While most of Virginia resides firmly in the USDA hardiness zone 7a today which has a shorter winter and a warmer summer; 200 years ago there was a much colder climate in the area of Monticello and particularly at the elevation of this “little mountain”. The trick, I was to learn, was the fact that he created the garden plateau as well as the trellised gardens below. By creating the plateau, he created a space for the sun’s warmth and light to hit the plants all day long (positioning the plateau from east to West). He enhanced the climate of the lower gardens by taking the large rocks and stones from the excavation of the upper plateau to create a rock wall to hold back the plateaued earth. The rocks absorb the heat from the sun and reflect that heat to the grape arbors and fruit trees below. This was way ahead of the time that Jefferson lived, particularly in the new United States. While microclimates have always existed and were definitely exploited by primitive agricultural societies, this knowledge was lost during the world’s rush to industrialize.
Creating micro-climates in our gardens doesn’t have to take an army of workers (thank goodness), you can add medium to large rocks in certain beds like I have in my herb garden. You can also locate the beds specifically to capture surrounding heat (near a house or other large structure, in full sun, in part shade, etc.). By creating climates, you can grow certain plants that may not be specifically designed for your hardiness zone.
To learn what your zone is and what plants do best in it and the surrounding zones, visit http://www.usna.usda.gov/Hardzone/ushzmap.html