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When Should I Plant Annual Flowers?

The Victoria Day weekend usually coincides with the planting of annual flowers, but after the cold & wet spring that we’ve received in southern Ontario- when is the right time to plant?

Flowers in green house
Annual flowers are the perfect way to add eye-catching colour and foliage to your garden or planters. Annuals have one long growing/flowering season, and then die off in colder weather (hence the name, since you plant them annually). In comparison, perennials are planted once and return year-after-year, but they have a shorter flowering season.
So although the days are getting warmer, and garden enthusiasts are eager to get outside, when is the right time to plant annuals?

When to plant?

Flowers in green house

The right time to plant annual flowers depends on two things: the specific annual flower and the climate. Annuals are categorized based on their hardiness and ability to survive in cooler temperatures. To find out what climate your garden is in, click here. The average frost-free dates for southern Ontario are between May 1st -10th, which is why the Victoria Day weekend is usually a safe bet to plant annuals. However, this spring has been colder than average, and therefore it’s advised to wait a couple more weeks to plant tender/ tropical annuals. So although the annuals are flourishing inside the warmth of the greenhouse, our current cold spring nights and the potential for frost, would cause them to perish.

Hardy Annual Flowers- grow best in cool soils with mild temperatures, and have the ability to withstand fairly heavy frost. By mid summer hardy annuals don’t thrive as well as tender/tropical annual flowers, and are usually replaced. Hardy annuals are perfect for early spring and fall, with the most common being Pansies.

Tender/Tropical Annual Flowers- grow best in warmer temperatures, and they must be planted after the threat of frost has passed (since they will die in cold temperatures). Tender annuals are usually planted in late spring or early summer, when the nights are warmer. The most common tender annuals are: Marigolds, Zinnias, Impatiens, Alyssum, Coleus, Geraniums, Ageratum, Petunias, and Salvia. 

Annual Flower Light Requirements

Another important detail to think about before planting, is the amount of direct sunlight the annuals will receive. Be sure to always read the information tag for the specifications of that plant. Flowers will not reach their full potential or they may die if they don’t receive the proper light requirements. The majority of annual flowers prefer sunny locations, however there are a few that will survive in shaded gardens.

– Jenna Monk