Ohio Landscape Association

Perennial Focus

Aconitum Monkshood

As temperatures drop and days grow shorter, fall-blooming perennials become more treasured for they reassure us that winter is not yet here. We still have blue skies and most species of the genus Aconitum are merely a deeper reflection of those skies.

Aconitum are beloved by those who live in deer country because the roots, leaves and stems of the plant are poisonous. This is not to say that we want to poison the deer - that would not be nice - we merely want to discourage them.

Most fall-blooming perennials are tall and Aconitum are no exception. They tend to be anywhere from three to five feet high depending on species and cultivar. The stately spires of flowers bloom above foliage that is alternate and palmately divided. Aconitum do best in full sun and adequate moisture. They will grow in partial shade but seem more prone to fungal diseases there which blacken the foliage.

The best species for fall bloom is Aconitum carmichaelii, the Azure Monkshood. This sturdy perennial rarely needs staking and has dark blue flowers in the fall. Allan Armitage, the perennial guru, says that Arendsii' is the best cultivar and also the latest bloomer during the months of September and October. Mine does not usually bloom until October. Another excellent cultivar is Barker's Variety' that has flowers of a deeper blue. Both grow four to five feet tall.

Another late blooming and hard to find species is Aconitum lamarckii. Its flowers are creamy white to pale yellow, rather than blue, and its stems are quite lanky, so I wind them through my Phlox paniculata and the Ilex crenata behind it.

If you like the look of Aconitum, you could also try the summer species of this perennial. Aconitum napellus (Common Monkshood) usually starts blooming in June. This three to four foot high species is the easiest to find. In addition to the blue hue of the species, the colors white and pink can be found in the cultivars Album' and Carneum' (Roseum'), although the pink becomes white, unless night temperatures are cool.

Aconitum x cammarum (Bicolor Monkshood) will bloom variably from July to August depending on the cultivar, generally growing three to four feet tall. The spires are often branched and somewhat arched. Bicolor' is probably the best known cultivar and has blue and white flowers loosely born on wide branching panicles. 'Bressingham Spire' is a bit shorter with violet blue flowers in dense, upright panicles.

Fall blooming Aconitum look wonderful with other perennials such as Eupatorium purpureum (Joe Pye Weed), Boltonia asteroides Snowbank' and Sedum Matrona'. The Joe Pye is taller and has a bolder texture. The Boltonia is approximately the same height but has a much finer texture and the Sedum, with its bold and leathery foliage, is an excellent foreground perennial.

I recommend all of the Aconitum to you. If you use all of the species, one of them will be blooming from June to October.

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