What a great idea! I believe that you may want perennials (these are the plants that come back each year) with purple leaves, so will focus mainly on these. Remember that in a shady area, some of these plants might make the garden look quite dark. I’ve also suggested a couple of plants with purple flowers (and green leaves).
Consider the following:
- Heuchera ‘Blackberry ice’, which grows to about 20-30 cm (8-12 inches) in height and spreads 30-40 cm (12-16 inches). There are likely many more Heuchera varieties that would have purplish leaves. These plants generally love shady areas.
- Ajuga reptans ‘Bionblasca’ Black Scallop (Bugleweed), which grows up to 15 cm (6 inches) high and spreads up to 60 cm (2 feet). Its leaves are purplish and its blooms are violet. The plant tolerates part shade. Other varieties of bugleweed are also attractive, and like shade.
- Bergenia ‘Bressingham Ruby’ (Heartleaf)– this plant grows 30-35 cm (12-14 inches) high and spreads 45-60 cm (18-23 inches) and likes partial shade. Its leaves are deep green, then turn a lovely reddish colour and its flowers are small and deep pink.
Landscape Ontario’s Perennials for ground covers has a list of plants, including shade-loving ones, that may be of interest. Although I don’t believe that any have purple leaves, you may find some of these that please you. For example, Alchemilla mollis (common name-Lady’s Mantle is lovely and tolerates a nearly full shade. Its leaves are a beautiful shape and are often covered in dewdrops.
I can’t resist mentioning a couple of lovely plants with green leaves and standout blooms:
- Vinca minor (periwinkle), which has shiny (and pretty) evergreen leaves and purplish-blue flowers in May/June and tolerates partial shade. (Be careful to rein this in, though as it’s invasive).
- As well, Phlox stolonifera (creeping phlox), which tolerates partial shade, is a lovely, long-flowering groundcover – its leaves are green, but its profuse flowers are purple/violet and would show up nicely in a shady garden. It can grow up to 30 cm (12 inches) tall and has a spread of up to 45 cm (18 inches).
See Broadleaf evergreen groundcovers: A Toronto Master Gardeners Guide. This article provides additional ideas for a terrific groundcover.
I suggest that you go to your local nursery take a look at a few plants I’ve mentioned. With perennials it is important to love the leaves, as most are not in bloom for the entire season. You may want to ask someone at the nursery for suggestions – I’m sure there are many other plants for you to consider. And when buying plants for your shady garden area, perhaps buy only 2 or 3 plants of one variety at a time and try these in your garden. If you have deep shade, some may not survive.