Yarrow is a flowering plant widely used in traditional practices for its beneficial properties. These effects are attributed to various volatile oils and complex chemical compounds present in the flowers and leaves. To preserve the maximum concentration of these delicate chemical components, drying the herb correctly is necessary. Proper processing ensures the plant material retains its aromatic qualities and therapeutic strength.
Optimal Harvesting and Preparation
Harvesting yarrow when its chemical profile is at its peak helps maximize potency. The best time to gather the plant is when the flower heads are fully open, typically during the mid-summer months. Cutting the aerial parts should be done on a dry, sunny day.
To prevent mold and degradation, harvest mid-morning after any dew has evaporated from the foliage. Immediately after cutting, gently shake the plant material to dislodge insects or loose dirt, and remove any damaged pieces. Rinsing yarrow is not recommended, as the added moisture increases the risk of mold during drying.
For air drying, gather the stems into small bundles, securing them loosely with twine or a rubber band. The bundles must be small enough to allow for unrestricted air circulation through the center of the stalks.
Traditional Air Drying Methods
The traditional method of air drying provides the most gentle preservation. Volatile oils can be degraded by heat and direct sunlight, so the drying location must be dark, cool, and possess low humidity.
Good air circulation is necessary to wick moisture away from the plant material. Hanging the prepared bundles upside down aids moisture removal. Suspending the bundles from rafters or lines ensures they do not touch any walls or other surfaces.
An ideal temperature range for air drying is between 60 to 75 degrees Fahrenheit (15–24 degrees Celsius). Higher temperatures risk cooking the herb, while cooler temperatures slow moisture removal and increase the chance of mold growth.
Yarrow requires anywhere from one to three weeks to dry completely, depending on local humidity and stem thickness. Monitoring the process daily is advisable, especially during the first week when moisture loss is highest. Consistent temperature and airflow are more important than achieving any specific single temperature point.
Testing for complete dryness is a tactile process. The stems should snap cleanly when bent, and the leaves and flowers should crumble easily when rubbed. If the material feels pliable or slightly soft, it contains too much moisture for long-term preservation.
Accelerated Drying Techniques
When time constraints prevent traditional air drying, mechanical aids offer quicker alternatives, though often at the expense of some volatile oil content. A food dehydrator provides a controlled, low-heat environment that accelerates moisture removal. Spreading the yarrow flowers and leaves in a single layer across the trays ensures even exposure to the circulating warm air.
Set the temperature to the lowest possible setting, between 95 and 105 degrees Fahrenheit (35–40 degrees Celsius), to minimize heat damage. The process takes between four and twelve hours, and the herb is ready when it is brittle and dry. Using a conventional oven is possible if it maintains a temperature below 150 degrees Fahrenheit (65 degrees Celsius), but requires constant attention to prevent scorching.
Storing Dried Yarrow for Maximum Potency
Once completely dry, yarrow should be processed immediately for storage to prevent reabsorption of ambient moisture. Remove the dried flowers and leaves from the tougher stems, which contain fewer desired compounds. Crumble the material lightly and avoid powdering it, as this increases the surface area exposed to oxygen, leading to quicker degradation.
The processed herb must be stored in an airtight container to protect it from moisture and air. Placing the container in a cool, dark location, away from stoves or windows, prevents degradation caused by light and heat. Properly dried and stored yarrow retains its potency for approximately one year.