Drying, and keeping a preparation good

Two processes decide whether a dried herb is worth anything in six months: how it was dried, and how it is stored. Both are governed by the same chemistry — volatiles evaporate, phenolics oxidise, and water enables microbial growth and hydrolysis.

Drying. The target is below about 10% moisture for leaf and 12% for root, at which point the material snaps rather than bends. Two rules:

• Heat drives off the volatile fraction. The compounds responsible for the smell of
• Shade, not sun. Sunlight degrades chlorophyll and many phenolics, and the colour loss

Bundles or screens. Hanging small bundles in a dark, dry, ventilated room works well for stemmed herbs. Screens or trays work better for petals, leaf picked off the stem, and anything that would mould in a bundle. Either way, air must move — still air traps moisture in the middle of a bundle, and the middle of a bundle is where mould starts. Turn material daily in the first few days.

Harvest timing changes the chemistry, not just the yield. Secondary metabolite content peaks at a particular stage for each plant and part — commonly just before flowering for leaf, at full flower for flower, and in late autumn for root. Harvesting a leaf at the wrong stage gives a bigger pile of weaker material. Two practical markers: leaf before the plant flowers, flowers at their peak and in dry weather, and root after the tops have died back.

Storage. Four enemies, each with a specific counter:

| Enemy | Effect | Counter | |---|---|---| | Light | Degrades phenolics, bleaches | Amber or opaque glass, or a dark cupboard | | Oxygen | Oxidises oils and aromatics | Fill the jar high; minimise headspace | | Heat | Accelerates every degradation | Cool, stable temperature | | Moisture | Mould, hydrolysis, loss of potency | Absolutely dry herb in a sealed jar |

A sealed jar of genuinely dry herb in a dark cupboard keeps a useful phenolic content for 12-18 months; whole leaf keeps longer than powder because less surface is exposed. Powdered herb loses potency much faster than whole — one of the better arguments for storing leaf and grinding it as you use it. Roots and barks keep 2-3 years; flowers and volatile leaf 6-12 months.

The label is part of the method. Plant, part, date of harvest or purchase, and how it was dried. Without those, the second year's jar is an anonymous brown powder and the honest position is to throw it out.

Tests worth doing. Crush a leaf and smell it — if it is odourless it is spent. Look for a colour change toward brown or grey. Feel for any softness, which means moisture. Any mould, any musty smell, any clumping means discard: mycotoxins are not removed by washing or heating.