How to Grow, Harvest, and Identify Mullein

Mullein

Sources: NC State Extension, Wisconsin Extension, Hawaii noxious weed rules. Difficulty and pots are our view.

Overview

Mullein grows fast in a sunny, well-drained spot. The catch is time: it takes two years to flower. It grows mostly on disturbed soils in full sun (Wisconsin Extension), and its leaves have a “flannel-like texture” (Ohio State weed guide).

Here’s the short version:

1. Is it easy? NC State rates its growth “Rapid,” and it needs full sun and good drainage. In our view, that makes it easy if you’re patient.
2. Grow it from seed, on the surface. The seed sprouts best in light.
3. A pot or a bed both work, in our view. A pot should be deep.
4. Know it before you pick it. Poisonous foxglove can be confused with mullein when it isn’t in flower. See How to identify mullein.
5. You harvest the big leaves, dry them, and strain the tea through fine cloth.
6. Check safety first. Read the safety notes, and don’t eat the seeds or make anything from them.
7. Not in Hawaii. It’s a listed noxious weed there (see Is mullein invasive?).

Mullein wants 6 hours of direct sun. Our Start Your First Medicinal Herb Garden guide shows you how to watch the light before you plant. That guide also mentions a 4- to 5-hour spot for shadier yards; mullein needs the full 6.

Which mullein to grow

This guide covers common mullein, Verbascum thapsus, also called flannel leaf (Iowa State Extension).

Moth mullein (Verbascum blattaria) is a related biennial that “lacks the densely hairy foliage that characterizes common mullein” (Ohio State). This guide doesn’t cover it, or the other Verbascum species and hybrids nurseries sell.

Buy seed labeled “Verbascum thapsus.” Wisconsin Extension notes that it doesn’t reproduce vegetatively, so grow it from seed.

Where to plant mullein

Give mullein at least 6 hours of direct sun and soil that drains. NC State Extension says it “does not tolerate wet soils” and is “quite drought tolerant.” Its soil list covers clay, high organic matter, loam, sand, and shallow rocky soil. One seed seller says fertilizer is optional and may cost you flowers; the other sources we used don’t mention it.

Spacing: Seeds and Plants thins seedlings to about 18 inches (45 cm), while NC State gives a mature width of 2 to 3 feet. We’d space plants about 2 feet apart.

Is mullein invasive?

It depends on where you live. NC State says it “can grow quickly and densely cover the ground out-competing native species.” It also says its self-seeding “is not considered especially aggressive.”

• Hawaii: it’s on the state noxious weed list. The Maui Invasive Species Committee says “regulations prohibit the intentional propagation and distribution of this plant.” Don’t plant it in Hawaii.
• Colorado: NC State notes it’s listed as noxious there. Check with your county weed program first.
• Wisconsin: Wisconsin Extension says it’s generally not considered an aggressive weed in Wisconsin, because the seed needs open ground.
• Everywhere else: ask your local extension office.

To keep seedlings in check, see Keeping mullein from seeding everywhere.

How to grow mullein from seed

Mullein seed sprouts best in light. Wisconsin Extension says it doesn’t germinate well without light. The USDA Forest Service’s Fire Effects Information System (FEIS) says it germinates best “with exposure to full light and warm temperatures.” Two seed sellers, Sow Right and Restoration Seeds, say light is required.

How much to cover it is where sellers split. Sow Right says to lightly cover it. Seeds and Plants says to “just cover” it with a fine layer. Restoration Seeds says “press into soil, do not cover.” Our advice: press it onto the surface, with a dusting at most.

When to sow mullein: spring or fall?

Sources differ:

• Late spring to early summer: “Surface sow seed in late spring to early summer,” says Wisconsin Extension.
• Spring: Sow Right Seeds says to direct sow after the last frost, or start indoors 4 to 6 weeks before it.
• Fall: Restoration Seeds recommends fall sowing.

In a cold-winter area, we’d sow in spring so the rosette gets a full season before winter. In one Michigan field study in FEIS, none of the seedlings that came up in August, the largest group, survived the winter. FEIS adds that emergence timing “may or may not” affect survival.

Cold stratification? None of the four sources we checked for sowing calls for it, so we’d skip it.

Starting mullein seeds indoors

Hands-on time: about 10 minutes.

1. Fill deep pots or cells with damp seed-starting mix. Seeds and Plants surface sows “into deep pots.”
2. Press the seed onto the surface (see above).
3. Keep it moist and warm. Sow Right gives 65°F and 14 to 20 days. Seeds and Plants gives 59 to 64°F (15 to 18°C) and 2 to 4 weeks.
4. Harden off the seedlings. Plant them out after your last frost, at the spacing above (about 2 feet).

Check: seedlings in about 2 to 3 weeks (Sow Right) or 2 to 4 weeks (Seeds and Plants).

Sowing mullein seeds outdoors

Hands-on time: about 10 minutes.

1. Rake a patch of bare soil in full sun.
2. Scatter the seed and press it onto the surface (see above).
3. Keep the surface moist until seedlings appear. Thin them to the spacing above (about 2 feet).

Check: seedlings are up and thinned.

The two-year cycle: rosette, then flower spike

Year one. Mullein forms “low-growing rosettes of felt-like leaves” (Wisconsin Extension). A rosette can reach 2 feet across (Iowa State Extension). There are no flowers yet. You can pick leaves from the rosette, but sources differ on which year (see When to harvest mullein leaves).

Winter. Wisconsin Extension says cold exposure “is required to induce flowering the following spring.” FEIS notes that southern populations didn’t need that cold period. Plants must also reach a “critical size” before they flower, so some wait past year two (Ohio State).

Year two. Up comes the flower stalk. Heights vary by source: “5 or more feet” (Wisconsin Extension), up to 8 feet (Ohio State), and 3 to 10 feet for the plant overall (NC State). Wisconsin Extension describes small yellow, five-petaled flowers, and Nevada Extension says they bloom from summer to fall.

Then it dies. “After flowering the entire plant dies,” says Wisconsin Extension.

Keeping mullein from seeding everywhere

That flower spike is a seed factory. NC State counts 100,000 to 180,000 seeds per plant, released “mostly very close to the parent plant.” Wisconsin Extension says the tiny seeds stay viable for decades in the soil.

Wear gloves for the steps below: the hairy leaves and stems can cause contact dermatitis (safety notes).

1. Pull unwanted plants early. Wisconsin Extension says to “pull, hoe or dig plants by hand (easiest when the soil is moist)” once they’re big enough to hold, “but before they go to seed.”
2. Don’t rely on mowing. Wisconsin Extension says mowed rosettes “just increase in size and then bolt once mowing is stopped.”
3. Cut the spike if you don’t want seedlings. Cut the flower stalk before the seed capsules ripen (our advice).

For the seeds themselves, see Safety notes.

Growing mullein in pots

No source gives a pot size, so this is our advice. Wisconsin Extension and FEIS call the taproot deep, and FEIS says it forms in the first year. Nevada Extension calls it “bulky but somewhat shallow.”

• Pot: the deepest, widest pot you can manage, with drainage holes. Make it heavy enough that the stalk won’t tip it. The taproot forms in year one, so start the seedling in its final pot rather than repotting later.
• Soil: Our advice: a fast-draining mix, because mullein won’t tolerate wet soil. Our Start Your First Medicinal Herb Garden guide covers containers and drainage, including why to skip the gravel layer. Skip that guide’s compost and fertilizer for mullein, just as it says to for yarrow.
• Water: only when the mix is dry.
• Winter: for the cold mullein needs to flower, see the two-year cycle. Our advice: keep the pot outdoors. In very cold areas, sink the pot into a bed or move it somewhere sheltered but unheated, so it stays cold.
• Indoors? No. It needs 6+ hours of direct sun and grows a tall stalk.

How to identify mullein

Our advice: grow your own from seed labeled Verbascum thapsus. Then check these features:

• Leaves: “Bluish gray-green, oblong to lanceolate leaves are 4-12″ long and 1-5″ wide, and are densely covered in hairs” (Wisconsin Extension). Hairs on both sides give “a frosted appearance and a flannel-like texture” (Ohio State).
• Stem (year two): Ohio State says the stem is “erect, rigid,” and “covered with wooly, branched hairs.” It adds that “stems appear winged due to leaf bases that extend longitudinally down the stem.”
• Rosette and flowers: see the table below.

Mullein vs foxglove

Sources: Wisconsin Extension and Ohio State for mullein; Woodland Trust for leaf edges and hairs; NC State Extension for foxglove.

Both rosettes are hairy, so “fuzzy” alone proves nothing. Britain’s Woodland Trust names mullein as a plant foxglove “might be confused with when no flowers are present.” Use this table as a second check on a plant you sowed, never as permission to forage.

Harvesting, drying and straining mullein

When to harvest mullein leaves

Sources differ. Seeds and Plants says “Mullein leaves are gathered in the first year of growth.” An Ask Extension expert says “the best time to harvest mullein (a biennial) is during its second year of growth when it is mature and flowering,” cutting large leaves from the base.

That expert picks leaves while the plant is flowering. None of the sources covers picking after the flowers finish.

How to harvest mullein leaves

Hands-on time: about 5 minutes.

1. Make sure it’s mullein, not foxglove (see How to identify mullein above).
2. Put on gloves: the hairy leaves and stems can cause contact dermatitis (safety notes).
3. Cut large, healthy leaves at the base with kitchen shears ad . Leave some on the plant, as the Ask Extension expert advises. We’d leave the center of the rosette alone too.
4. Shake off soil. Rinse only dirty leaves, then pat them dry.

Check: the rosette still has its center and several leaves.

How to dry mullein leaves

Hands-on time: about 10 minutes.

1. Keep your gloves on, because the leaf hairs can cause contact dermatitis (safety notes). Spread the leaves in a single layer somewhere airy, out of direct sun (Ask Extension). A wire cooling rack ad lets air reach both sides. Or use the oven or dehydrator settings in our guide to drying herbs.
2. Ask Extension suggests about a week, or until the leaves are completely dry and crumbly. These thick leaves may take longer than the drying guide’s times for leafy herbs.
3. Store the crumbled leaves in a labeled glass jar with a tight lid ad in a dark cupboard.

Check: the leaves crumble, with no soft spots.

How to strain mullein tea

A review in Evidence-Based Complementary and Alternative Medicine notes that most traditional recipes for a leaf decoction (tea made by boiling the leaf) strain out the leaf hairs before the tea is drunk. Restoration Seeds agrees: “Carefully strain leaves to remove the small hairs.”

Our advice: make the tea as in our hot infusion guide. Then line a fine-mesh strainer ad with cheesecloth folded double, or use a coffee filter, and pour without pressing. That guide says to press the herbs; skip that step for mullein.

Before you drink it, ask your doctor or midwife if you’re pregnant or breastfeeding, your pediatrician before giving it to a child, and your doctor or pharmacist if you take any medicine (safety notes).

Check: hold the cup up to the light. You shouldn’t see any floating fuzz.

Traditional uses

The European Medicines Agency’s assessment notes that “both leaves and flowers of mullein have been used in folk medicine.” The same report says the stems were once dipped in suet or wax to make torches. Wisconsin Extension adds that the flowers were used to make yellow, green, or brown dyes.

An EU herbal monograph accepts mullein flower tea as a traditional herbal medicine for ages 12 and up. That status rests on long-standing use, not clinical trials. It covers licensed flower products, not the leaf, and this guide doesn’t go into its listed use.

Parts used

This guide covers the leaves. For the European flower listing, see Traditional uses. For the seeds, see Safety notes. The roots are outside this guide.

Common preparations

Read the safety notes below before you drink any mullein preparation. None of the references in our safety notes covers the leaf in pregnancy or breastfeeding, so ask your doctor or midwife first. Ask your pediatrician before giving it to a child, and your doctor or pharmacist if you take any medicine (safety notes).

• Tea/infusion: dried leaf in hot water, strained through fine cloth. See our guide to hot infusions and How to strain mullein tea. Check the cautions above before you drink it (safety notes).
• Infused oil: use dried leaves only; our guide to infused oils explains why. Strain through fine cloth without squeezing, to catch the hairs. The oil guide says to squeeze; skip that for mullein. For external use only. Wear gloves while you handle the leaves, since the hairs can cause contact dermatitis (safety notes).
• Drying for storage: see our guide to drying herbs. Handle the leaves with gloves on (safety notes).

Companion and garden notes

Mullein likes what yarrow likes: full sun and soil that drains fast. They can share a sunny, dry corner. Plant mullein at the back of the bed, so its stalk doesn’t shade shorter herbs.

Livestock typically avoid common mullein, according to FEIS.

Safety notes

These notes are about drinking or eating mullein, not growing it. NCCIH’s Herbs at a Glance and Memorial Sloan Kettering’s About Herbs database have no mullein entry. The European Medicines Agency’s only mullein monograph covers the flower, not the leaf.

What the flower monograph says: these cautions cover licensed mullein flower tea products. The EU monograph says “the use during pregnancy and lactation is not recommended,” because safety “has not been established.” It also says “the use in children under 12 years of age is not recommended.” Don’t use it if you’re allergic to it.

The monograph lists interactions as “None reported” and side effects as “None known,” but that isn’t proof there are none. It also says: “Adequate tests on reproductive toxicity, genotoxicity and carcinogenicity have not been performed.”

Pregnant or breastfeeding: none of these references covers the leaf. Ask your doctor or midwife before you drink it.

Children: ask your pediatrician first.

Medicines: NCCIH says you “should talk with your health care providers about all dietary supplements and medications you take.” So ask your doctor or pharmacist before drinking mullein if you take any medicine.

Skin: “The hairy leaves and stems can cause contact dermatitis,” says the Ohio State weed guide. Wear gloves when you harvest and handle the leaves.

Seeds, and leaves eaten in quantity: Ohio State’s weed guide says common mullein “foliage and seeds contain a mild narcotic and may induce sleep if eaten in large quantities.” FEIS says early settlers “used common mullein seed to sting or poison fish,” and it describes the seeds as toxic to fish. Don’t eat the seeds or make anything from them.

Foxglove: if you aren’t certain a plant is mullein, don’t use it. NC State rates foxglove’s poison severity “High.”

Pets: no ASPCA listing for mullein turned up. If you have pets that chew plants, ask your vet.

Mullein asks for sun, drainage, and patience. Sow a little seed each spring, and you’ll have rosettes and flower spikes coming along in turn.

Planning the rest of your patio? Start your first medicinal herb garden walks you through pots, drainage, and light.

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