From Pine Tree to Pine Tar (and a bit about baseball)

Scots pine (Pinus sylvestris) is a Eurasian native, distributed across Europe into Eastern Siberia. It is the national tree of Scotland, and the only native pine in northern Europe. Human activity has pushed native populations to extinction; while, at the same time, appreciation for this tree has led to widespread introduction in other parts of the world. Like other pines, humans and Scots pine have a long relationship going back millennia. Pines are incredibly useful trees, which explains both the overexploitation and mass planting of Scots pine.

Scots pine (Pinus sylvestris) via wikimedia commons

In Sweden and other Scandinavian countries, Scots pine not only has a long history of being used as a building material, but also for producing pine tar. As the name suggests, pine tar is a dark, sticky substance extracted from pine wood. Wood tar production dates back centuries and has been made from a number of tree species, including pines and other conifers as well as deciduous trees like birch and beech. Wood tar has myriad uses – as an ingredient in soaps, shampoos, and cosmetics; as medicine; as a food additive; as waterproofing for ships, roofs, and ropes; in hoof care products for horses. It’s no wonder that as demand for pine tar increased in Scandinavia, it became a cash crop for peasants, earning it the nickname “peasant tar.”

Pine tar soap – a decent soap if you can tolerate the intense smell. Regarding the smell of pine tar, Theodore Kaye writes, “The aroma produces reactions that are as strong as the scent; few people are ambivalent about its distinctive smell.”

A study published in the Journal of Archaeological Science examines small and large funnel-shaped pits in Sweden determined to be used for making pine tar. The smaller pits date back to between 240 – 540 AD, the Late Roman Iron Age. They would have been used by Swedes living in small scale settlements. The larger pits date back to 680 – 1160 AD and signify a shift towards large scale production during the Viking Age. As the centuries proceeded, Sweden became a major exporter of pine tar. Their product set the standard. Even today “Stockholm Tar” refers to pine tar of the highest quality.

As Europeans colonized North America, they were introduced to several new pine tree species from which to extract pine tar, including longleaf pine (Pinus palustris), a southeastern native with exceptionally long needles. Pine tar production was especially prolific in the southeastern states, thanks in part to the abundance of longleaf pine and others. North and South Carolina were dominating production by the 1800’s, which helps explain North Carolina’s nickname, The Tar Heel State.

Extracting pine tar from pine wood is fairly simple. The process is called destructive distillation. Pine wood is placed in a contained, oxygen-free environment and subjected to high heat. As the pine tar is released from the wood, the wood turns to charcoal. This is what was happening in the small and large funnel-shaped pits discussed earlier. Root pieces and stumps of Scots pine were placed into the pits. Brush wood was piled on top and then set on fire. As the brush burned, the pine wood below carbonized, and pine tar collected at the bottom of the pit. In larger pits, the pine tar was piped out and deposited into a barrel – a set up known as a pine tar dale.

pine tar dale illustration

Modern production of pine tar is done in kilns (or in laboratories). The concept is the same – wood is enclosed in the kiln, heat is applied, and pine tar drips from the bottom of the kiln. Heartwood, also known as fatwood, is the best part of the pine tree for making pine tar, particularly the heartwood of old stumps. Making pine tar is such a simple process that anyone can do it, and there are numerous tutorials available online.

My familiarity with pine tar comes from being a baseball fan. Pine tar is a useful, albeit controversial, substance in this sport. Batters have a variety of means to help them get a better grip on the bat in order to improve their hitting. Rubbing pine tar on the bat handle is one of them. However, according to Major League Baseball rules, anything applied to, adhered to, or wrapped around the bat to help with grip is not allowed past the bottom 18 inches of the bat. Pine tar is allowed on the bat handle, but if applied past that 18 inches mark, the bat becomes illegal.

pine tar stick for baseball bat handles

This rule goes mostly ignored; unless, of course, someone on the other team rats you out. Which is exactly what happened in 1983 to the Kansas City Royals in a game against the New York Yankees. Royals batter, George Brett, had just hit a home run, which put the Royals in the lead. It had been suspected for a while that Brett had been tarring his bat beyond the legal limit, and this home run was the last straw for Yankees manager, Billy Martin. He brought the suspected illegal bat to the attention of the umpires, and after measuring the bat’s pine tar stain they found it to be well beyond 18 inches. The home run was recalled, and the Yankees went on to win the game.

It doesn’t end there though. After a repeal, it was decided that the dismissal of the home run was the wrong call. If an illegal bat is in play, it should be removed. That’s all. The home run still stands. The Royals and Yankees were ordered to replay the game, starting at the point where Brett had hit his home run. This time the Royals won.

This saga is well known in baseball. There is even a book all about it, as well as a country song and t-shirts. But that’s only part of baseball’s pine tar controversy. While batters are allowed to use it on their bats, pitchers are not allowed to use it to better grip the ball while pitching (however, they can use rosin, which curiously enough, is also made from pine trees). Of course, that doesn’t stop them from trying to get away with it. Sometimes they get caught, like Michael Pineda infamously did in 2014. There are arguments for allowing its use – and perhaps in the future the rules will change – but for now pine tar use by pitchers remains prohibited.

Further Reading – Medicinal Uses for Pine Tar:

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Inside of a Seed: Gymnosperms

“Every tree has to stay where it put down roots as a seedling. However, it can reproduce, and in that brief moment when tree embryos are still packed into seeds, they are free. The moment they fall from the tree, the journey can begin.” — The Hidden Life of Trees by Peter Wohlleben

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Seed plants – also known as spermatophytes – make up the largest group of plants on earth. Seed plants consist of five divisions, and among them the angiosperm division (a.k.a. flowering plants) dominates in its number of species. The four remaining divisions are referred to collectively as gymnosperms. This incudes the cycads (Cycadophyta), Ginkgo biloba (the only living species in the division Ginkgophyta), gnetophytes (Gnetophyta), and the conifers (Coniferophyta). Conifers are by far the largest and most widespread gymnosperm division.

Angiosperms and gymnosperms have different evolutionary histories, resulting in their distinct genetic and morphological differences. That being said, an overly-simplistic way of differentiating the two groups is to say that, while both groups produce seeds, angiosperms produce flowers and fruits while gymnosperms produce pollen cones and seed cones. There are always exceptions (Ginkgo biloba, for example, doesn’t produce cones), but for the most part, this is the case.

Pollen cones (top) and seed cones (bottom) of mugo pine (Pinus mugo) via wikimedia commons

Sexual reproduction in gymnosperms follows a familiar pattern. Pollen, which contains the male sex cells, is produced in pollen cones, which are essentially miniature branches with modified leaves called scales that house the male reproductive organs. Mature pollen is shed and carried away by the wind. Lucky pollen grains make their way to the female cones, which are also modified branchlets, but are a bit more complex. Scales sit atop bracts, and on top of the scales are ovules – the female reproductive structures. During fertilization, the bracts open to collect pollen and then close as the seed develops.

When pollen lands on an ovule it forms pollen tubes that help direct the male sex cells to the egg cells inside. The process is similar to pollen tubes extending down the style of a flower. In flowering plants, additional pollen cells combine with cells in the ovule to produce endosperm, a storage tissue that feeds the growing embryo. This doesn’t happen in gymnosperms. Instead, haploid cells within the ovule develop into storage tissue and go on to serve the same role.

The ovule eventually matures into a seed, and the cone opens to release it. The seed sits atop the scale rather than enclosed within a fruit, as it would be in an angiosperm. For this reason gymnosperms are said to have naked seeds. The development of seeds can also be much slower in gymnosperms compared to angiosperms. In some species, seeds don’t reach maturity for as long as two years.

Seed cones and winged seeds of mugo pine (Pinus mugo) via wikimedia commons

Seeds in the genus Pinus are excellent representations of typical gymnosperm seeds. Their basic components are essentially identical to the seeds of angiosperms. The seed coat is also referred to as an integument. It was once the outer covering of the ovule and has developed into the seed covering. A micropyle is sometimes visible on the seed and is the location where the pollen cells entered the ovule. The storage tissue, as mentioned above, is composed of female haploid cells that matured into storage tissue in the ovule. Like angiosperms, the embryo is composed of the radicle (embryonic root), the hypocotyl (embryonic shoot), and cotyledons (embryonic leaves).

Angiosperms can be divided into monocotyledons and dicotyledons according to the number of cotyledons their embryos have (monocots have one, dicots have two). Gymnosperms are considered multi-cotyledonous because, depending on the species, they can have a few to many cotyledons.

Seedling of Swiss pine (Pinus cembra) showing multiple cotyledons via wikimedia commons

For the sake of this introduction to gymnosperm seeds, I have offered a simple overview of the production of seeds in the conifer division. Sexual reproduction and seed formation in the other three gymnosperm divisions is a similar story but varies according to species. Even within the conifers there are differences. For example, the “seed cones” of several gymnosperm species can actually be quite fruit-like, which serves to attract animals to aid in seed dispersal. Also, the pollen of gymnosperms is often thought of as being wind dispersed (and occasionally water dispersed in the case of Ginkgo biloba and some cycads); however, researchers are continuing to discover the pivotal role that insects play in the transfer of pollen for many cycad species, just as they do for so many species of angiosperms.

All of this to say that Botany 101 is simply a window into what is undoubtedly an incredibly diverse and endlessly fascinating group of organisms, and that, as with all branches of science, there is still so much to discover.