Finnish-Swedish botanist and student of Carl Linnaeus, Pehr Kalm (born Petter) is famous for the early botanical exploration of North America. Born in Angermanland, Sweden, his family fled there from Finland where his father was a Finnish Lutheran minister in the town of Närpes (Ostrobothnia) at the time of the Russian occupation (1710-1721). Although his father died soon after Pehr's birth, he and his mother returned to Finland after the war ended and they lived in some poverty in a village near Vaasa.

Educated with the help of various patrons Kalm managed, in 1735, to attend the only university in Finland, the Åbo Akademi in present day Turku. One such patron was a Swedish Baron who spent a good deal of time working in Åbo as a judge. S.C. Bielke entrusted Kalm with the management of his estate just outside of Uppsala in 1740, seeing that Kalm was enthusiastic and talented in the field of natural history, he paid for him to attend the University of Uppsala. Here Kalm met Linnaeus, professor of medicine at the university from 1741, who was so impressed by the young Kalm that he agreed to give him private tuition for free. Kalm also received special tuition from Anders Celsius, who taught the Finn astronomy and how to measure latitude. Between 1742 and 1745 he was able to travel extensively in Finland, Russia and Sweden with Bielke and widely explored the flora of the region. Bringing his findings back to Linnaeus, which were used in his Flora Suecia, Kalm soon became a favourite student of the professor.

In 1747, on his master's recommendation, Kalm was named docent of natural history and economics back at the Åbo Akademi. This was partly so that he might be funded in further expeditions, which the professors at Uppsala were planning for him. The same year it was decided that his expertise and perseverance would be best utilised on a trip to the New World and arrangements were made for him to travel to North America. The main purpose of the trip was to bring back plants of economic value which could be cultivated Scandinavia, and they were particularly keen to find a hardy species of mulberry which might be used to start a silk industry there. Kalm was also tasked with taking general cartographic and astronomic measurements.

Taking with him Bielke's own most trusted servant, Lars Jungström (with whom he maintained a fantastic working relationship throughout his journey) Kalm set sail for America via England. Spending several months awaiting passage out of London he met various academic figures, collected plants and befriended farmers for their knowledge. In 1748 they set sail for Philadelphia and soon after settling he met with Benjamin Franklin who in turn introduced him to many local academics, including the botanist John Bartram whose understanding of the local flora was unparalleled. Bartram's knowledge would provide Kalm with the basis on which to make his own observations, and he studied the plants in Bartram's private botanical garden. Collecting seeds and plants on many short excursions in the area, Kalm sent his haul back to England and towards the end of the year visited C. Colden in New York where he also botanised. Luckily the War of the Austrian Succession was just ending in Europe and so a brief spell of peace passed through the otherwise dangerous region between New England and Canada. This allowed Kalm to travel north and so search for plants growing at the same latitude as Sweden. Also, holding a passport from a neutral country, he received hospitality in both British and French occupied territories and found his way safely through no-mans-land to Montreal in the summer of 1749. After a gruelling journey up the St. Lawrence River he was welcomed as a dignitary and soon continued on to Quebec where he remained for a while to botanise. Returning to Philadelphia via Albany and Saratoga in November, he had gathered many plants of potential economic importance in Sweden such as walnut, early-ripening maize, pumpkin, cotton and watermelon. Kalm also took many barometric, meteorological and cartographic measurements along the way.

The following year he married the widow Anna Margaretha Sandin and obtained permission to travel to Niagara via Oswego the following spring. Journeying through Iroquois territory he became the first to accurately document the Niagara Falls and made further important collections. Returning late in 1750 Kalm remained in Philadelphia until early 1751 when he travelled back to Sweden with Margaretha and her daughter, as well as a pair of opossums, a tortoise and a guinea pig. After meeting with Linnaeus, Kalm and his family returned to Turku where he continued to work as a lecturer, teaching an extremely popular course on his findings from the expedition. Living in Slottsgatan he had a son and began to cultivate the seeds from his expedition in a garden he rented from the crown in Seipsalo. In 1752 Kalm published his travel journal which became very popular, particularly abroad, and was translated into German, French, Dutch and English. By 1778 he had also published 17 scientific papers in the Proceedings of the Royal Swedish Academy of Sciences. An advocate of silviculture and forest conservation, in later years Kalm's attention returned to the plants of Finland and he published a Flora fennica in 1765, containing the descriptions of 925 plants. Kalm and his wife both longed to return to Pennsylvania and he even considered moving back to work as a Lutheran priest, but unfortunately he died before this dream could be realised. Although he failed to successfully cultivate any plants which could feasibly be of economic value (even his mulberry trees died in the winter of 1770-1771), Kalm did influence the next generation of botanical explorers in Finland, his collections were cited heavily in Linnaeus' Species plantarum and Kalm's extensive and clear descriptions of life in England, Pennsylvania, New York, Montreal and Quebec remain valuable today as they were when they were published.

Sources:
R.E. Fries, 1950, A Short History of Botany in Sweden
P.I. Robbins, 2007, The Travels of Peter Kalm
F.A. Stafleu, 1971, Linnaeus and the Linnaeans.