Thai researchers boost tree survival rates with repurposed bottle crates

A team at Chiang Mai University just figured out how to make forest restoration cheaper and more effective — by stealing an idea from how gardeners prevent root rot.

For years, Thai nurseries have grown native tree saplings in black plastic bags laid flat on the ground. It sounds fine until the trees actually grow. The roots spiral tightly inside the bag, tangling and deforming. Worse, they sometimes break through the bag into the soil below. When it's time to plant these saplings into a harsh, deforested landscape, half the root system stays behind in the nursery soil.

"You're putting it at a disadvantage," explains Stephen Elliott, research director at the Forest Restoration Research Unit at Chiang Mai University. "You're immediately reducing the capacity of the plant to absorb water on the day it's being planted into a harsh, dry, deforested environment, where it's going to compete against the weeds."

The fix came from a simple observation: what if you lifted those plastic bags off the ground and placed them inside repurposed plastic bottle crates instead.

This small shift triggers something called air pruning. As roots grow toward the edge of the bag, they meet air instead of soil. They stop extending downward and branch outward instead, creating a dense, healthy fibrous root system. When the sapling is finally planted in the forest, the entire root network comes out intact — ready to absorb water and compete for resources.

The researchers call it the COG system: Crate-Oriented Growing. There's nothing expensive or complicated about it. The crates are recycled. The bags are the same ones already in use. The difference is measurable — survival and growth rates for native tree saplings improve dramatically.

This matters because forest restoration is scaling up globally. The U.N. Decade on Restoration, climate commitments, and the biodiversity crisis have sparked restoration projects across the tropics, many of them community-run. In Thailand alone, thousands of nurseries are cultivating native species for replanting. A technique that costs nothing extra but doubles or triples a sapling's chances of surviving its first harsh years in the field could reshape how quickly these forests recover.

The COG system is already being adopted in restoration projects across Southeast Asia. It's the kind of innovation that doesn't require new technology or significant funding — just attention to how plants actually grow.