The plant genus Verbascum, commonly known as Mullein, is a striking addition to many gardens. Recognized for their imposing, vertical spires of blossoms, these plants bring dramatic height and structure to the landscape. The genus contains approximately 300 species, displaying a wide range of sizes and flower colors. The exact lifespan of a Verbascum plant depends entirely on the specific species or hybrid being grown, which is the source of frequent confusion for those looking to cultivate it.
Life Cycle Clarity: The Annual, Biennial, and Perennial Distinction
The question of whether Verbascum is a perennial or a biennial has a nuanced answer, as the genus includes species that fall into all three life cycle categories. The most common wild type, Verbascum thapsus (Common Mullein), is a classic biennial plant. A biennial requires two full growing seasons to complete reproduction before dying. In the first year, it forms a low-growing, dense rosette of leaves that survives the winter. In the second year, the plant bolts, sends up its characteristic tall flower spike, sets seed, and then perishes.
The perception that all Verbascum are perennials often stems from their highly successful self-seeding habits. Prolific self-sowing creates a continuous succession of new plants each year, giving the appearance of a permanent, perennial stand. True perennial species, such as Verbascum nigrum and Verbascum phoeniceum, are shorter-lived, generally lasting only a few years. They return from the root crown annually rather than dying after flowering.
Key Characteristics and Appearance
The physical structure of Verbascum provides a strong vertical element in garden design, with mature plants often reaching heights between two and six feet. The signature feature is the rigid, unbranched flower spike, which is densely packed with numerous small blossoms. Individual flowers are typically five-petaled and saucer-shaped, with colors ranging from the familiar bright yellow to white, pink, and deep purple depending on the variety.
The foliage also offers a distinctive texture, particularly in biennial types like V. thapsus. These develop large, oblong basal leaves coated in fine, woolly hairs, giving them a soft, silvery-gray or felted appearance. This dense pubescence helps the plant manage water loss in dry environments. In contrast, perennial species like V. phoeniceum have basal leaves that are less hairy and often smoother and darker green.
Essential Growing Conditions
Verbascum plants are highly adapted to challenging environments, preferring sites that replicate their native Mediterranean and Central European habitats. They require a location that receives full sun for a minimum of six hours daily to achieve their best growth and flowering potential. Excellent drainage is the most important soil requirement, as the plants are intolerant of wet conditions, especially during the winter months.
They thrive in poor, sandy, or rocky soil and do not require high levels of fertility. Overly rich soil can cause the tall stems to become weak and potentially require staking. Once established, Verbascum exhibits significant drought tolerance due to its deep taproot system. Gardeners can encourage a second, smaller flush of blooms by cutting back the spent main flower spike (deadheading).
Popular Garden Varieties
Gardeners seeking a reliably returning plant should focus on perennial or short-lived perennial hybrids. Verbascum phoeniceum (Purple Mullein) is a naturally occurring perennial species that is shorter and often has violet or purple flowers. This species is a parent to many contemporary hybrids that offer a wider color palette and a longer lifespan.
The ‘Cotswold Group’ is a well-regarded collection of hybrids, including varieties like ‘Cotswold Beauty’ and ‘Cotswold Queen’, known for their buff, apricot, and peach tones. Another excellent perennial choice is ‘Southern Charm’, which produces spikes of apricot-pink flowers with contrasting purple-pink centers. These cultivated varieties provide a more predictable and colorful display compared to the wild biennial species.