Most bedding plants treat a Canadian spring as a personal insult. Pansies treat it as an invitation. They bloom while the tomatoes are still sulking indoors, shrug off frost, and then, just when everything else hits its stride in July, they wilt dramatically like a Victorian heroine who has been handed the wrong teacup. Understanding why is the key to growing them well.

Why pansies love the cold

Pansies are built for shoulder seasons, and the research explains why. They flower faster as the days get longer, and faster as temperatures rise, but only up to about 22 Celsius. Bright light speeds things along too.

The catch is flower size. As growing temperatures climb, pansy blooms get steadily smaller, a trend that holds all the way from 9 to 31 Celsius. So the long, cool days of May give you big, plentiful flowers. The hot days of July give you small, sad ones and a plant that looks like it needs a lie down.

Starting from seed

Pansy seed wants to be kept cool, since it germinates poorly in the heat. Start seeds in a cool room rather than on top of the fridge, and cover them only lightly. Most gardeners, reasonably, just buy transplants and spend the saved time admiring them.

Planting: spring and fall

Plant in early spring as soon as the soil can be worked. Pansies are frost-hardy, so there is no need to wait for the May long weekend.

Fall planting works too, and late summer to early fall is a fine time to tuck some into containers and beds. Just keep your expectations about winter realistic. In freezing trials, pansies that had never been gradually exposed to cold all died at −15 Celsius, while plants hardened off to the cold survived to −18. The lesson: plants that get a slow, natural cooldown in fall stand a much better chance than greenhouse plants set straight out into a cold snap. On the Prairies, where winter regularly laughs at −18, count any spring survivors as a pleasant surprise.

Soil, pH and black root rot

Black root rot, caused by the soil fungus Thielaviopsis basicola (now also called Berkeleyomyces), is the most troublesome disease of pansies in greenhouse production, and it sometimes comes home with nursery plants. Infected plants look stunted, yellowish or purplish, and the roots show dark bands instead of healthy white. Most gardeners who meet it simply decide the plant was a dud. The fungus is less of a problem in slightly acidic conditions.

If your garden soil is on the alkaline side, as many Prairie soils are, grow pansies in containers filled with fresh potting mix. Never reuse soil from a pot where pansies died mysteriously, and don’t overwater. Pansies want to be moist, not marinated.

The summer slump

When the heat arrives, you have three options. Give plants afternoon shade and keep them watered to carry them through. Cut back leggy plants by about half and wait for cooler weather in late August. Or pull them without guilt and replace them with something that enjoys July. All three are respectable choices.

Deadheading throughout the season keeps plants producing flowers rather than seed.

Eat them

Pansies are one of the few bedding plants you can put on a cake. The flowers have been confirmed non-toxic as food, and colour matters: red, dark red and dark purple blooms carry the most vitamin C, anthocyanins and polyphenols, while white and pale flowers carry the least. Violet and yellow bicolours also beat plain yellow. In other words, the dramatic dark ones are the better snack.

Only eat flowers you grew yourself without pesticides. Nursery transplants may have been treated with products not approved for food crops, so give purchased plants a few weeks of new growth before harvesting.