Thrillers, spiller and fillers: Pretty planters have a formula at city's Springbank greenhouse

Thousands of flowers are in bloom at the City of London's greenhouse, in their final weeks of growing before city staff move them to various parks, streets and planters next month.

The mostly red, pink and purple flowers will soon beautify the city as the weather gets warmer and Londoners spend more time outside.

"Every year, we try to choose a colour palette across the city," said Caitlin Bye, a horticulture supervisor for parks operations at the City of London. "We usually try to keep everything as coordinated as possible."

Between January and the end of May, a team works to grow 25,000 annual plants in a greenhouse at 645 Springbank Dr. All of the plants start as a seed or cutting, and are watered every day for five months, said Bye.

"The key component is making sure nothing dries out, so it's a pretty delicate balance of making sure we're not overwatering or underwatering," Bye said, adding that the crew also adds fertilizer to the plants when necessary. "Then, the greenhouse and the sunshine do the rest."

The greenhouse, part of the city's Civic Garden Complex, has an automated system which opens or closes the vents and curtains based on the weather conditions, Bye said.

Following the last full moon in May, city crews spend two weeks planting the flowers and foliage in places like Springbank Park, outside London City Hall, at the Elsie Perrin Williams Estate and around community centres, for Londoners to see.

Depending on where Londoners are looking, they will encounter different plants based on the amount of sunshine in the area, Bye said.

"We typically are tailoring our pots and garden beds to whether it's a shady area or sun-loving area," she said. "In our shadier areas, we're going to plant things like begonias that are going to be able to grow and continue to flower in the shade."

There is one thing that Londoners may notice is the same across planters, Bye said: they all contain, what she calls, a "thriller, filler and spiller."

"We have this rule where you want to have a thriller, which is a tall plant in the centre; a filler, which is going to be something that fills the planter and is typically flowering; and then a spiller, which spills over the pot and gives you that nice cohesive ground-and-up feel."

A dedicated watering crew and irrigation systems help keep the plants thriving when they're out in the city over the summer, Bye said, adding that they usually last until Thanksgiving before the city collects them for composting.

"Enjoy them. They're there for everyone to see visually and enjoy," Bye said.