Could you please provide suggestions for hostas that will tolerate afternoon sun in Zone 4/5 planted in treated clay soil
Thank you for bringing your garden question to Toronto Master Gardeners.
I admire Hosta for its reliability as a structural plant in the perennial garden. Most of my back yard in clay soil Markham is a Hosta Haven. When I plant, I make sure to tease out the roots and add extra organic material to the planting hole.
As a general rule, light coloured (yellow leaved) Hosta and fragrant Hosta can tolerate more sun than others. Even for these, more than 6 hours of direct sunlight can be stressful. In order to give them the best chance of survival, keep them mulched and well watered. If you can provide some dappled shade from a brightly contrasting shrub or a trellis with vines, your Hosta will fare better.
Earlier this month I found a brilliant Hosta called ‘Designer Genes’ at the Toronto Botanical Garden plant sale. The leaves are a lemony yellow and the stalks are a bright rhubarb red. I paired it with a red leaf begonia and other interesting plants. If you cannot find this one, I am sure that you will find many others as new introductions come out every spring.
There are some excellent books and resources on the topic of Hosta cultivation in bookstores and libraries. One of my favourites is The Color Encyclopedia of Hostas by Diana Grenfell and Michael Shadrack, with a foreword by His Royal Highness the Prince of Wales.
Good luck with your Hosta.