Mullein is a biennial plant, meaning it lives for two years, and each part of the plant has a different ideal harvest window. Leaves can be picked throughout the growing season, flowers are gathered individually as they bloom in the second year, and roots are best dug up before the flower stalk appears. Knowing which year your plant is in makes all the difference.
First Year vs. Second Year Plants
Before you harvest anything, you need to identify what stage your mullein is in. In its first year, mullein stays low to the ground as a rosette of large, fuzzy leaves. These leaves are bluish to gray-green, roughly a foot long and four inches wide, and covered in soft, woolly hairs. There’s no central stalk yet.
In the second year, the plant sends up a single unbranched stem that can exceed six and a half feet tall. The leaves along this stalk are smaller than the basal rosette leaves, arranged alternately, and slightly winged where they attach to the stem. A dense spike of yellow flowers forms at the top. Once you can tell which year you’re looking at, you can decide what to harvest and when.
Harvesting Leaves
Mullein leaves are the most forgiving part to harvest because you have a wide window. First-year rosette leaves are perfectly good to pick, and many foragers prefer them because they’re large and haven’t yet diverted energy into flowering. In the second year, you can still harvest leaves from the stalk, but the biggest, most robust leaves come from that first-year rosette.
Pick leaves in summer or whenever the plant is actively growing and healthy looking. The most important rule is to harvest when the leaves are completely dry, with no dew or rain on them. Morning moisture trapped in all that fuzz creates ideal conditions for mold later during drying. Wait until mid-morning or early afternoon on a dry day. Choose leaves that look clean and vibrant, avoiding any that are yellowed, spotted, or insect-damaged.
One thing to keep in mind: mullein’s fine hairs can irritate skin on contact. If you’re handling a large batch, lightweight gloves help. The irritation is mild for most people, but it’s worth knowing before you spend an hour picking leaves barehanded.
Harvesting Flowers
Mullein flowers only appear in the second year, blooming a few at a time along that tall central spike. This is what makes flower harvesting a bit tedious. Rather than cutting the whole stalk, you pick individual flowers as they open. Each small yellow blossom lasts only a day or two, so you’ll want to check the plant every day or two during its bloom period and pluck the freshly opened ones.
The same dry-weather rule applies here. Gather flowers when they’re free of moisture, ideally on a sunny afternoon. Drop them into a paper bag or basket rather than a plastic bag, which traps humidity and can start breaking down the delicate petals before you get them home.
Harvesting Roots
Mullein roots are best harvested in late fall of the first year or early spring of the second year, before the flower stalk begins to develop. This timing matters because the plant’s energy is concentrated in the root system during dormancy. Once the stalk starts growing, much of that stored energy gets redirected upward, and the root becomes woody and less useful.
To dig a root, use a garden fork or narrow spade and work around the plant in a circle several inches from the base. Mullein has a taproot that grows straight down, so pulling without loosening the soil first will snap it. Once you’ve loosened the surrounding dirt, grip the base of the rosette and pull steadily. Shake off excess soil and rinse the root with cold water. Slice it lengthwise or into thin rounds before drying, since a whole taproot takes a very long time to dry through and is prone to molding from the inside out.
Drying Mullein Properly
All parts of mullein need to be thoroughly dried before storage. The fuzzy leaves hold moisture surprisingly well, so don’t rush this step.
For air drying, spread leaves in a single layer on a screen or drying rack in a warm room with good airflow. Avoid stacking or overlapping them. Depending on humidity, air drying can take several days to a week. Leaves are done when they feel brittle and crumble easily between your fingers. Flowers dry faster because of their small size, usually within a few days on a screen.
A food dehydrator speeds things up considerably. Leaves take roughly 5 to 8 hours in a dehydrator. Keep the temperature low, around 95 to 105°F, to preserve the plant’s beneficial compounds without cooking them. If you don’t have a dehydrator, you can use an oven set to its lowest temperature. Oven drying typically takes about three hours, but check frequently since ovens vary and the difference between “dry” and “scorched” can happen fast. You’re looking for leaves that snap when bent, not ones that still feel leathery.
Root slices need the longest drying time. Thin rounds on a dehydrator tray or drying screen may take a full day or more. They should be completely hard and dry all the way through, with no flexibility or soft spots remaining.
Storing Dried Mullein
Once everything is fully dried, store leaves, flowers, and roots separately in airtight glass jars. Keep the jars in a cool, dark place, away from direct sunlight. Light and heat are the two biggest enemies of potency and freshness. Properly dried and stored mullein keeps for years.
Vacuum sealing is worth considering if you’re harvesting in bulk. Mason jar vacuum sealers are inexpensive and remove the air that can gradually degrade dried herbs. Whether you vacuum seal or simply use a tight-fitting lid, check your jars after the first few days. If you see any condensation on the inside of the glass, the material wasn’t dry enough. Pull it out and dry it further before resealing, or you’ll end up with mold.
Straining Out the Hairs
This step is easy to overlook but matters if you plan to make tea or any preparation you’ll drink. Those same fine hairs that cover mullein’s leaves and stems can irritate your throat. Whenever you brew mullein tea or make an infusion, pour it through a fine-mesh coffee filter, cheesecloth, or a tightly woven cloth strainer. A standard tea strainer with large holes won’t catch the tiny trichomes. This extra filtration step turns a potentially scratchy cup of tea into a smooth one.