Fall Colors

While researching our trip to Boston, Massachusetts and Vermont last year, I came upon a clear and concise description of how leaves turn colors in the fall, posted on the Stowe Fall Foliage web site. It is simplified, without bringing in the intricate interplay of plant hormones and environmental conditions that you might read about in a botany book. Here is the simplified version, with full credit going to the Stowe Fall Foliage site.

Yellow, orange, and red leaves in mid-Vermont

On the longest day of the year, June 21, chemical changes begin in the tree that later produces the fall foliage colors. As the days grow shorter and temperatures drop, green chlorophyll moves from the leaf to the branch, revealing the yellow and orange pigment that was always in the leaf. Warm fall days produce sugar, which is trapped in the leaf when the temperature drops at night. The leaves turn hues of red as the sugar accumulates. The article then describes the colors you can expect to be produced by leaf type in Vermont:

• Red (and some yellow) – sugar maple, red maple, red oak, sweet gum, black gum and sourwood
• Gold and yellow – birch, elm, poplar, redbud and hickory
• Maroon – sumac

Gold and yellow leaves near Hildene House in southern Vermont

If you want a little more information about the interplay between plant hormones and environmental conditions needed to produce fall colors, I recommend Botany for Gardeners by Brian Capon. He describes the processes and conditions at work to produce fall leaf colors, prepare for leaf drop, drop the leaves (the leaf scar prevents sap from bleeding out), and go dormant.
 

Transporting Plants

A challenge for botanists and plant collectors was getting plant specimens to their destinations. Most of the collectors we have studied so far, transported their collections by ship. Besides the ultimate threat of running aground or sinking, their were other challenges – ships were small and crowded; resources like fresh water were limited; and salt air and water could easily claim the specimens. How did these botanists transport their collections? Penelope Hobhouse sheds some light on the question in her book, The Story of Gardening.

• Seeds – this may have been the easiest way to transport plants, in their seed form. Seeds are small and compact, and contain everything needed to germinate the plant. They can be dried, and can last a long time. According to Hobhouse, seeds were sometimes coated in beeswax and wrapped in waxed cotton and paper, or bottled and packed in boxes of salt to keep them fresh and protected.

• Live plants – sometimes living plants were transported. Many containers were devised for the purpose, including woven baskets, and wooden crates. The plants required constant care on the journey to ensure their survival, and many plants died. In 1833, Dr. Nathaniel Bagshaw Ward developed miniature greenhouses for transporting live plants. These “Wardian cases” provided a sealed ecosystem for the plants during their voyage, and reduced loss.

Banksia serrata specimen collected from Botany Bay, Australia by Joseph Banks and Daniel Solander
(the plastic bag is obviously modern)

• Dried specimens – botanists collected plant parts, including seeds, leaves, and stems. Each specimen was dried thoroughly, and then pressed between sheets of paper for preservation. Stacks of pressed specimens were clamped together between wood planks, to protect them from damp conditions on their way to the herbariums of Europe.

In these ways, plants traveled the world to new destinations for study, commerce, and enjoyment.

Sir Joseph Banks

Sir Joseph Banks (1743 – 1820) was a key player in the movement of plants in the 1700s. He was born in London, England to wealthy parents, and developed an interest in botany when he was 14. He collected local plant specimens, and learned all he could from the local women who collected herbs. He was sent to Oxford for formal schooling. Bank’s father died in 1761 when he was 18. At 21 Banks inherited great wealth, but determined to put it to good use in pursuit of his interests.

Joseph Banks (photograph of a painting by Joshua Reynolds)

While at Oxford, Banks met Linnaeus apostle Daniel Carl Solander, who had been sent to London in 1760 to catalog the garden of Peter Collinson, and then accepted an assistant’s post at the British Museum. Banks and Solander became friends and colleagues. Instead of taking “The Grand Tour of Europe” that was popular with young men of his class, Banks went on a fishery protection patrol in Newfoundland and Labrador, and collected live and dried plant specimens.

Solander introduced Banks to the scientific community in London. At the age of 23, Banks was elected a Fellow of the Royal Society. Banks promoted the idea of accompanying Captain James Cook on his first voyage of geographical and scientific exploration, and joined the expedition as chief naturalist at the age of 25. He funded additional artists, botanists, and scientists to join, including Solander. Between 1768 and 1771 the HMS Endeavor visited Africa, South America, New Zealand, Australia, and Tahiti. They made many scientific discoveries, and collected many plant specimens.

Banksia ericifolia native to Australia

Upon return to London in 1771, Banks became President of the Royal Society, and worked with King George III to expand Kew Gardens. Through his influence and means, Banks sent botanists and collectors all over the world; commissioned botanical artists; corresponded with scientists and botanists; and added to the collections at Kew Gardens and the British Museum. His plant and geographical knowledge enabled him to consult on many projects, including the ideas to transport breadfruit to the West Indies on the HMS Bounty, and establish a penal colony at Botany Bay in Australia. Banks knew many influential people of his day, including Ben Franklin in America, and Carl Linnaeus in Sweden. He is honored with a genus of plants named after him, Banksia.

Garden History – Plants on the Move

This year I’m taking a side trip from the usual course of garden history study. Earlier this year we focused on gardens of the Americas to learn more about how gardens were developing independently in the New World (see Garden History – The Americas). In parallel, we have been learning more about several of the Linnaeus apostles, who were sent out in the 1700s to spread the word about the new taxonomy promoted by Carl Linnaeus, and to collect plant specimens from all over the world (see The Linnaeus Apostles). Now we are focusing on gardening history through the lens of “plants on the move”, using a chapter from Penelope Hobhouse’s book, The Story of Gardening.

Ships transported seeds, dried plant specimens, and live seedlings all over the world.

According to Hobhouse, in Chapter 6, “Plants on the Move: Botanists, Collectors, and Artists”, in the wake of the Renaissance there was a shift in the relationship between people and plants. New professions and avocations were born, and everyone became enamored with plants. Explorers collected them, botanists studied them, artists depicted them, nurserymen propagated and sold them, entrepreneurs looked for ways to profit from them, physicians employed their healing properties, and enthusiasts grew them. With advances in printing, books and prints became more readily available so information spread quickly. Hobhouse cites three major plant sources in this era:

• Old World and Levant – collectors became enamored with bulbs and plants from the Mediterranean and the Levant (an old term for Turkey).  European plant collectors in the 1600s became enthralled with tulip bulbs, which become a commodity for a short time (“Tulip Mania”). The bubble burst, but the interest in bulbs and plants remained. 
• The Americas – the trees and shrubs discovered in North America were also in high demand. The American botanist John Bertram of Philadelphia collaborated with European distributors to exchange plants and seeds. Carl Linnaeus praised Bertram as a botanist, and our Linnaeus apostle, Pehr Kalm, worked with Bertram – see Pehr Kalm in North America). According to Hobhouse, a more naturalistic gardening movement was emerging in the early 1700s, and the plants from America were ideal for this style.
• Exotics – collectors were sent out by botanical gardens and private enthusiast to collect plants from all over the world, including Asia, Australia, Africa, South America, and the tropics. These exotics were embraced and grown in gardens and hot houses far from their native climates. 

Hobhouse writes from a Western perspective, especially the English point of view, but Britain was a key player in the botanical exchange. It is good to keep in mind that plant exchanges have taken place all through history. Consider the Silk Road linking East and West; cultural exchanges between countries, such as Japan and China, and France and Russia; and migrations of people groups. These were all opportunities for plant movement, but the post-Renaissance era of exploration, colonization, and quest for economic gain coupled with advances in technology, accelerated the movement of plants across the globe like never before in history.