Dear Curious Cork,
If you listen to Mike Benzinger, he describes biodynamics as an ‘energy management system,’ which still sounds confusing.
Biodynamics is rooted in the work of an Austrian philosopher named Rudolph Steiner. It’s a holistic farming practice that divides winemaking and viticultural tasks based on a special biodynamic calendar. The days of the year are categorized into four groups: Fruit Days (best for harvesting grapes), Root Days (ideal for pruning), Flower Days (days to leave the vineyard alone), and Leaf Days (optimal for watering plants). These days correspond to the four classic elements: earth, fire, air, and water. The days division is based on the lunar calendar and how it affects water in the plant. The idea is that as the moon gets larger (waxes) the water/sap is moving higher in the plant- thus it would be negative to prune the plant at that point. A smaller moon would be better. There are beliefs around what stage the moon should be at for racking and bottling. Some wine enthusiasts argue that wines exhibit different facets of their character on different days. Flower and Fruit days are believed to showcase the fruit of wines at their best, while Leaf and Root days are considered less enjoyable. Root days showing more minerality while leaf days show the vegetal notes in a wine.
In addition to this quirky calendar, other aspects of certified biodynamic wine growing involve avoiding chemicals, commercial yeasts, and limiting sulfites to only up to 100 parts per million. But perhaps one of the weirdest aspects of biodynamic farming is how fertilization is done. Cow horns are filled with a special compost preparation and buried in the vineyard. These special preparations may include ingredients like yarrow blossoms, chamomile (a natural antiseptic), or stinging nettles (a natural cleanser). While there is plenty of solid science behind the biodynamic movement – there are also some mystical belief elements that don’t always make the most sense. Remember that most grape growers are farmers. And most farmers don’t check their horoscope before heading out to prune the vines. I have spoken with more farmers who lean into the idea of pick and choosing biodynamic practices. ‘Demeter’ is the only group I know of that certifies farms as biodynamic and I don’t seem their labeling frequently. Biodynamic is like ‘natural’ or ‘farm-fresh’ – it indicates but isn’t a legally protected term.
Personally, I’m not entirely sure what to believe… I suppose I need to do some more tasting to form an opinion.
Care to join me? 
