Revisiting the Greenhouse

Doing field archaeology during a summer heat wave, when temperatures exceed one hundred degrees, when you are gulping down half a liter of water every fifteen minutes, when the air is so humid that it is heavy, when you feel the mosquitoes buzzing around you, is…fun! These past few weeks, whenever Washington afforded me several consecutive days of clear skies, I have been focused on completing the excavation of the old pit greenhouse located near the vegetable garden, concentrating on two important tasks: excavating three 5 x 3′ test units in order to identify the base of the greenhouse, the way it was constructed (and de-constructed), and the type of soil it was built on; and clearing the profiles, in order to understand the stratigraphy of the area. Stratigraphy is a term borrowed from geology, and in archaeology it refers to the layers of both natural and cultural features. As a general rule, the more superficial layers are more recent and the deeper layers are older. Studying the stratigraphy of a site is useful to reconstruct the “life story” of the greenhouse: how it was built, how it was abandoned, and what has happened since then. In this case, the profile indicated that the greenhouse was built on very hard, rocky greenish-brown soil, and part of the floor may have been compacted clayish brown soil, an adequate foundation for this type of structure. “Reading” the layers and the physical remains of the greenhouse also revealed the imprint of demolished walls, and in one of the units we found a layer of broken brick under the central concrete corridor. These bricks would have served to reinforce and stabilize the foundations of the concrete floor.

Back in the Greenhouse

Back in the Greenhouse


Image 2

Reading the stratigraphy of the greenhouse: a floor made of compacted earth, followed by the concrete walls of the greenhouse. After it was abandoned, the greenhouse was filled in with earth and fill, in which we found the debris from the demolition process. Finally, a lush layer of fast-growing grass as the most recent layer. 

Unit two before exxcavation

Unit two before exxcavation



Unit 2 at the end of the excavation. Notice the concrete floor (left), the imprint of long-demolished walls on both the floor and the back walls (centre), and the hard, rocky, greenish soil which served as the foundation for the greenhouse.



Image 2, showing the remains of broken bricks under the concrete floor corridor of the greenhouse.



The back of the greenhouse, showing the concrete foundations and imprint of brick walls.

So far, we have been able to reveal a structure far more complex than what we initially believed, mainly due to the discovery of a concrete foundation located at a higher level than the original pit greenhouse, with the remains of a brick wall. Our very preliminary idea, based on the evidence, is that the greenhouse may have been built on two levels, taking advantage of the slope of the terrain.

Although the actual process of excavation yields plenty of information, it was the in the documentation through photography and ground plans that more details emerged, along with more questions and theories of how the greenhouse worked and what was its form. In this case, the plan of the excavation area was especially important since we have not been able to find the original plan for the greenhouse. However, even if we did have the original plan, it does happen that architectural plans and blueprints are not always absolutely accurate reflections of what is eventually built, and they do not include later modifications to the structure. Now that the excavation is complete, a potential next step could be to compare the floor plan of the excavated greenhouse with those of other, contemporary and similar structures; determining which areas were roofed and which were exposed; examine what was the relationship between the two main spaces we identified; and if we are looking at a structure that was built all at once or in stages. By understanding how the old greenhouse worked (and what did not…), we hope to obtain information that will be useful in the potential reconstruction of the greenhouse.

Please Do Not Climb The Lions, and other approaches to conservation and preservation

Part of my research has also focused on studying how nearby and similar parks and gardens, both public and private, approach the issue of conservation, and how do their approaches compare to that of Dumbarton Oaks gardens. In the United States, the Secretary of the Interior has issued a series of guidelines regarding the treatment and management of historic buildings, places and landscapes, and describes four main options: preservation (sustaining the historic form, materials and design), rehabilitation (adapting a historic building/landscape to new use, while still retaining the imprint and identifying features related to its old use; an example being the conversion of old industrial lofts to apartments and stores), reconstruction and restoration (choosing a period of significance, then removing all features that do not belong to this period; think Mount Vernon). One of the main problems with these options is that, with the exception of rehabilitation, all assume that the main value and significance of historic places lies in the past, which often restricts flexibility and the nature of places to change and adapt with time. For instance, I was surprised to read that there was actually a requirement to state a “period of significance” in which the place “acquired” its significance and value. This ignores the fact that places are not just discrete events and moments in time, but a continuum. Think, for instance, of an iconic place like the Lincoln monument, which has witnessed many significant moments that have shaped the way this place is perceived and remembered. It is very likely that this monument will continue to inspire and be the stage for more significant, perhaps even history-changing events in the future. How could we pick just one period of significance?

It is my belief that some of the most successful and valued places are those that preserve their past while adding layers of modernity, creativity and even whimsy. One of the historic places I researched got around this restriction by establishing a “period of significance” which spanned thousands of years, from the prehistoric period all the way to the time when the site was adapted for visitors in the mid-20th century. In this way the curators of this place thus recognized the futility of trying to decide what was “the” most significant period, and emphasized that historic places are made up of many different layers. For instance, is it possible to choose just one “period of significance” for Dumbarton Oaks, considering the number of people who influenced and shaped its design over the years, and considering that even today we still shape this place by the way we use it, the way we see it, the ways we value it? Over lunchtime (ice-cream sandwiches with watermelon, obviously) a fellow once told me that “conservation encourages restraint”, of making sure memorable places remain recognizable, but not static and unchangeable. Conservation is more about curating, about preserving the many layers of the past while adding more layers of interest. What would happen if one day we went for a quiet morning stroll in the gardens and found Lover’s Lane pool filled with pink rubber ducks? Wouldn’t we suddenly see the place differently?

Please do not climb on the lions! Preservation policies at Hillwood estate.

Please do not climb on the lions! Preservation policies at Hillwood estate.



Researching how the public uses and perceives a historic park by using rigorous hands-on methods (Montrose Park, Georgetown)

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