Spring in Ottawa is like a game of "Red Light, Green Light" with Mother Nature. One day you’re wearing a t-shirt, and the next, you’re scraping frost off your windshield. Knowing when to put your green friends in the ground is the difference between a thriving garden and a frozen heartbreak.
So, the question is... WHEN CAN I PLANT?
Our answer; it depends on what you are planting! There are two main barriers in the spring that can delay planting; ground thaw and morning frost. The ground thaw is an obvious barrier as if you cannot dig, you cannot plant. Frost damage isn’t as linear as a ground thaw and can occur as late as June. Luckily, you can use products like frost blankets or sprinklers to mitigate frost damage. Frost damage actually occurs early in the morning, typically right before dawn. Gardeners who wake up early should consider leaving frost blankets on their gardens or planters until after sunrise; between 7 and 8am.
Overwintered or dormant trees, evergreens, and shrubs can be planted when the ground has thawed! The best time to plant Dormant Trees and Evergreens is as soon as the ground is "workable"— meaning it’s no longer a block of ice and isn't a muddy soup.
If you can push a spade into the earth and the soil crumbles rather than sticking like clay, you’re good to go! These plants are still sleeping (dormant), so they don’t mind the chilly air as they wake up in their new home.
Aim for soil temperatures around 7°C to 10°C to trigger root respiration without forcing immediate canopy growth. Planting early allows the root system to establish before the summer heat hits, reducing transplant shock.
Cold-tolerant annuals like pansies, kale, cabbage or dusty miller can be planted once the ground thaws and the plants have had a chance to “harden off”. If you’re buying from a greenhouse or have raised these plants from seed indoors, you may want to transition these annuals to the outdoors over a couple of days. This helps the plants acclimate to more sun, wind, and cold temperatures better than direct planting.
Eager to get started on your perennial gardens? Most Perennials follow a similar "workable ground" rule, but with a slight twist depending on how they’ve been stored.
If you bought a perennial that is currently just a pot of dirt with a few tiny nubs (overwintered), it can go in early. However, if it’s already lush and green, i's likely been in a warm greenhouse all spring and will need a slow introduction to the Ottawa breeze.
Any plants with new flowers should only be planted AFTER the risk of frost has passed. Leaves and blossoms that have been forced by greenhouse heat are significantly more tender to the cold and direct sunlight than overwintered outdoor plants. If you’re unsure, just ask one of our garden experts when they would ideally plant!
Annuals, seedlings, and new flowers should only be planted AFTER the risk of frost has passed. In Ottawa, this is usually between the last week of May and the First week of June.
If you want to add hanging baskets or potted arrangements outdoors, you can always bring them out for the day and shelter them in a garage or under a frost blanket at night. This will help ensure that your blooms aren’t damaged by frost overnight.
The best advice we can give to new gardeners is that it is often best to JUST ASK. We are always happy to give advice to gardeners looking to grow healthy plants.