Flower stalks grow quite tall (anywhere from two to seven feet), bearing small, yellow (rarely white), five-petaled flowers grouped closely on a leafy spike. Blooming a few at a time from June to September, they mature from the bottom to the top of the spike in spirals. In addition to its especially soft, felt-like foliage, another characteristic that makes this plant unique is that each individual bloom opens before sunrise and closes by mid-afternoon. Flowers attract flies, butterflies, short- and long-tongued bees, and other insects.
Light
Mullein thrives in full sun. Plant them in a dry, warm spot near walls or large trees to protect them from wind.
Soil
Grow mullein in just about any type of soil, preferably soil that is dry and slightly alkaline. The plant will also adapt to poor, calcareous soil. Being so adaptable, it can spread quickly, creating dense patches even faster than some native plants.
Water
Keep the soil moist when growing mullein from seed. While the plant doesn’t need much moisture, water more often as it starts to flower.
Fertilizer
Mullein can grow faster and produce more flowers when fed with a low release 10-10-10 fertilizer.
Types of Mullein
More than 300 varieties are native to Europe, West and Central Asia, and North Africa. Of the Scrophulariaceae snapdragon family, their long terminal flower spikes are reminiscent of snapdragon flowers. Common types spread quickly and can be controlled in their first year by weeding out young rosettes, but hybrid types (called ornamental mullein) tend to be less invasive and better for gardens. Flowers come in white, pink, lavender, purple, and yellow. Here are a few types of mullein to consider:
Moth mullein (V. blattaria), which has white or yellow flowersOlympic (or Greek) mullein (V. olympicum), which has five-foot branching stalks of bright yellow flowersPurple mullein (V. phoeniceum), a short-lived variety that reaches a compact three feet tall and produces dark purple or violet flowersNettle-leaf mullein (V. chaixii), a compact variety that grows two to three feet tall; it has white blooms with purple centers that are long lasting
Propagating
Propagate mullein from seeds and cuttings. Either buy seeds or collect seeds from plants as soon as the fruits are borne from flowers.
How to Grow Mullein From Seed
The fruit of a mullein plant is a round capsule, which splits into two. Each fruit has dozens of very small brown seeds. Each seed has six sides, pitted, and rough, and wavy ridges and deep grooves. Every plant can make between 200 and 300 seed capsules, each having between 500 and 800 seeds, which equals a whopping 100,000‑240,000 seeds per plant. Seeds usually fall just a few feet away from the parent plant, blown down by the wind or shaken down by an animal animal. None are known to disperse long-distance. Seeds can remain alive and viable for decades in the soil. Seeds that are on the surface or just below it will have enough light to germinate. So the more the soil is disturbed, the more likely seeds will emerge and sprout. That’s why these plants are so invasive in areas with poor to average soil disturbed by logging, fire, and storms. Drought-tolerant and prolific seed producers, the plant grows quite easily from seed. Start seeds indoors in early spring or outdoors in late spring. Scatter them on the top of rich potting soil or sow a pinch of seeds 18 inches apart and just 1/16 inch deep in well-drained soil. Look for sprouts two weeks later. Once they have grown a true set of leaves, divide and transplant the seedlings into a bigger container or harden them off and transplant them into the garden. Because these plants readily self-sow, remove unwanted plants to keep your garden from being overrun with mullein.
Overwintering
Also frost-resistant, mullein tolerates temperatures as cold as 5 degrees Fahrenheit. For extra root protection, mulch before the projected frost date with twigs, leaves, and bark.
Common Pests and Plant Diseases
Mullein is resistant to pests. Aphids are only rarely a problem. Avoid planting mullein in heavily compacted soil as such poorly draining soil can encourage root rot.
