Overview
Consisting of south by southwest facing slopes on the Langoiran limestone plateau, Biac’s terroir reflects the countless slow changes of the Garonne riverbed over centuries. The 9-hectare vineyard reveals an astonishing soil variety from asteriated limestone dating from the Oligocene Period to gravelly sediment from the Quaternary Period.
A detailed survey of the soil undertaken in 2007 concluded that some restructuring of the vineyard was necessary and a 12-year plan was established.
As a result, grape varieties, clones and rootstocks are being adapted to each part of this unique and remarkably diverse terroir in order to produce wines of the highest quality.
The steepness of the hills provides excellent drainage for the vines. The high proportion of gravel (meagre soil) on the upper part of the slope is ideal for growing high quality Cabernet Sauvignon, whereas the clay limestone soil further down suits the Cabernet Franc beautifully. The adjoining silt and sand plots offer optimal growing conditions not only for Merlot grapes but also for the Semillon and Sauvignon Blanc varietals.
Merlot vines also prosper at the bottom of the hills where the relatively shallow clay-limestone soil lies on a platform of asteriated limestone. The survey equally revealed that the Petit Verdot would thrive in the upper part of the property and it was therefore introduced on the property in 2008. This wide soil diversity enables the production of wines of rare complexity.
The topography of Château Biac is a great asset to the vineyard: the slopes provide excellent natural drainage which is essential during rainy periods and of crucial importance during the ripening of the grapes. The south by southwest sun exposure is optimized by the natural incline of the hills. Good ventilation and humidity provided by the Garonne River flowing below Biac protect the vines from unwelcomed spring frosts and excessive heat during the summer.
All these natural factors make of Biac an outstanding terroir, whose potential is regularly analyzed and rethought with a view to exploiting it to the maximum.
The Terroir of Chateau Biac
The terroir of Biac is truly unique in the Bordeaux region.
To determine the make-up of a terroir, one studies its principal components, namely soil composition and climate patterns.
As an overview, one can describe the Biac terroir as an astonishing variety of soils coupled with a very well-regulated climate.
1. Soils
The amphitheatre shape of Biac has the particularity of being made of several soil topologies:
Towards the top: gravel laden soils very similar to those of the Medoc lie side by side with pure clay typically found in the right bank.
Towards the lower part: chalky clay similar to that of St Emilion
In between, silt infused sands very much like parts of Pomerol
2. Climate
- The close proximity of the Garonne River allows an important regularisation of the climate and protects the vineyard from spring frost. There is an old saying: “vineyards overlooking the Gironde are shielded from the frost”. The same can be said for the Garonne River and the vineyards bordering it.
- Extreme temperatures are tempered by the river’s soft air: by providing this moderate influence, the climate is more balanced.
- The relief:
- The South facing slope is ideal not only for maximising sun exposure, but also for natural drainage of rainwater.
3. The Human Hand
As part of the composition of a terroir, one must also consider the impact of the human hand. In the presence of such an exceptional soil diversity, varietals must be selected with precision and care. Respect for this very precious terroir must be exercised: homogenous soils are far easier to manage.