Last summer's floods left behind a trail of destruction in High River and deposited plenty of toxins in the southern Alberta town's soil.

Now some people are trying to purify the ground using sunflowers.

Seeds are being delivered to every mailbox in town, all in hopes of purifying the soil using a technique called phytoremediation.

Marcus Samuel

University of Calgary botanist Marcus Samuel says sunflowers are particularly resilient and suited for phytoremediation, but High River residents should not eat the seeds. (Devin Heroux/CBC)

While it might sound complicated, botanists say it's really quite simple.

"Essentially what you're doing is using plants to suck up all the toxic waste from the soil into the plant," said Marcus Samuel, a botanist with the University of Calgary.

The plants will have to be cut down and thrown away after sucking up the toxins — and Samuel warns residents definitely should not be eating the seeds.

It's also a low cost option compared to expensive soil remediation treatments. The technique was used successfully in New Orleans after Hurricane Katrina in 2005.

Sunflowers can absorb many different toxins and chemicals from the soil and then store those chemicals at the cellular level. Once they're absorbed, they won't leach back out again.

Not all plant species can handle absorbing all those chemicals — many would die from the heavy metals in the soil.

But given the huge biomass and rapid growth of sunflowers, they can isolate the chemicals and continue to grow, Samuel said.

Sunflowers a 'ray of hope' for residents

CBC News hired Benchmark Labs in September 2013 to test soil from six residential locations around High River.

Two of those samples came back positive for the dangerous E. coli O.157 strain, which is commonly found where there is runoff from livestock operations.

Susan Lukey

Susan Lukey is a church minister with the High River United Church, which has been collecting sunflower seeds to send to local residents. (Devin Heroux/CBC)

No one was infected with the bacteria but many residents were left worried about the safety of their backyards and lawns.

So far 18,000 sunflower seed packets have been collected, far exceeding the 4,000 mailboxes in High River. And organizers plan to mail some out to other flood-affected communities next week.

The project is being co-ordinated out of the High River United Church.

"I mean, they rejuvenate the soil but also it's the brightness of them," said church minister Susan Lukey. "It's just like a ray of hope."

The process will take some time and residents might have to keep planting the sunflowers over several seasons.

Residents in Black Diamond, Turner Valley, Canmore and Calgary will be getting their own little packets of sunshine soon.

With files from CBC's Devin Heroux