I have several potted hydrangea and hostas on deck. Should I plant them in ground before winter or wait till spring?
Thank you for contacting Toronto Master Gardeners with your question.
Late summer/early fall is a good time for planting shrubs and perennials. Your plants will do much better in the ground than in pots where they would be very vulnerable to winter frosts. It is best to plant early enough in the fall that the plants have time to establish their root systems before the cold weather sets in. If possible, choose a cool, overcast day for planting to minimize the chance of scorching your plants. Water your plants well, and make sure to keep the soil moist, even in the cooler fall weather. An application of organic mulch around the plants can help retain moisture and will insulate the newly planted roots from winter frosts.
Here is a previous response from the Toronto Master Gardeners on the topic of planting perennials:
https://www.torontomastergardeners.ca/askagardener/when-to-plant-perennials/
The following links are to good general articles on growing hydrangeas and hostas: