‘Pillowcase” structures to limit new tree growth

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Making space. . . Gore District Council parks and recreation operation supervisor John Ave (left) and Newton Excavation owner Dane Newton watch as council machine operator Darryl McClenaghan shovels away shingle to make room for the next row of plastic cells. The cells are part of a structure to limit the growth of the roots of a tree which will be planted in the hole. PHOTO: SANDY EGGLESTON

Large pillowcase-like structures buried underground will stop trees from outgrowing their site in Gore’s Main St.

Last week the structures were fitted into the holes where previously dawn redwoods had been planted.

The redwoods, which were causing infrastructure damage and impacting overhead wires, were cut down at the end of last year.

The system comprises plastic cells which are fitted together to make an underground load-bearing matrix.

This is then covered in a large geotextile fabric.

The tree is planted in the centre.

Gore District Council parks and recreation manager Keith McRobie said the structure provided a space for the root ball of the tree to grow.

“It’s a fully enclosed root system essentially like a large pillowcase.”

Next week Malus tschonoskii(pillar crabapple) would be planted in the prepared space.

“They are a pyramid shape so they are not going to grow as large as the previous trees and we’re putting them in slightly further into the carriageway so they’re away from the overhead wires.”

About 9cu m of topsoil and compost had been filled in around the structure.

“There is lots of opportunity for the tree to grow properly.”

The trees would be about 2m tall when planted but would grow to between 6m-8m.

The geotextile fabric cover would last for about 50 years, Mr McRobie said.