Hordijk EPS Packaging & Insulation Products, in collaboration with Tenax Tree Plugs & Seeds, has developed an extra-rigid EPS tray for cultivating young tree seedlings. Thanks to the smart design and the material’s properties, the one-year-old seedlings can grow into uniform, high-quality young trees.
Tenax Tree Plugs & Seeds, based in Rijsbergen (NL), cultivates a wide variety of tree seedlings for ornamental horticulture and commercial forestry across Europe. “Just for Douglas fir alone, which is used for roofing and terraces, we grow nearly 2.4 million seedlings,” says owner Niels Dictus. “We also grow larch, beech, small Christmas trees, and Japanese asters for ornamental use. In total, we produce 70,000 EPS trays and 10 to 11 million seedlings per year.”
Supporting optimal growth
The plants are cultivated in long tunnels, each holding more than a thousand reusable trays. The trays (40 x 60 cm) are pressed extra hard. “That’s very important,” Dictus explains. “A tree develops a taproot and lateral roots, which are very strong. If the tray isn’t dense enough, those roots will quickly grow right through the material.” The insulating properties of EPS also help protect the fragile young plants. “With black plastic trays, you often get root burn on the sun-exposed sides. EPS keeps the heat out on hot days and protects against the cold in winter. It also retains some moisture from the potting soil, which is gradually released back to the plants.”
The generous depth (8 cm) and the specific shape of the cells also help the seedlings thrive. “The inside of each cell is slightly tapered and has small ridges to prevent the roots from circling,” Dictus explains. “When roots hit the edge, they are redirected downward.” Because the tray’s drainage holes are open at the bottom, every root comes into contact with air and light. “Air in particular is crucial. It triggers a kind of root pruning, which encourages the formation of fine feeder roots. That’s essential for regrowth once the trees are planted. A tree will be in the ground for decades, so everything has to work perfectly.”
A collaborative design
Tenax initially purchased similar EPS trays from another supplier. “But I thought: wouldn’t it be more cost-effective to have a custom mould made?” Dictus recalls. “Eventually I just typed ‘EPS’ into Google and found Hordijk. After several meetings, technical drawings, and a test print, we arrived at this great design together.”