also edible and contains rich amounts of vitamins A and C. Some people eat the inner bark raw as a snack after slicing it into smaller pieces, while there are others who dry the inner bark, grind it and use the powder to prepare foods like pine bread and also to coagulate soups and stews. A tea prepared by steeping juvenile, green pine needles in boiling water is called ‘tallstrunt’ in Sweden. This herbal tea is rich in vitamins A and C contents.