Sun-loving Violets

by Trish Murphy

This article was originally published in OHS News, April, 2018, the newsletter of the Ottawa Horticultural Society.

One of the things we think we know about violets is that they grow in shade, shyly, among mossy rocks. The other thing we think we know about violets is that they invade lawns.

Many species of native violets do grow in moist shady places A couple of species of native violets, notable the Common Violet, will invade lawns, a tendency which you might think charming or a nuisance. What is less well known is that there are violets for dry sunny places, charming little plants that are ideal candidates for sunny rock gardens.

We grow two of the sun-loving violets in the rock garden at Beaux Arbres. The locally native Hooked-spur or Early Violet (Viola adunca) is one of the earliest native flowers to bloom. It is a small plant, only about 2” tall, covered in small violet blooms in early May. The plant is very well behaved – the stem emerge from a central crown each year. It might seed gently in the rock garden – and volunteers are always welcome with us – but the plant is too small to compete with lawn grass.

The second sun-loving violet we grow, Bird’s Foot Violet (Viola pedata) (featured image) is a very special flower from Carolinian Ontario, where it grows in Turkey Point Provincial Park and a very few other locations. It is more widely distributed in the US but it is threatened by habitat loss throughout its range. Bird’s Foot Violet has finely divided foliage, quite unlike that of a typical violet. The flowers, with a prominent yellow central boss, are relatively large for a wild violet. The plant is in bloom for a long period in the spring and will often re-bloom in late summer. Last year, the cool wet weather encouraged Bird’s Foot Violet to be in bloom almost continuously, which is an amazing feat for a native wildflower. This lovely little flower will certainly not invade lawns and is quite shy about offering volunteer seedlings even when we encourage it to do so.

Both of these these violets like full sun in the spring and lean, sandy soil. They can tolerate a bit of shade as the summer progresses, but not too much.

One of the best reasons for growing sun-loving violets, apart from their charming bloom, is to attract and provide food for Fritillary Butterflies. There are several species of fritillary in the Ottawa area and, as caterpillars, they all eat violets, diverse violets but only violets. The smallest species, the Meadow Fritillary seems to seek out violets wherever they are. We often see them laying eggs on or near the Common Violets in the damp end of our lawn. I have had to stop the mower, sometimes giving up on the idea of mowing that day, while the Meadow Fritillaries are intent on egg-laying.
The largest and most glamorous fritillary is called the Great Spangled Fritillary, a very beautiful butterfly, almost as large as a Monarch. Great Spangle Fritillaries are creatures of warm, sun-lit spaces and they don’t seem willing to venture into the shade to find violets. They are so well adapted to dry, sunny environment that they have the ability to discern violets, even if the violet foliage has shrivelled in a dry summer and all that remains are the roots below ground. The mama butterfly will lay her eggs on the ground, in anticipation of the violet’s leaves emerging with damper fall weather.
Great Spangled Fritillaries are quite common at Beaux Arbres, probably because we have so many Hooked-spur Violets growing, not just in the rock garden but abundantly on the dry hills behind the barn.
If you are interested in providing host plants for butterflies, be sure to include some of the lovely little sun-loving violets in your garden plans.