This is a remarkably large genus, with somewhere between 250-300 species found throughout cold parts of the northern hemisphere, often at high elevations. They have been known for centuries as aconite and wolfsbane. They have been mentioned by Shakespeare, JK Rowling, and were believed by the ancient Greeks to have sprung up from the slobber of Cerberus, the three headed dog that guarded the gates of Hell. They called it “queen of poisons”.
All of the monkshoods are herbaceous perennials, and they can live from 10-20 years or sometimes even longer. They have palmate or palmately lobed leaves and as a result of their acute toxicity, they have practically no pest or disease problems. Monkshood is toxic and contains up to 11 known alkaloids in monkshood, most notably aconitine. Gardeners should be advised to wear gloves when handling monkshood. This is not a plant to treat carelessly. That said, they are also very much worth adding to your garden.
Monkshood has been cultivated for millennia, both as a poison and medicine (in very minute amounts), but also for its beauty. The dusky colored flowers are quite showy and make great cut flowers, and they are also attractive to bees, butterflies, and hummingbirds. The nectar, remarkably, is non-toxic.
Monkshood is easy to grow, very hardy, and quite adaptable. Compost enriched, well drained soil with good moisture conditions suit them best, but they are extremely tough and can make do with much less. A sunny position with a bit of shade from the hottest part of the afternoon sun is ideal. Do not plant them in too shady a location or they will flower poorly and be more prone to powdery mildew.
They are difficult propagate from seed but established clumps are fairly easy to divide in spring or fall. This should only be done once every four or five years. They self sow occasionally. To avoid this, deadhead after flowering. Seed production dramatically reduces their vigor.
Types of monkshood
Aconitum carmichaelii (A. fischeri) is native to Russia, China, and Japan. It grows about 3-4 ft. tall and blooms late summer and often into fall. The flowers are a deep violet-blue to blue-purple and very showy. It is resentful of dry soil and competition, but other than that, it is hardy and worth growing. ‘Arendsii’ is a particularly compact, heavily blooming selection that has received the RHS award of merit. Historically, this species was used as an arrow poison.
Aconitum hemsleyanum- Although most monkshoods grow in a tidy clump, a select few of them actually grow as slender, twining climbers. This is one such species, hailing from central and western China. It is quite easy to grow, and will climb 8-10 ft. in a single season. The flowers are a lovely blue and appear from mid summer through fall. It is resentful of dry soil, but otherwise trouble free. Officially it is hardy to about zone 4, but it has done well in both zones 2 and 3. ‘Red Wine’ is a cultivar that is believed to originate from this species. In 1989, the Gothenberg Botanic Garden in Sweden received seeds from China for what was supposed to be A. hemsleyanum. One of the seedlings had gorgeous, wine red-burgundy blooms that were quite different than what was expected. At first it was thought to be an unknown species; later the experts suggested that it was in fact one of those rare, naturally occurring hybrids that actually comes true from seed. As of 2006, it has received limited attention in the nursery trade but it’s a gorgeous thing and potentially worth acquiring, although early reports suggest it is not as hardy or as vigorous as its parent.
Aconitum napellus- From central and western Europe, this is a very commonly cultivated species. It grows 3-4 ft. tall, flowers in mid to late summer, and has more finely divided leaves than many species. Blossoms range from blue through purple, but variations with pink or white blooms are not rare. This species has been much used in hybridization. ‘Albidus’ is a particularly stunning white flowered form that we recommend.
Aconitum lamarckii (syn. A. pyrenaicum)- A very hardy European species with rather lovely, pale yellow to ivory colored flowers. It isn’t cultivated very often. ‘Ivorine’ is an especially vigorous, heavy blooming cultivar. It looks great when grown in mass.
Aconitum x ‘Blue Lagoon’- Perhaps shortest, most compact of the monkshood. It grows only 12-14” tall and produces bright blue flowers over a long period.
Aconitum x ‘Bressingham Spire’- A vigorous, compact grower to 3 ft. It is a profuse bloomer with large, showy blooms that are as close to true blue as found in monkshood. RHS award of merit.
Aconitum x cammarum- A well known hybrid of A. napellus, these are vigorous growers that flower profusely. The best known is probably ‘Bicolor’, with a spectacular display of gorgeous royal blue and white flowers over a long period. It has received the RHS award of merit. ‘Pink Sensation’ is one of the better pink monkshoods, with softly rose colored blooms and a vigorous growth habit. ‘Stainless Steel’ is a favorite, with long wands of pale, steely blue blooms over a long period. It is a robust grower and flowers abundantly.
Aconitum x ‘Spark’- There is a great deal of misinformation surrounding this particular variety. It is believed to be a hybrid between A. henryi and A. x cammarum ‘Bicolor’ going back several generations. It is most often sold as Aconitum ‘Henry Spark’ or as ‘Spark’s Variety’. Regardless of its origins, this summer blooming monkshood has loosely clustered, very pretty purple-blue flowers and blooms over a long period. 3 ft. is about average, but it can sometimes grow as tall as 7 ft. and be very floppy. We suggest either staking it or growing it near a shrub that it can drape itself over.