To reduce urban flooding, cities build green infrastructure like stormwater tree pits (STP) that divert street water into the soil of a street tree. The tree receives this water, along with high concentrations of de-icing salts, especially in colder climate cities like Montreal. The salt concentration peaks in early spring before active growth, and the effect on various urban trees species is not clear. Furthermore, the city has inquired about the use of biochar as a soil amendment to reduce tree salt stress.

This study has four goals, a) to understand the growth conditions of local STPs, b) to test if tree health and growth are affected by the early spring salt flush c) to find which urban tree species are tolerant (10 urban species tested), and d) to test if biochar can help a tree resist salt. We investigate these questions with a 200+ young urban trees in a pot study, and 18 stormwater tree pits, in a pilot study in the neighborhood of Rosemont-La Petit-Patrie, Montreal.