Geranium bicknellii

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Compared to many members of the Geraniaceae Group, I’m relatively new at growing geraniums. I have had a handful of species in my garden for quite a few years, but it was only in 2009 that I seriously started to collect and study hardy geraniums. Over the last few years, my collection quickly grew and now floats around the 200-variety mark for geraniums, plus over a dozen erodium species. Here in Ontario, we are decades behind the UK and Europe in the availability of new hardy geraniums. Thank goodness for the various group seed exchanges!

My main interest for 35 years had been with indoor plants, specifically the gesneriads (African-violets, sinningias, streptocarpus, etc.). Around 2005, it was time for a change and I wanted to spend more time in the outdoor garden. We have a one-acre property (Growin’house) with more garden beds and less lawn every year. Having always been involved with local horticultural clubs and field naturalists, hardy geraniums seemed to fit nicely with both areas of interest. There are a few species that are native to Ontario, although they are little known amongst the local wildflower enthusiasts. I soon learned that I can have all the same fun with the geraniums that I have had with gesneriads – growing from seed, photographing, and reporting about what I learn through slide presentations and articles in club newsletters. Of course, there is always the thrill of the hunt…and trying to acquire new species and varieties.

There are a few alien species that have shown up in my garden – Geranium robertianum, G. pusillum, and Erodium moschatum, which are not all that garden-worthy, but I allow them a spot in the wilder areas for interest. I have found a few types of Geranium maculatum at garden centres, but have yet to find that species in the wild. Another member of the Maculatum Group that I really had wanted to locate was Geranium bicknellii. I had read in a locally-produced booklet about the alvar specialty plants of central Ontario that Bicknell’s geranium was amongst the plants listed as growing in the nearby Carden Plain, about an hour’s drive from Midhurst.

Worldwide alvars are known to occur in Canada, Estonia, Ireland, Sweden, and the United States. The Great Lakes area of Ontario contains 75% of the Alvars in North America. Alvars occur on flat limestone or dolostone bedrock and soils are thin or absent. The environment of an alvar is harsh, they can be prone to flooding, and in the summer they are hot and dry with temperatures that can reach 43ºC at the rock surface. When the winter winds blow, they are very cold areas with frost and ice crystals churning up what little soil there is. Few plants can survive such a habitat, but Bicknell’s geranium is one of them.

This geranium has a range across North America from California to the Canadian prairies, to much of the east coast from Virginia to Nova Scotia. Here in Ontario it is rarely seen; it is not a showy plant and is not in bloom long, so it is probably not noticed as much as a lot of other wildflowers. Naturalists flock to the alvars of the Carden Plain to see and photograph the abundant drifts of Prairie Smoke (Geum triflorum) and Indian Paintbrush (Castilleja coccinea) in season, but I’m sure they are not as careful stepping around young Bicknell’s geraniums. In the average person’s mind, the showy plants are considered wildflowers and the less showy are regarded as weeds.

On my first visit to the alvar at the end of May, when these better-known wildflowers were putting on their show, I did manage to find a few plants of Bicknell’s geranium, but they were all young plants not yet producing any bloom. They were growing in very thin areas of dark soil that almost resembled regular peat-based potting mix. A return visit in July allowed me to find a few plants with some seed that had not yet been ejected. The foliage of the plants was very red, as might be expected with many geraniums in autumn. The soil on the limestone pavement was bone dry. It would seem that Bicknell’s geranium must grow fast, mature, and set seed before the baking heat of mid-summer on the alvar does it in!

Just north of the Carden Plain, the limestone pavement meets the exposed granite outcrops of the Canadian Shield area. I also did a little exploring around Georgian Bay where I found a few plants of Bicknell’s geranium that had grown in pockets of soil between huge granite boulders. They too, had finished flowering and were already starting to die back in mid-summer.

This fast growth from germination to setting seed is only one method that these geraniums have for surviving in difficult situations. They have the ability to store seed in the ground and have it germinate many years later when conditions suit it – like the better-known Geranium bohemicum, Bicknell’s is associated with fires and they are often one of the first plants to be seen colonizing after a fire. Stored seeds are stimulated to germinate by fire-induced high temperatures. This has been studied and there have also been greenhouse tests where higher germinations have occurred after exposure to higher temperatures (moist heat, water bath). Progressively higher germination happened above 40 to 45ºC, with 90% germination after 10 minutes exposure at 65 to 100ºC.

In nature, seed germination can be triggered by the soil warming when the forest canopy is removed. Of course, the alvar easily produces high temperatures for germination. This all suggests that germination of seed for the gardener might be sporadic and not all seed may germinate the first try. The plant I grew from collected seed (see photo) produced loads of flowers, which in turn produced a lot of seed, as is typical with annual varieties. Despite the high number of seeds ejected into the garden, very few plants sprouted the second year. This year, I’m trying some fall, in-ground sowing and some winter sowing in containers to see how germination does under more controlled conditions.

It’s these little quirks of some geraniums that makes this hobby so interesting, plus I can go plant hunting in my own backyard, figuratively and literally.

• 28 Feb, 2014
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