These 3 invasive plants may be hiding in your garden. Here's what to replace them with

Londoners may unknowingly be growing plants in their backyards that are causing harm to the local ecosystem, and experts are offering alternatives.

Invasive plants are species that are not native to the area, which have the potential to spread rapidly, using up the natural resources that otherwise keep native plants healthy. They aren't always thick weeds or tall grasses, experts say, but can be the colourful flowers and luscious groundcover hidden in plain sight.

"Usually when I'm looking at invasive species in residential areas, they are plants that were planted there by homeowners," Eldon House grounds and garden co-ordinator Kendal Davidson said. "They're not really something that creeps in. They're usually something that's put there for landscaping because people don't have the information."

Many of these plants are sold in nurseries and grocery store garden centres, Davidson said, often advertised as low-maintenance garden choices.

"Unfortunately, the characteristics that make them low maintenance are also a reason that they're classified as invasive, because they don't need a lot of inputs and they spread aggressively," she said.

The abundance of invasive plants not only makes it harder for native plants to access sunlight and nutrition, but also has a domino effect on the city's surrounding wildlife, said Forest City Native Gardens founder Jonni Deetjen.

"When invasive species come in, they crowd out the native plants and it just reduces the amount of food insects can eat and reduces the overall food web," Deetjen said. "Biodiversity goes way down."

Experts told CBC News some of the invasive species they see most often in homeowners' yards, and what plants would be better replacements.

Officials at the Invasive Species Centre, an Ontario non-profit, say one of the most common groundcover that gardeners use is periwinkle, which has a purple star-shaped flower among leafy foliage.

"They form very dense mats along the ground, and these mats do not know boundaries, so they will continue to strike if they are not contained," terrestrial invasive plant co-ordinator Monica Liedtke said.

Davidson said she sees periwinkle all over the city.

"I live in north central London, and I would say approximately every third house has this growing somewhere on their property," Davidson said.

She suggests Londoners consider planting woodland phlox as an alternative, as they share the same blue flowers and leafy groundcover as periwinkle.

For a more versatile option, Deetjen recommends Londoners plant woodland strawberries, which grow small white flowers that spread across the ground, alongside the edible fruit.

English ivy, also called common ivy, is an evergreen vine with bright green leaves that is constantly on the move.

The vines grow quickly, creeping up on trees, winding around fences and going down slopes, Deetjen said.

"It'll climb up the trees and make it super heavy in the winter, so when snow falls on it, it can bring the trees down," she said. "It'll just out-compete any native plants in the area."

A good leafy alternative is Canada wild ginger, according to Davidson, which grows low to the ground with bold foliage.

For people looking to keep their English ivy, Liedtke said Londoners can transport the plant into a pot to prevent it from spreading.

Deetjen is in the middle of a bamboo-removal project in London, which she said is threatening more than the local ecosystem.

"The root system is super dense and it's threatening the foundation of this woman's house," she said. "It grows through concrete sometimes, so it's a pretty intense plant."

That makes it challenging to get rid of, she said.

"Bamboo can be a tedious process where you have to come back multiple times, remove new shoots and reapply herbicide," she explained.

Once bamboo is removed, a different tall plant, like the red osier dogwood can act as a privacy hedge for Londoners.

Other common invasive plants include goutweed, yellow archangel, Japanese knotweed, ditch lilies and lily of the valley.

"I find that for a lot of these plants, people have emotional connections to them. I know a lot of people who have childhood memories of lily of the valley because of the scent of it," Davidson said.

There are nice alternatives for the flowers, experts say.

Instead of the orange ditch lilies, Londoners can try out butterfly milkweed, which is the same bright orange and tends to attract monarchs. Other colourful native flowers include the woodland sunflower, dense blazing star and joe pye weed.