Six Compost Preparations and Their Plants

The six compost preparations are made from yarrow, chamomile, stinging nettle, oak bark, dandelion and valerian. Each plant carries a different job in a heap, and the way it is gathered and stored decides whether it still does that job. A preparation made from flowers picked in full sun and dried fast behaves differently from one made from the same flowers wilted in a sack. A walker who follows the named oaks of the Tronçais forest sees the same long view applied to trees, where a single species and its management decide what the ground beneath it becomes.

Which plants are used for the compost preparations?

Six plants supply the six preparations, and each is paired with a different organ or substance before it goes into the heap.

• Yarrow (Achillea millefolium), preparation 502. The flowers are stuffed into a stag's bladder and hung in the sun through summer, then buried in earth over winter.
• Chamomile (Matricaria chamomilla), preparation 503. The flowers are packed into a cow's small intestine and buried in rich soil.
• Stinging nettle (Urtica dioica), preparation 504. The whole plant, stems and leaves together, is buried in earth for a year, often wrapped in peat or in a casing of clay.
• Oak bark (Quercus robur), preparation 505. The bark is ground to a powder, placed in the skull of a domestic animal, and buried in a watery, rain-fed spot.
• Dandelion (Taraxacum officinale), preparation 506. The flowers are pressed into a cow's mesentery and buried in earth over winter.
• Valerian (Valeriana officinalis), preparation 507. The flowers are pressed for their juice, which is diluted and sprayed on the heap rather than buried.

The pairing is not decorative. The bladder, intestine, skull and mesentery each hold moisture and air in a different way, and each plant is asked to work inside that particular envelope. Anyone who has watched a forest edge change from one decade to the next knows how much a single species can alter a site, and the same principle holds at the scale of a compost heap.

How is each one gathered and dried?

Gathering follows the plant, not the calendar alone. The rule is to take the part the preparation calls for at the moment it is most alive.

Yarrow and chamomile are picked as flowers, in dry weather, in the morning after the dew has lifted. Dandelion is picked the same way, in full flower, before the heads close. Nettle is cut before it sets seed, when the stems are still tender. Oak bark is stripped from felled or pruned wood in spring, when the sap is moving and the bark lifts cleanly from the timber. Valerian is cut when the flower heads are fully open, and the juice is pressed soon after.

Drying is where many batches are lost. Flowers are spread thin in a shaded, airy place, never piled, because a heap of damp blossoms heats and ferments within hours. Nettle is dried whole or used fresh, depending on the method. Oak bark is dried slowly and then ground, since bark that still holds moisture will mould in storage. Valerian is the exception: it is not dried at all, but pressed and the juice kept in a dark bottle.

The test is simple. A dried flower should crumble between the fingers and still smell of the plant. If it smells of hay or of nothing, the volatile oils are gone and the preparation will be weak.

How is each one stored through the winter?

Storage protects what the drying preserved. The buried preparations spend their winter in the ground, which is the storage. The ones that are not buried need a different arrangement.

Dried flowers and powdered bark go into glass jars with tight lids, kept in the dark at a steady cool temperature. Paper bags are a poor choice for long storage, because they breathe and take up moisture from the air. Valerian juice is kept in a small dark bottle, filled to the top to limit contact with air, and stored away from light and heat.

A cellar, a cool cupboard or a north-facing shelf all work. The enemy is fluctuation: a jar that warms and cools repeatedly will condense moisture on the inside of the glass. Labelling matters more than it seems, because dried chamomile and dried yarrow look similar in a jar by February, and a mixed batch is a wasted batch.

What does each preparation contribute to a heap?

Each preparation is asked to do something different, and the traditional descriptions are best read as roles rather than as chemical claims.

Yarrow is associated with the uptake of trace elements and with the heap's relationship to light and air. Chamomile is linked to the stabilisation of nitrogen and to a calm, steady breakdown. Nettle is described as bringing order and stimulation, particularly where the heap is cold or slow. Oak bark is tied to protection against disease and to the balance of the heap in wet conditions. Dandelion is associated with the flow of nutrients and with the relationship between the heap and the soil beneath it. Valerian is linked to warmth and to the sealing of the heap, which is why it is sprayed on the surface rather than buried.

Does the way a plant is gathered change what it does?

It does, and this is the part most often skipped. A preparation is not a substance with a fixed strength. It is a plant material that has been handled in a particular way, and the handling is part of the preparation.

Flowers picked after rain, or in the heat of late afternoon, carry different moisture and different oils. Bark stripped in autumn, when it clings to the wood, tears and brings splinters of timber with it. Nettle cut after seeding has already spent much of what it had. Valerian pressed from wilted heads gives less juice and a duller smell.

Storage continues the same logic. A jar opened every week takes up moisture and loses aroma. A buried preparation left in waterlogged ground for too long will rot rather than transform. The traditional timings, a summer in the bladder, a winter in the earth, a year for nettle, are not arbitrary. They place the material in conditions where the transformation can happen at the pace the plant allows.

A practical order of work

The six preparations can be made by one person across a year without special equipment. The sequence that works is to start with the plants that need the longest burial, nettle first, then the flowers that go into the bladder, intestine and mesentery in summer, then the bark in spring, and the valerian last, since its juice is used fresh and does not need a season in the ground.

What decides the result is not the number of preparations made but the condition of each one when it goes into the heap. A small batch of well-dried, well-stored material will do more than a large batch of flowers that were piled wet and forgotten. The plants do the work. The gatherer's job is to keep them able to do it.