Two words that seem to trigger instant depression for gardeners: dry and shade. Yes, of course, plants need water and light to grow, but some can do with less. In some ways dry shade can offer opportunities that more clement growing conditions might not.
To start with we need to identify what sort of dry shade we are dealing with and then move forward pragmatically. Note all dry shade is made alike. Sometimes it is the result of a wall that cuts out light and creates a rain shadow or alternatively it may be created by nearby trees or shrubs that shade the ground and rob the soil of all its moisture.
This is not rocket science; to start with if there is a way of improving the growing conditions then do so. By removing the trees, shrubs or nearby buildings and you will be able to grow a wider range of plants, but ….
A less radical approach might be to lessen the shade by pruning nearby plants by either thinning their crowns (in the case of trees) or by raising their crowns, especially when faced with wide spreading shrubs that have branches low down. The more light that filters down to the ground the more vigorously any plants found there will grow.
In soil riddled with the roots of nearby shrubs and trees it will be very difficult to establish new plants, but if this is not the case you should always try to improve the soil by incorporating garden compost. Surface mulching can also help, but care is needed as this can easily suffocate the root systems of the existing plants.
Once you have done all that is possible to improve the situation the question remains – what can I find to get to grow?
The point of this post is not to point you towards all the plants commonly recommended for shady conditions as there are plenty of gardening books around that will do that for you, including my own eBook on perennial meadows for shady situations (see side bar). Most of the plants recommended are adapted to woodland or woodland edge growing conditions and tend to take advantage of light and moisture available to them in spring before the foliage canopy closes above them. Many useful bulbs and ground covering perennials such as pulmonarias will appear in these list.
My aim is to suggest some other perennials that should also be considered even though they are regarded by most gardeners as aggressively spreading species that are better avoided. The point is that these vigorous plants that in normal border situations tend to overwhelm anything else growing nearby are tamed by the constraints imposed by limited soil moisture and shade.
Two genera I have found particularly useful in clothing the ground experiencing dry shade are Aster and Lysimachia. Some species within these genera are notorious spreaders, for example Aster machrophyllus (now Eurybia machrophylla) and Lysimachia cilliata, but in less favourable growing conditions they survive, gradually spread, tend to be lower growing and although they don’t flower as well as in the open border, they bring foliage and colour where otherwise nothing more exciting than green ivy or vinca could be expected to grow.
Pragmatism is the most appropriate approach to establishing plants in the wide range of growing conditions we tend to define as dry shade. Never put all your eggs in one basket; plant a range of different plants all of which you hope will grow and don’t be surprised when only some of them survive. Let the garden lead you towards an appropriate solution.
And finally, please don’t expect even the most vigorous of perennials to establish themselves in dry shade without being cosseted in their first growing season. They will need regular watering even when it has been raining. Once fully established it is amazing what some plants can tolerate, but to start with, they have to be given the best chance to form a strong root system.