Is it o.k. to start transplanting perennials in downtown Toronto now (Sept. 10)?
Warm daytime temperatures, greater frequency of rain, shorter days, and cooler nights make fall the perfect time to transplant perennials. The key to transplanting in the fall is to plant early enough in the season to allow for proper root establishment, at least 3-4 weeks before a hard frost.
That being said some plants transplant better in the spring and some better in the fall. And while there are exceptions, the general rule is that if it blooms in the spring,transplant in the fall. If it blooms in the summer or fall, transplant in the spring.
Anytime a plant is transplanted it suffers some root loss which reduces the plants ability to up take water. As a result, when transplanting it is best to cut the plants back by one-half to two-thirds to reduce transpiration (water loss). This allows the perennials to utilize their energy towards root production rather than into supplying water.
Once transplanted make sure to apply about three to four inches of mulch around perennials. This helps to retain the moisture and keeps the ground warmer, promoting root growth well into the late fall.
You may wish to refer to the following website: Fall’s a Good Time to Transplant Perennials
Have fun playing in your garden and enjoying the beautiful days of autumn.