I live near Lake Ontario. Have a small yard with large tree. and raised garden against back fence. Have never been able to establish plants for any period of time except a burning bush. A lilac bush cutting has only grown about an inch in 2 yrs. DIY test suggests quite alkaline soil. Am afraid to do anything drastic. Suggestions? Diane


Thank you for contacting the Toronto Master Gardeners with your gardening inquiry.

Physical characteristics such as soil quality (including nutrients), available light and the amount of moisture present in your garden, determine the extent to which your plants will thrive. So, testing your soil was definitely an excellent place to start. In a nutshell, you have a couple of options. The first is to try and work with your existing alkaline soil. The second, is to amend the soil and make it less alkaline (that is, more acidic). Some plants will thrive in more alkaline soils, some will thrive in more acidic soils, while others require a more neutral soil.

Working with your current soil is probably the easiest option in terms of overall cost, and physical labour. Given that your soil is alkaline, you could try sourcing plants that thrive in alkaline environments. Depending on where you reside along the shores of Lake Ontario, some soils in this region are derived from dolomitic limestone and sandstone, and exhibit characteristics similar to “chalky soils”.  This article from the Royal Horticultural Society in the UK, provides some general information on chalky soils as well as the types of plants that can thrive in these types of alkaline environments.  Many of these plants are available here in Toronto, and you could ask at your local nursery whether they have any native plant specimens that would be suitable for your site.  Alternatively, you might find interesting results on an internet search, with key terms such as “plants that thrive in alkaline soils”.

Your second option is to amend or change the pH of your existing soil. This article is a great introduction to explaining alkaline soils  and how to fix them. Should you decide to go ahead and amend your soil to make it more neutral or even slightly acidic (pH 6-7), Toronto Master Gardeners suggests considering some of the non-invasive native plants recommended in this publication. In addition to the soil’s pH, it is also important not to overlook the soil’s nutrient levels. This hyperlink is a great introduction to understanding and solving nutrient deficiencies.

Very best with your garden project.