Pound for pound, you get more out of mulleins (Verbascum species) than almost any other flowering garden plant. They were favourites of Henry Mitchell, who appreciated big plants. He wrote in praise of V. bombyciferum, which he called the “bomb-carrying mullein,” a type with leaves so fuzzy they are almost white.
The mullein I know best is V. olympicum, the Olympic mullein. It is well-named, being of Olympian proportions. I have had plants ten feet tall, although eight is more common. It grows splendidly in my sandy soil with little supplemental water, and is not troubled by the shade and maple tree roots that have rendered my back garden inhospitable to fussier plants.
The Olympic mullein, like many of its clan, is a biennial. In its first year it grows an impressive rosette of grey-green leaves up to 2 feet long and a formidable taproot. In its second year, it sends up a bloom stalk that develops through the spring and early summer, topping out between six and twelve feet.
In July, the plant begins to bloom, looking positively torch-like and attracting hordes of bees. There are zillions of buds, so the overall flowering effect lasts for weeks, but sometime in August things start to look a little sparse and spotty. At that point the thing to do is to take shears in hand and decapitate the plant, cutting just below the flowering side-stems.
A few weeks later, new flowering stems start to grow in the spots where the leaves join the main stalk, and soon there is a new flush of bloom that lasts well into the fall. That’s the stage my plants are in now, and given the generally dilapidated state of the garden, this fresh and vigorous mass of bloom is very welcome. The bees think so too, and are back in such numbers that when you stand near a mullein,it sounds like the whole thing is buzzing.
I grew my first mulleins nearly 20 years ago, from purchased seeds. I let the first couple of plants I grew go to seed, ensuring that I would have them always, even though individual plants generally die the winter after they bloom. I recommend allowing a certain amount of seeding, but not letting plants have their way, in which case they truly are bomb-like, producing explosions of seedlings. A mullein forest would be rather surreal. It’s best to cut the plants down in late fall, once the second flush of bloom becomes sparse. And by “cut” I mean “saw,” because the stalks are 2 or 3 inches in diameter at the base and quite woody. They leave stumps which are best dug up the following year, when the roots have decayed somewhat.
Mulleins can be transplanted when they are young, up to about 8 inches tall and wide, before their taproots become too established. I select a few every fall or spring and position them where they will be assets rather than obstacles. Then I rigorously remove the rest of the volunteers, although I hate to dispose of such healthy and vigorous plants. But I don’t have room for a mullein forest.