Colorful monkshoods make killer perennials

Monkshood, wolfsbane, blue rocket, friar’s cap — the lovely purple flowers of the Aconitum are often mistaken for delphiniums. Like their cousins in the Ranunculaceae, they are beautiful, long-lived mid-to-late summer bloomers. However, they are like their cousins — quite toxic.

The alkaloids in these plants were historically used as a poison to kill wolves, tigers or one’s enemies. Mystery readers will remember the liniment that medieval monk Brother Cadfael made from a mix of the ground root of monkshood mixed with mustard oil and flax seed that was eventually used to “off” the victim in Ellis Peter’s book “Monk’s Hood.”

A relatively large genus, Aconitum (ack-on-eye-tum) has some 60 species, half of which are considered medicinal. Its natural habitat is in mountainous regions from Scandinavia through Siberia and into the Himalayas. And while its deadly character gives it place in many a myth and history, it is also a beautiful and stately perennial found in many northern gardens. Unless you have children or animals that tend to chew the plants in your garden, or are planning the demise of an unruly neighbor, you have little to worry about and can delight in their vertical addition to your garden. After all, there are a great many common garden plants that will poison your afternoon. Take them all out of the garden and there will be few plants of color left to enjoy.

Aconitum are perfectly suited for northern climate gardens as they enjoy cool summer nights, moist rich soils and can take some shade as well. Most of us know the wild woodland variety, Aconitum delphinifolium, with its royal purple helmet-shaped flowers dotting the under story in the local forests. While these can be transplanted into a garden, it is their domesticated cousins that are the real showstoppers. A few varieties are less than 3 feet tall, like Aconitum septrionale “Ivorine,” but most are robust growers in the 4-to-5-foot tall range. And it may surprise you to know there are more colors to look for.

Ivorine is, like its name, an ivory flowered 2-to-3-feet tall variety with narrow long helmets that bloom early for a monkshood. On the hillside they bloom around June. A Swedish introduction, this plant is extremely tough and may self-sow, which is very unusual for Aconitum as they are quite a challenge to start from seed. Ivorine looks wonderful paired with any burgundy leaved Berberis or a rich blue Hostas.

A. lamarickii, “wolfsbane,” a yellow variety with a similarly narrow shaped blossom can reach upwards of 5 feet in height. It tends to be less compact a grower than most and looks well loosely threading through delphiniums and thalictrum. I have yet to lose a monkshood to winter until this year when my large specimen of A. lamarickii died. Fortunately, I have a few smaller ones tucked away in the propagation beds, so all is not lost.

A. Carneum and A.napellus Roseum or Rubellum are pink varieties with large, fat blossoms on tall stems. While Roseum is supposed to be a deeper pink, both varieties are a fleshy shell-pink in my garden. Carneum means “flesh-colored,” and so it is. These two varieties pair well with blue and purple delphiniums, chimney bells, Thalictrum, and the tall Campanula latifolia.

Aconitum x cammarum Bicolor is a tall variety with fat white helmets edged in royal purple. Eleanor is white with just a touch of navy blue on her lips. Their cousin, Stainless Steel, has plump pewter silvery blue helms. They all pair well and contrast nicely with hardy roses like the blushed semi-double Helen Bland or a deep magenta variety.

A. napellus Newry Blue is a tall deep purple blue monkshood with a looser conformation and looks nice with burgundy or yellow leaved Berberis, Diabolo Ninebark, the rich gold and red-tipped Spirea Gold Flame, and the stately plum flushed Thalictrum rochebrunianum.

Aconitum are vigorous plants which tend to need spring dividing in a few years’ time. The green nubs of tiny helmets peeking out of the ground are one of the first signs of spring. This is the best time to divide and add compost as, like their delphinium cousins, they are heavy feeders. If you ignore them they’ll still put on a show. But, treat them with respect and you’ll enjoy them for years to come. And if you’re worried about poisoning the neighbors you can substitute lily of the valley and daffodils in the stir fry. That’ll do them in even quicker!

For thoroughly toxic romp visit the Duchess of Northumberland’s Poison Garden at Alnwickgarden.com.

Brooke Heppinstall, artist and gardener, is the owner of Wool Wood Studio & Gardens, an art studio and nursery specializing in Alaska-grown perennials and shrubs. Visit online at Woolwood.blogspot.com.