The Dutch further introduced to the French a method of sulfuring the wines (known as "allumettes hollandaises") which has the effect of stabilizing the wine and preventing some degree of spoilage. The introduction of new Dutch winemaking techniques helped antiquated methods such as the use of lead fall into disuse. Used since the days of Ancient Rome, lead was used in regions such as Poitou to help sweeten and preserve some of their wines leading to various ailments that collectively were known as the "Poitou colic". By the end of the 17th century, most Poitou winemakers had stopped using lead in their wine production. The Dutch also promoted the plantings of many white wine varieties that were in fashion through Europe. In regions like Muscadet, in the Loire Valley, the Dutch encouraged the planting of Melon de Bourgogne which produced more reliable harvest than the region's red wine varieties. The practice of blending different grape varieties from different areas was also influenced by the Dutch as a means of improving weaker wines or to adapt wines to changing public tastes. When the English developed tastes for stronger sweeter wines, the Dutch were the first to bulk up the Gascon claret wines with the wines of Cahors. Skilled engineers, the Dutch drained the marshy Medoc (left bank) region in the 17th century and began planting the region with vineyards. Prior to this time, Bordeaux's most sought-after wines came from the well-drained soil of the Graves region including the estate of Chateau Haut-Brion. By the end of the 17th century, with the aid of the Dutch, the future First Growth estates of Chateau Lafite, Latour and Margaux were planted and already starting to get notice abroad. While there have been theories put forth that the Christian Church "saved" viticulture in France following the fall of the Roman Empire, the Germanic tribes that invaded the region were known to be fond of wine themselves leaving little evidence that viticulture and winemaking needed to be "saved" during this period. The Church, however, did become one of the most prominent and influential forces in French winemaking during the medieval period due to their vast holdings of vineyard lands. The Merovingian period of Frankish rule saw the early seeds of monastic influence on French wine when Guntram, Clovis' grandson, gave a vineyard to the abbey of St. Benignus at Dijon.