I mulched with clean leaves (mostly maple) in the fall: hydrangea, digitalis, some other bits I don’t remember. The intent was to replace the snow cover we don’t seem to get in Toronto anymore. I know mid-march is too early for removal of the mulch, but I am wondering if you can suggest some guidelines so I don’t leave the leaves on too long.
Thank you for contacting Toronto Master Gardeners.
Leaves are great way to help protect the garden from the affects of freeze thaws in the winter. Leaves also help replenish nutrients and structure of the soil and leaf molds are beneficial to the health of the soil. Leaf mulch is also used by many beneficial insects for over wintering their eggs.
When using leaves it is important to ensure no leaves are included from any plants that may have been diseased during the previous season as infections can over winter in the leaves. To get the maximum benefit from the leaves you can mow them into small pieces before top dressing your garden. By doing this you can leave the mulch on the garden and let it break down and replenish the soil.
If the leaves are just raked on you will need to remove them at some point. It is difficult to set a specific time as each year as the timing changes. If you have tulips and other early flowers you will need to clear it off so the can grow unhindered. It is a matter of looking at the weather and guessing when the last hard frost will be. Most damage to roots comes from large temperature variations freezing and thawing the tissues.
Below I am including a guideline from the Toronto Botanical Gardens on when different tasks should be done in our area. It lists March for removing mulch but with the low temperatures we are experiencing it may be a bit later this year.