BD 502: Yarrow – An Alchemical Organ of the Compost

What Is BD 502?

Yarrow is a common flower—but in biodynamics, it's considered extraordinary. BD 502 is made by harvesting Achillea millefolium, drying its blossoms, and packing them into the bladder of a red deer. This pouch is then hung in the summer sun and later buried in the earth over winter. After transformation, the resulting substance is added to compost piles in minute amounts — but its effect is anything but small.

Biodynamic founder Rudolf Steiner saw something deeply special in this plant:

“Yarrow is indeed a miraculous creation. No doubt every plant is so; but if you afterward look at any other plant, you will take it to heart all the more, what a marvel this yarrow is.” — Rudolf Steiner, quoted in Patricia Smith, Applied Biodynamics, no. 37 (2002), 69.¹ 

How BD 502 Works

BD 502 plays a crucial role in stimulating sulfur processes within the compost and enhancing the soil’s ability to make trace elements available to plants — especially potassium and copper. These are essential for fruit and flower formation and for overall plant immunity.

To prepare BD 502, fresh yarrow flowers are harvested in early summer and carefully cleaned of coarse stem material. The stuffing of the bladder must be done delicately to preserve its integrity:

Our preference at JPI is to have virtually stem-free florets to use in stuffing the bladders. This is most important because the stiff coarse stems, if left attached when being stuffed into the sheath, can puncture the walls of the stag bladder.
– Patricia Smith, Applied Biodynamics, no. 37 (2002), 71.² 

After hanging in the summer sun—where the flowers absorb light and air forces—the bladder is buried in fall and retrieved in spring. The resulting preparation supports the compost’s formative intelligence, bringing coherence and warmth to the heap.

The Spiritual Science of Yarrow

Steiner indicated that yarrow has a special relationship to Venus and Mercury, celestial bodies associated with sensitivity, healing, and metabolic balance. The red deer bladder acts as a resonating vessel, enhancing the prep’s ability to concentrate these forces within the compost.

BD 502 isn't a "material input" — it's a carrier of planetary, elemental, and formative forces. Hugh Courtney emphasized that understanding this demands a new kind of consciousness:

We must exert an effort to grasp what it is that lives in this preparation and how it exerts its influence. In other words, we must do our utmost to understand the preparations, ‘not as substances, but as forces.’
– Hugh J. Courtney, Applied Biodynamics, no. 37 (2002), 83.³

Through this lens, BD 502 becomes not just a biological remedy, but an alchemical mediator—transforming waste into life, and the compost heap into an organ of resurrection.

Footnotes

• Rudolf Steiner, quoted in Patricia Smith, “502: How to Make the Yarrow Preparation,” Applied Biodynamics, no. 37 (2002): 69.
• Patricia Smith, “502: How to Make the Yarrow Preparation,” Applied Biodynamics, no. 37 (2002): 71.
• Hugh J. Courtney, “Achillea millefolium Esoterica,” Applied Biodynamics, no. 37 (2002): 83.