Was Kepler a bad mathematician? He apparently made lots of computational errors. What aids he used in his ciphering I don’t know. Sliderules were available in his day, but there were not even HP programmable pocket calculators and certainly no supercomputers, so it was all paper and pencil stuff. In fairness, his mind was surely on bigger things than simple computations. He was astonishingly accurate and precise in what he inferred from his analyses, errors notwithstanding, and the laws that he formulated.

Kepler established that the planets orbiting our Sun describe ellipses—not circles. This is the basis of his first law of planetary motion. From it, comes his second law that a line joining a planet and the Sun sweeps out equal areas during equal intervals of time. It is this law that explains why change in daylength is not constant and why we in the Northern Hemisphere, now at the end of November, are so rapidly and noticeably hurtling toward the long nights of winter.

When I last visited Fordhook Farm outside of Philadelphia, it was mid October. This to me is the best time of fall. The days are still long and may be warm or have just a hint of chill, but the transition is inexorably occurring. When I arrived, tree leaves looked only a little dull; when I left 5 days later, bright colors were undeniably beginning to show.

My purpose for the visit was to help select rare and unusual woody plants for the gardens at Fordhook. There are large shade gardens in progress that will complement those at Heronswood gardens in Washington State, and there is lots of open space for “specimen” plants.

During the time I was there, I and Burpee’s research director scoured nurseries and private arboretums in Pennsylvania and New Jersey. Not everything we found is rare, or even unusual, but some are both, and all are great selections. They are now being planted and should be growing actively next spring.

One plant that particularly caught my attention is Franklinia alatamaha. Sometimes called Franklin tree, but more often called Franklinia, just as the old fashioned term “sweet petunia vine” soon became “petunia”. Franklinia is somewhat available, so not particularly rare, but it is certainly unusual. It has horticultural value, being lovely with fragrant, white, camellia-like flowers that appear from July through fall and shiny dark-green foliage that becomes red with cooler weather in fall. The photographs illustrate the unusual characteristic of flowering while showing fall foliage color. It’s also a bit challenging to grow.

It has historical interest because it was first brought into cultivation in the late 18th century near Philadelphia by an early American farmer turned botanist and was named after Benjamin Franklin,who was a particular friend of the man who discovered it.

Finally, Franklinia has botanical interest. It is native to the USA alone but has apparently been extinct in the wild since 1803. All Franklinia plants in cultivation, worldwide, are derived from a few seeds that were collected from the same small pocket of wild plants during a 27-year period. Therefore, it has an extremely narrow genetic base.

The genus Franklinia is a member of the family Theaceae. Most Theaceae genera have evergreen foliage, but Franklinia and Stewartia, another horticulturally important genus, are exceptions and deciduous. The most familiar genus in the family is Camellia, which is extensively used as an ornamental but is most grown as the source of tea. Franklinia has one species only, alatamaha.

Franklinia will reach about 30 feet high, although two early reports of it in cultivation (1831 and 1846) describe 50-foot trees. It has a pyramidal form when young that becomes more rounded as it ages with lots of stems or trunks developing that lie on the ground and “self-layer” (form roots where touching soil). Two “Franklin trees” growing at Harvard’s Arnold Arboretum are a little more than 100 years old and have become giant spreading things 20 feet high and 30 and 50 feet across. Franklinia grows well in sun to partial shade but will flower best and show better fall color when grown in full sun. It can be somewhat finicky. It does not tolerate clay soil and is not drought tolerant; it does best in well-drained, humus-rich, moist soil that is slightly acid (pH 5–6), and is hardy to USDA hardiness zones 5A through 8B. It is well suited as a border or specimen plant.

The tree was first seen along the Altamaha River in southeast Georgia in 1765 by John Bartram and his son William. John Bartram (1699–1777) was an American botanist, horticulturalist and plant collector. Bartram had no formal botanical training. He traveled widely, usually with his son, throughout the eastern part of what became the USA and to the shores of Lake Ontario identifying and collecting desirable plants. He corresponded and exchanged plant material with the leading botanists of his day, including Carl Linnæus, the Swedish natural philosopher whose work forms the basis of modern scientific nomenclature. Bartram and his son William are credited with introducing into cultivation as many as 200 plant species native to North America. The Bartrams established the first U.S. botanical garden at what is now Philadelphia. The site today includes a botanical garden, meadow, parkland, wetlands, and the original house (see http://www.bartramsgarden.org; verified 19 November 2010).

At that time in 1765, the trees were not in flower and could not be identified. Eleven years later, William returned to the area and collected seed that he cultivated at the nursery at Philadelphia. The Bartrams named the plant using Franklin’s name for the genus and an alternate spelling of the Altamaha River as the specific name. By 1783, William had sent two Franklinia seedlings to Linnæus and had planted two in his own garden. It was these that were surveyed in 1831 and 1846, and presumably, it was from these, or cuttings thereof, that the Franklinia growing at the Arnold Arboretum are descended. The Bartram’s Garden has determined that at least 2000 Franklinia are growing at private and commercial properties as well as public gardens around the world; the oldest of these are at the Arnold Arboretum.

We can only speculate on why Franklinia became extinct in nature. Cultural observations suggest that the Franklinia grows best in more northern climates. If so, the ideal climatic zone is probably different from that of the Altamaha River area. What the Bartrams found in 1765 must surely have been a declining remnant of a once larger population that for whatever reason(s) persisted there. Since the beginning of this current interglacial age about 12,000 years ago when ice sheets began receding, the climate of North America has never been the same; it has been continuously changing. A reasonable possibility is that a changing climate set in motion factors that contributed to the demise of the Franklinia. One of these factors would have been habitat loss and, with that, decreasing genetic fitness as the population collapsed and contracted; another, and perhaps final, factor may have been the introduction of diseases that accompanied the wide-spread cultivation of agronomic crops such as cotton in the neighboring areas. But who knows?

Come see the new gardens and the newly planted Franklinia at Fordhook Farm in the spring. Six 2011 Open Houses are planned for both Fordhook Farm and Heronswood Nursery. Watch the websites for the dates of these events.