Bio R tree-planting at Frahn's Farm, Monarto, considers science of pollination, bird food sources | PHOTOS, MAP

Tree-planting is a worthy exercise for anyone concerned about the environment, but it is the science behind it that could make all the difference in the long run.

On Sunday at Frahn's Farm, at Monarto, dozens of volunteers nestled more than 2500 seedlings into holes.

Rather than dropping any old species into any old hole, though, they stuck to a plan laid out by PhD student Kimberly McCallum, who is researching the effect of clustering each species together.

The original Monarto plantings – undertaken after the failure of the state government's planned city in the 1970s – were haphazard, leaving long distances between trees of any given species, fewer chances for bees to carry pollen between them, and fewer viable seeds.

Another student, Hayley Merigot, will look into whether blue gums can be made to flower all year round, instead of for just two months at a time.

She took seeds from eucalypts from locations around the Adelaide Hills where they flower at different times: winter at Belair, spring at Currency Creek and summer at Cromer, near Mount Pleasant.

She hoped they would continue to flower at those times even when planted in a single location, thereby providing year-round sustenance for the birds which feed on their nectar.

The project will be a long-term one – the seedlings will not be mature enough to flower for six to 10 years.

A third student, Grace Hodder, focused on one particular bird which had struggled to find enough food in recent years: the diamond firetail, a finch with spotted wings and a brilliant red beak and tail.

She set up plots of the grass they prefer to eat and will monitor them to see whether the birds come and visit.

But why would the volunteers, mostly from Adelaide and many with children in tow, choose to spend a cloudy Sunday carrying seedlings all over a paddock and hammering in stakes and shelters?

For the greater good, suggested Lyn Belder, who came with her husband from the city's south-eastern suburbs.

"Too much land has been cleared for farming," she said.

"Habitat loss has resulted in a loss of wildlife.

"In order to get it back, restoration has to happen.

"If volunteers aren't going to do it, they aren't going to pay anyone."

The planting day was overseen by not-for-profit organisation Bio R and Natural Resources SA Murray-Darling Basin.