biennials

My Tough Plants #3: Olympic Mullein

The first two plants in this series could be described as medium-sized. They don’t look like much from a distance. The Olympic Mullein is different. It’s big and striking. It’s architectural. I’ve seen mulleins more than 10 feet tall. Even so, it’s relatively skinny for its height, making it a perfect “statement” plant in a bed of shorter subjects, a visual exclamation point.

Mullein rosette from above

Most mulleins, including the Olympic one, are biennials. They spend their first year as a “rosette” of large fuzzy leaves radiating from a centre point at ground level. This rosette can take up a fair bit of space — up to 3 feet in diameter. The big leaves can overwhelm any small, delicate plants nearby, so keep that in mind when siting mulleins.

Olympic mulleins, Verbascum olympicum

In the second spring, drama begins. A single bloom stalk emerges from the middle of the rosette and rises skyward. You can see it lengthen from one day to the next, shooting out lush leaves topped by a vaguely phallic structure consisting of the immature flower stalks. By the time this unfolds into a glorious mass of yellow, the plant attains its full height, anywhere from six to ten feet. Bees love the flowers. A plant in full bloom on a hot July day buzzes with their activity.

I must have grown my first Olympic mulleins here from seed, back in the early 1990s. Since then, I haven’t needed to buy more seed or new plants. At some point, I acquired a plant of white mullein (Verbascum chaixii ‘Album’). It’s smaller and daintier (if you can call any mullein dainty). It has a single spike of flowers, rather than the broom-like structure of the Olympic mullein. The flowers, of course, are white and the stamens are purple, unlike the Olympic mullein, whose flowers are entirely yellow. After a couple of years I began noticing smaller plants with single bloom spikes and yellow flowers with purple stamens. The two types must have gotten together and hybridized. Plants do stuff like that. Unlike their Olympic cousins, the white mullein and the yellow + purple hybrids are perennials.

White mullein, Verbascum chaixii "Album" with bee

White Mullein with Bee

Another noteworthy mullein I’ve seen in other gardens is Verbascum bombyciferum, silver mullein. It’s not quite as big as Olympic mullein, and its leaves are heavily felted with white fuzz, a distinctly attractive feature. I’ve never managed to find a spot for it here, but I mention it because it was a favourite of that estimable gardener and garden writer, the late Henry Mitchell. He claimed the Latin name meant “carrying a bomb,” something I’ve never felt the need to verify.

Mulleins are trouble-free plants, drought-tolerant, deer-resistant, utterly reliable, at least in my garden with its sandy soil and dry summers. Even the maple roots and shade don’t faze them, although they do best in the sunniest spots in the garden. They don’t need staking.

Olympic mullein, Verbascum olympicum, second bloom

Dependable mullein with second flush of bloom

Like many other tough plants, mulleins are prolific seed producers. Before I figured out a management method, a lot of seeds were deposited in my garden. That seed bank, probably supplemented to some extent by the odd stalk that escapes deadheading, has kept me in mulleins for a quarter century. They seem to form new buds even as the first lot of flowers fades, so I’m often surprised to see fresh flowers on a plant I thought was finished blooming. I suspect this is a way to fool the gardener into delaying deadheading and giving the plant time to ripen seeds from the earliest blooms. Anyway, once they truly are finished blooming, all you have to do is decapitate them. Cut the main stem just below the cluster of bloom stalks. Snip — done. It’s probably best to dispose of the spent stalks somewhere other than the compost pile, unless you don’t mind mullein seedlings popping up from the compost. Young plants are easily transplanted while small enough to dig up with taproots intact. Move them in spring and revel in their gorgeousness the following summer.

Maple Leaf and Mullein

The decapitated plants cheerfully put out a fresh crop of bloom stalks, smaller and shorter than the original ones, and eventually a new batch of flowers for late summer and autumn. I’ve had mulleins in bloom as late as November. Eventually, though, it’s all over. Like all biennials, Olympic mullein plants die at the end of the second year. Once the leaves are dead and the plants look ugly, I cut the stalks at the base, using a small saw, because they are quite thick and woody. But I know there are half a dozen young plants waiting to do their thing the following year, and mullein seeds lurking in the soil.

Mullein (Verbascum olympicum)

Foxglove Falsehood

I know I read somewhere that the flower colour of a foxglove (Digitalis purpurea) plant can be predicted by the colour of the leaf stems (petioles). Foxgloves are biennials; they flower in their second year of life, and then they die. Their normal flower colour is a reddish purple. It’s fairly attractive, but not nearly as elegant as the white form. Fussy gardeners who prefer the white form would therefore want to know which of a batch of seedlings would be likely to produce white flowers the following year.

If the leaf stem shows purple, I understood, the flowers will be purple. Plants with pale green leaf stems are more likely to produce white flowers. Going by this, I picked out a number of seedlings several years ago and planted them around the place. A few of them did turn out to have white flowers, but not all. Some produced blooms of a pale, washed-out pink with nothing to recommend it, and some were just the ordinary purple shade.

After this experience, I didn’t bother with systematic seedling selection. I simply let a few plants produce seed, and left a few of the resulting seedlings where they came up, in spots where a foxglove would be an asset to the scene.

Right now, I have two foxgloves with white flowers. The biggest and most impressive one has dark purple leaf stems. So does the smaller one.

Clearly, the idea that leaf stem colour predicts flower colour is dead wrong.

Just for fun, I checked the leaf stems of a rather impressive purple foxglove also in bloom now.

Its leaf stems have only a slight tinge of purple. If I had looked at them before the plant bloomed, I would very likely have predicted pale or maybe even white flowers.

So much for that notion. Consulting that fount of info, Wikipedia, I find this in the article on Digitalis purpurea:

The colours of the petals of the Digitalis purpurea are known to be determined by at least three genes that interact with each other.^[6]

The M gene determined the production of a purple pigment, a type of antocianin. The m gene does not produce this pigment. The D gene is an enhances of the M gene, and leads it to produce a big amount of the pigment. The d gene does not enhance the M gene, and only a small amount of pigment is produced. Lastly, the W gene makes the pigment be deposited only in some spots, while the w gene allows the pigment to be spread all over the flower.

This combination leads to four phenotypes:

M/_; W/_; _/_ = a white flower with purple spots;
m/m; _/_; _/_ = an albino flower with yellow spots;
M/_; w/w; d/d = a light purple flower;
M/_; w/w; D/_ = a dark purple flower.

If I could understand the above and make practical use of it, I might be able to predict flower colour in foxglove seedlings. I’d probably get more white flowered plants from my self-sown foxgloves if I pulled up any purple types before they reached full bloom, so as to keep their pollen out of circulation. But I am constitutionally incapable of pulling up (i.e., killing) any plant that is vigorously growing and about to bloom. I even have trouble dispatching certain weeds. So I’m not likely to go around “roguing out” any purple flowered plants if they look good.

In the meantime, I’ll enjoy the blooms I have, and let the white one (which, according to the above, is the white with purple spots phenotype) produce seed. Foxgloves seed like crazy. I’ll harvest a small quantity of seed and sprinkle it around the garden, and in 2019 I’ll see the results.

Update: another, rather small, foxglove plant has since bloomed with white flowers. These are pure white, and without spots of any kind. And the leaf stems are very pale green, without a trace of purple. So now I’m wondering if the leaf stem colour is somehow linked to the colour of the spots within the flower. Observing stuff like this makes gardening — even with common plants — interesting.

Magnificent Mulleins

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.