Soil improvement worthwhile for Liquidambar ‘Slender Silhouette’ [gumtree] and Dogwood Cornus ‘Eddie’s White Wonder’


Hi, I am in Leaside, Toronto and two years ago put in a new plant bed, with soil and compost additions, at the north end of the garden. Sun is at least 6 hours per day, the garden is naturally clay with poor drainage.
Two trees – Liquidambar ‘Slender Silhouette’ and Cornus ‘Eddie’s White Wonder’ are not doing well. Yellowing of the leaves of the gumtree this summer suggest that soil ph is a problem. The cornus had one flower, few leaves and mould. I spread compost around the trees each Spring and wathered regularly this summer. This fall I used a a tree service. They added granular elemental sulphur and organic feed.
Other trees in the area are an old swamp cedar hedge, A black locust, and a thriving ‘Maackia amurensis ‘MackNificent’ planted at the same time.

My question is: is it possible to amend soil sufficiently so these lower soil pH-requiring trees thrive in Toronto soils or were they just a bad choice for the garden. Unfortunately I this time leaves have fallen and I don’t have any useful pics.



Thank you for contacting Toronto Master Gardeners regarding soil amendment for your trees.

Your tree selections of Liquidambar ‘Slender Silhouette’ and Cornus ‘Eddie’s White Wonder’ are good choices for clay type soil and the amount of sun they receive. However, while you describe the area as having poor drainage, the pre-planting steps taken to improve drainage are unclear. The preparation of both the area and the root ball of the trees as well as the method of planting are critical for the health and longevity of trees and other plants. Poor drainage is problematic for most plants as excess water deprives the roots of air and leads to root damage which may be the reason for your trees not flourishing. While soil pH may temporarily be amended by top dressing with organic matter, pH is much less critical to plant health than drainage. The health of these trees is uncertain unless drainage is/or can be improved.

For more information on garden drainage, click here

For pH testing prior to amending, click here

Wishing you the best with your new garden and trees.