The biodynamic calendar divides each day into one of four types based on the moon's astrological position. Fruit days favor the development of fruit. Flower days favor flowering. Leaf days favor leaf and shoot growth. Root days favor root development. Vineyard operations are scheduled to the day type that matches the operation's goal.
Fruit days
Pruning, harvesting, and bottling are scheduled on fruit days when possible. The theory is that the lunar position supports the fruit's development at these moments, which translates to fewer aromatic disturbances during the operation. Fruit days are also the days biodynamic tasters prefer for evaluating wine.
Flower days
Pruning of grapes destined for white wine production is sometimes scheduled on flower days, on the theory that flower days support aromatic development in the resulting wine. Spraying of compost teas to encourage flowering is also scheduled on these days.
Leaf days
Operations focused on vegetative growth, including cover-crop planting and lees stirring (which redistributes nutrients in the wine and is associated with vegetative character), are scheduled on leaf days. Some biodynamic producers avoid tasting on leaf days, on the theory that the wine shows poorly.
Root days
Subsoiling, root-system care, and the planting of new vines are scheduled on root days. Root days are considered poor days for tasting wine, which biodynamic producers and some sommeliers consciously avoid. Some restaurant programs schedule wine dinners around fruit days for this reason.
The practical reality
Most biodynamic producers cannot strictly schedule every operation to the calendar; weather, labor, and logistics force compromises. The practice is followed where possible, particularly for high-stakes operations like harvest and bottling. The discipline imposes intention on operations that would otherwise be scheduled by default.