Late 18th- to Early 19th- Century Flowerpots at The Woodlands

FLOWERPOTS—earthenware pots that are built to contain plants, not to be confused with ornamental urns—have a long history that dates to the Romans, if not earlier. However, they were not produced in great quantities until the early 18th century and only mass-produced from the second half of 19th century onwards. As utilitarian objects made specifically for horticultural use, they are found in the archaeological record in connection with historical gardens, nurseries, and greenhouses. Despite their ubiquity at historical garden sites, their production remains surprisingly unexplored.

Fit For Purpose

Flowerpots are easily recognizable by their straight- sided walls, draining hole at the center of the base, and undecorated exterior. Most were left unglazed as they are today to maintain porosity, allowing for proper water evaporation and oxygenation of the plant roots. Low-cost containers that can be stacked for storing when unused, flowerpots allow plants to be easily moved indoors and outdoors. They are designed to fit the various root systems of plants and manufactured in sizes reflecting each stage of plant development: shallow seed pans for starting seeds, tiny thumb pots or thimbles for seedlings and propagation, mid-sized pots for re-potting, tall “long Toms” for deep-rooted plants or bulbs, and saucers or trays for collecting drained water. Some flowerpots, for example those with a double rim, could accommodate a glass bell that was placed over the plant to protect it from the elements. These “garden utensils,” as Loudon calls them in his 1822 Encyclopaedia of Gardeningⁱ, were standardized and graded for easy re-potting of plants into incrementally larger pots during the growing cycle.

Recent archaeological excavations at The Woodlands, Philadelphia—the estate and home of William Hamilton from 1767 to 1813—have yielded a number of garden-related artifacts. The flowerpots found during excavation offered an opportunity to study a group of artifacts commonly thought to have been produced in the Philadelphia area, but which had not yet been analyzed scientifically. One of the aims of this preliminary study was to characterize the differences in raw materials and firing technology between The Woodlands’ flowerpots, glazed redware, and bricks. Ultimately, we were interested in distinguishing the products of different local or regional potteries based on the mineralogy and technology of the flowerpots.

The Pottery Trade in Philadelphia

With abundant iron-rich clay deposits available locally, the result of extensive post-glacial deposition in the area by the Delaware River, Philadelphia has a long history of ceramic production and brickmaking. The production of red earthenware in the area dates to the city’s earliest years as an English settlement in the 17th century. The clay deposits were also exploited by local brickworks, and, by 1794, there were 14 brick kilns in Old City, attesting to the quality and abundance of clay deposits for brickmakingⁱⁱ.

By the mid-18th century, Philadelphia’s rapid population growth and demand for earthenware and stoneware saw an increase in potters operating in the city. The late 18th- to early 19th-century potteries or “pot-houses,” as they were referred to in historical documents, were equipped with a potter’s wheel, clay mills, glaze mills, and an assortment of potter’s tools. While clay was listed in inventories, there is no information on the sources of clay used by potters; we may assume, given the abundant local deposits, that both brickmakers and potters—who shared close ties and witnessed each other’s wills and deeds—may have shared the same sources of clayⁱⁱⁱ. Clay for pottery would have required additional steps of refinement.

In the first half of the 19th century, the organization of redware production shifted from family workshops to larger factories. By 1850, this change was linked to the process of industrialization when mold-made ceramics using mechanized processes resulted in the proliferation of utilitarian products^iv.

William Hamilton’s Greenhouse

William Hamilton inherited The Woodlands property in 1766 and made it his permanent home. At the time, The Woodlands was a large estate located in a rural setting to the west of Philadelphia along the western bank of the Schuylkill River. Hamilton was interested in English-style landscape gardening and became a well-known botanist and collector of rare and exotic plants during his life. Hamilton’s 1813 obituary summarizes well his passion: “The study of botany was the principal amusement of his life.” Not surprisingly, one of the auxiliary structures at The Woodlands built by Hamilton was a large greenhouse whose construction began in 1792.

According to historical documents, the greenhouse was 140 feet long with a two-story core flanked by one-story hothouses. It held Hamilton’s extensive collection of 6,000 to 10,000 plants^v. The greenhouse is no longer standing, but it could have looked similar to the greenhouse complex that was constructed at the Elgin Botanic Gardens in New York. (For more on Hamilton’s greenhouse, see Herrmann’s article in this issue.) The Elgin complex was built in 1803 after plans of Hamilton’s Greenhouse. Sources from the period, including personal letters and visitors’ accounts, state that The Woodlands greenhouse was often considered equal to those in Europe^vi.

Seed packets found between joists in the attic of the Mansion give an interesting glimpse of the type of plants Hamilton was growing on his estate. (For more on the seed packets, see Peck’s article in this issue.) Hamilton’s extensive botanical collection would have required a considerable number of horticultural containers, some of which have been recently found in the limited excavations near the probable location of the greenhouse complex. In his letters to his private secretary, Benjamin H. Smith, William Hamilton mentions several plant species that were kept in flowerpots inside The Woodlands Greenhouse, particularly during severe weather: magnolias, bayberry, and roses, which he potted himself. He even instructed his gardener to mark certain flowerpots filled with exotic plants so that he could easily identify them when he returned from his lengthy travels.

William Hamilton was a contemporary and neighbor of William Bartram. Both men shared a passion for botany. Excavations of the historical greenhouses at Bartram’s Garden, about a mile further south along the Schuylkill, have yielded thousands of fragments of hand-thrown redware flowerpots dating to the first half of the 19th century^vii. It is possible that both Hamilton and Bartram obtained at least some of their pots from the same local potters.

What is Ceramic Petrography?

Ceramic petrography is an analytical technique that uses polarized light microscopy to examine the mineralogical composition and microstructure of ceramic thin sections (cross-sections of flowerpots). It is like “fingerprinting” ceramic objects, i.e., identifying where they were made by matching the mineralogy of the clay paste to specific geological areas around the world. Ceramic petrography also provides invaluable technological data on manufacturing processes and firing practices.

The Woodlands Flowerpots Under the Microscope

We assume that a range of pots was on hand in Hamilton’s greenhouse. The excavations found hand- thrown flowerpots of various dimensions. The presence of very small starter pots for sprouting seeds found in the excavations and in the attic of The Woodlands Mansion show that plants were not only maintained but that propagation activities were taking place.

The Woodlands ceramic fragments selected for petrographic analysis were taken from very small seed pots and medium-sized flowerpots. Additionally, a glazed redware pot and two bricks from the greenhouse excavation were sampled. For comparative purposes only, we also characterized a modern, mold-made flowerpot and a vintage flowerpot produced by Richard Sankey and Son Ltd, a well-known English flowerpot manufacturer which produced up to 60,000 pots a day in the early 20th century.

Our analyses showed that The Woodlands flowerpots and glazed redware samples are made of clay paste that is orangey red, porous, and contains inclusions that can only be seen at higher magnifications. Ridges and grooves on the inner surface of the walls attest to the use of a pottery wheel in their production, while
the outer surface is smoothed with no other treatment. After we prepared the samples as ceramic thin sections in the lab, they were observed using a polarizing light microscope. At the microscopic scale, the similarity between samples continues. The ceramic thin sections are characterized by abundant inclusions of fine sand-sized to silt-sized quartz, plagioclase feldspars, polycrystalline quartz, muscovite, and biotite set in a red to orangey-brown, iron-rich clay groundmass. The mineralogy is so fine-grained that it is not very diagnostic for sourcing, but it does reflect the geological landscape in and around Philadelphia. The metamorphic rocks of the Wissahickon Geological Formation include quartzite and schists whose mineral composition falls in the same suite of minerals found in The Woodlands flowerpot thin sections.

Petrography has also highlighted some slight differences in the optical activity of the clay groundmass, especially between the flowerpots and the glazed redware pot: the latter is better fired as evidenced by the partially vitrified groundmass. This is not surprising as glazed ware is often twice fired in a kiln for a better fit between ceramic body and glaze. The flowerpots were homogeneously fired in an oxygen-rich firing atmosphere at temperatures lower than 1000°C. This firing practice fits with what we know of 18th-century flowerpots, which were fired no higher than 980°C^viii. The larger flowerpot sampled has a slight gray core, suggesting a short firing. Pores and elongated inclusions are oriented obliquely to the pot’s wall, attesting to the use of a fast wheel for the forming of the pot.

The two brick fragments used similar iron-rich clays but show different processes in clay preparation and firing temperatures. They are characterized by abundant, fine sand-sized, angular, monocrystalline quartz set in a dark red optically inactive groundmass. These bricks were fired at higher temperatures (above 1000oC), which vitrified the clay groundmass and thermally decomposed (i.e., melted) the silt-size mica minerals.

Getting to the “Root of the Matter”

Where did Hamilton obtain his flowerpots? At this early point in the project, we cannot be sure. In the late 18th and early 19th century, more than a dozen potters were active in Philadelphia, selling their utilitarian wares, including flowerpots, to local customers. Their products were mostly unadorned, unsigned and standardized, creating a homogenous group of redware pots very similar to others manufactured on the eastern coast of the United States and in England.

Research on flowerpots from other colonial cities, for example at Colonial Williamsburg and Québec City, show the use of local, regional, and imported flowerpots^ix. Did Hamilton commission flowerpots from a specific Philadelphia-based potter, or did he acquire flowerpots from different potteries in and around the city? One could also ask if some of his plants arrived in earthenware containers, or if he acquired imported pots, increasing the diversity of the potting traditions found at the greenhouse. To really get to the root of the matter will require further excavations to reveal the site of Hamilton’s Greenhouse, in conjunction with a comprehensive analytical program for the study of flowerpots from The Woodlands and other contemporaneous greenhouses, such as Bartram’s Garden. The results will enable us to explore more deeply the configuration of horticultural activities in early 19th- century Philadelphia.

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ACKNOWLEDGEMENTS

We would like to thank The Woodlands and Jessica Baumert, Executive Director of The Woodlands, for permission to take samples.

Marie-Claude Boileau, Ph.D., is the Director of the Center for the Analysis of Archaeological Materials and Teaching Specialist for Ceramics. Justin Lynch and Yuyang Wang were M.A. students at Penn when they worked on this material. Justin is currently with AECOM in Atlanta as an Architectural Historian. Yuyang
is a Ph.D. candidate in Archaeology at Stanford University.

ENDNOTES

ⁱ Loudon, J.C. An encyclopaedia of gardening: comprising the theory and practice of horticulture, floriculture, arboriculture and landscape-gardening including all the latest improvements. London: Longman, Hurst, Rees, Orme, and Brown, 1822.↪

ⁱⁱ Gillingham, H.E. “Some early brickmakers of Philadelphia.” The Pennsylvania Magazine of History and Biography, 1929 (53[1]): 1–27.↪

ⁱⁱⁱ Bower, B.A. “The pottery-making trade in colonial Philadelphia: the growth of an early urban industry.” In Domestic pottery of the northeastern United States 1625–1850, edited by S. Peabody Turnbaugh, pp. 265–284. Orlando: Academic Press Inc, 1985.↪

^iv Myers, S.H. “Handcraft to industry: Philadelphia ceramics in the first half of the Nineteenth century.” Smithsonian Studies in History and Technology, 1980 (43): 1–117.
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^v Chesney, S. “The root of the matter: Searching for Willian Hamilton’s greenhouse at The Woodlands estate, Philadelphia, Pennsylvania.” In Historical Archaeology of the Delaware Valley, 1600–1850, edited by R. Veit and D. Orr, pp. 273–296. Knoxville: University of Tennessee Press, 2014.
Stetson, S.P. “William Hamilton and his Woodlands”. The Pennsylvania Magazine of History and Biography, 1949 (73[1]): 26–33.↪

^vi Jacobs, J.A. “William Hamilton at the Woodlands: A construction of refinement in Philadelphia.” The Pennsylvania Magazine of History and Biography 2006 (130[2]): 181–209.↪

^vii Fry, J.T. “Archaeological research at historic Bartram’s Garden.” Bartram Broadside, Summer: 1–14. Philadelphia: The John Bartram Association, 1998.↪

^viii Buxton, B.W. “The making of a flowerpot.” In The art of the potter, edited by D. Stradling and J.G. Stradling, pp. 148–149. New York: Main Street/Universe Books, 1977.↪

^ix Duguay, G. “Utensils for the growing of plants.” In Under the boardwalk in Québec City, edited by P. Beaudet, pp. 109–121. Montréal: Guernica Editions Inc., 1990.↪