Nurturing the trees of the future
The saying ‘necessity is the mother of invention’ could be coined to describe the City of Onkaparinga’s nursery.
The city’s nursery is flourishing, producing thousands of healthy seedlings and saplings each year for planting across the region — streets and parks, creeks and foreshore — but 10 years ago it was a different story.
A number of the city’s native trees and shrubs were lost during the drought, and with many plant suppliers also struggling to survive the drought, a dry and hot landscape was forecast.
Action was needed. As was an innovative and sustainable strategy.
The council’s Parks and Natural Resources team undertook research and planning, with expertise and educational resources provided by the Waite Institute and Adelaide Botanic Gardens. This was boosted by federal funding which enabled the council to establish a nursery with capacity to grow 80,000 seedlings a year, expanding to produce 3500 trees annually.
Today, the future looks more palatable. More green.
Already the dense tree-planting program is evident, with pocket forests springing up in many public reserves.
“We are planting intensely to showcase a variety of different species across the council area,” explains Ian Seccafien, Senior Urban Forest Officer. “If people want to see a community of jacarandas, go to Ormiston Road, Morphett Vale, or eucalyptus sideroxylon feature at Pembroke Street, Reynella. We have about 10 pocket forests established, with 12 more to come. They have paths to wander along, adding another recreational activity to our parks.”
Research identified that Onkaparinga was deficient in tall trees. Top points for medium and small plants, but large long-living trees were scarce on the ground.
This germinated the legacy tree program, with large trees such as redgums, Moreton Bay figs, oaks and maples planted in large public spaces. Although the origins may differ — some are native, others exotic — the trees share one common characteristic: they survive for hundreds of years. But selection is critical.
“That’s what makes the Waite Arboretum’s work with legacy trees so interesting,” says Rinus Bouwer, Team Leader of Parks and Natural Resources. “These trees have not received a lot of maintenance or water over the last couple of decades, yet they are thriving, which is a very good indication that they are resilient and can survive in our climate. A lot of oak trees come from Mediterranean areas with a similar climate to ours — dry, hot summers and wet, cold winters — and are ideal to establish on our parks and reserves.”
Underpinning all planting programs is a ‘whole of life’ tree management strategy. Seeds are harvested from healthy plants, then nurtured in the nursery before they are planted. The care of the saplings continues when in the ground: they are professionally pruned and shaped, repaired when damaged, watered when thirsty, and given the best start to ensure they are healthy and resilient throughout their lifecycle.
Another key research finding was that the city needed greater plant diversity. Lessons learned from America and the UK were heeded, where a monoculture of trees was lost when pest and disease hit.
Biosecurity lessens this risk, Ian says. “Providing balance with other species is important. The nursery industry as a whole does a lot of research, which helps us select a good variety of species that are drought and disease tolerant, and are a good quality tree for our climate going forward.”
As well as plants, the nursery cultivates strong community relations. “About three years ago we established a successful volunteer program,” Rinus explains. “The volunteers work with the plants until they’re healthy seedlings, which helps us produce good quality and quantities, and in turn we transfer some of our horticultural skills to our community. We couldn’t run the nursery without the volunteers, so they are hugely valuable to the program.”
FROM SEED TO SAPLING
Ian Seccafien and Danny Crozier, together with the Urban Forest team, plant legacy trees at Serpentine reserve in O’Halloran Hill; a thriving two year old pocket forest; native seeds are extracted from pods by volunteer Noel Pearson; the nursery’s oak seedlings.