The first aconitum to flower for me is Aconitum 'Ivorine ', appearing in May or June. It has apple green leaves with 75 cm branching stems set with ivory-white hooded flowers. I used this plant for Chelsea 2009, partnering it with blue aquilegia among many other plants (see Autumn 2009 Ranunculaceae Group Newsletter). It likes cool conditions and will grow well in semi-shade but not too dry. Very prolific in seed and this is easy to collect at the end of July. Sow the seeds straight away in pots and put them in a cold greenhouse or coldframe for the winter. Seedlings will appear in February or March.
Aconitum anglicum also flowers in May and June but is a little taller at 85 cm, with dark green fine cut leaves and dark blue hooded flowers. This is a native woodland species so will grow well in shade but in my experience does not like it too dry.
Aconitum lycoctonum subsp. vulparia is a little different having large pale-green leaves with long branching stems carrying green-tipped yellow flowers for a long time. My plant starts flowering in early June and continues through to August. I grow it with several different ferns and its flowering stems weave themselves through the fronds. This one is very easy to propagate from seed.
At the end of June, Aconitum 'Stainless Steel' comes into flower with pale steely-blue flowers and both the fine-cut leaves and the stems have a grey flush to them. This is a delightful plant, holding itself well and growing to a height of 80 – 90 cm. This plant grows in full sun under the spreading branches of my neighbour’s oak tree.
Flowering in July, Aconitum napellus 'Bergfürst' and A. n. 'Blue Valley' are both good, stately plants for the back of the border, growing to just over a metre with light indigo-blue flowers and dark green foliage, but needing no staking. I think A. n. 'Bergfürst' has more foliage per stem.
A lovely aconitum that I was given which also flowers in late August – September is Aconitum japonicum. It grows to about 120 cm with good, strong stems with dark, divided leaves and has very good subsidiary flower heads as well as the terminal ones. They are a lovely luminous lavender-blue and they flower for a long period.
I also have Aconitum japonicum subsp. napiforme B&SWJ943 which I bought from Crûg Farm in 2007. This is a shorter plant, some 70 cm tall, and has the same dark, divided leaves but the flowers are a much darker blue. It doesn’t flower until well into September.
There are two late-flowering aconitums that I bought from Tom Mitchell which I would recommend, Aconitum chiisanense is very tall and I grow it against my 2 metre high rear fence and it just reaches the top. It has lovely cut leaves which start off quite a pale green getting darker as the season progresses. By early September they then start to take on autumn tints of red, orange and yellow just as the flowers start to open a good purple blue colour – a lovely sight.
Aconitum uchiyamae is very similar but not so tall, growing to about 95 cm and I think that its flowers, which appear at the end of August, are a little darker.
The last to flower are the Aconitum carmichaelii plants of which I have four different named varieties. The tallest, A. c. 'Cloudy', is about 80 cm and has good dark foliage and the flowers are white, flushed quite heavily with violet. This one usually flowers well into October.
A little shorter at 65 cm is A. c. ex Nepal ex Kath Dryden. This is a really good plant keeping its dark green leaves well and has a mixture of pale to mid-blue flowers. This one is not in the RHS Plantfinder but is in Bob Brown’s catalogue.
Two that I bought from Bob Brown have interesting early foliage. First was A. c. 'Royal Flush' with deep red leaves in spring as they emerge from the soil. As they grow they become green and get to 60 cm with flowers that are a really good clear deep blue. I like to grow this with Aster 'Little Carlow' – they look lovely together.
The second is A. c. 'River Dee' and I grow it at the front of the border as it only gets to 35 cm. The young new foliage is orange, maturing in the centre to a creamy yellow-green with a light green edge around the leaf whilst it has really deep violet flowers in September – October.
I keep these plants well-watered if we have a dry period in June and July which helps to keep their lower leaves looking good for the autumn. As these plants are all toxic, I do wear gloves whenever I handle them i.e. cutting down in winter or when propagating them.
If you don’t have many aconitums, then I suggest you find room for some more, you could have them flower from May until October / November.
First published in the Ranunculaceae Group Newsletter Autumn 2012
and subsequently in Cornucopia Issue 32.
© Copyright for this article: Sue Ward
This article was taken from a copy of Cornucopia that was published in 2013. You could be reading these articles as they are published to a national audience, by subscribing to Cornucopia.