Grow narrow, grow flexible — a slim single-cell modular grow tray designed for herbs, greens, and mixed growing configurations within the LGP ecosystem.

The LGP Single Cell ThirdTray is a fully 3D printed single growing cell with an 80mm deep chamber, a removable humidity dome, and a 2-stage wicking system for bottom watering. It fits exactly one third of the LGP Self-Watering Tray — three ThirdTrays fill the full reservoir, or mix and match with other LGP ThirdTrays for different varieties side by side. It also works completely standalone on any surface.

The slim single cell format is ideal for herbs, greens, and plants where you want individual control in a narrower footprint. Root-guiding ribs direct roots downward to prevent circling, drainage holes in the ejectors support even moisture flow from bottom watering, and the plug ejector pushes the entire soil plug upward cleanly when it's time to transplant.

Growing Guide I've documented what I've learned while designing and using the Logical Grow Platform in a growing guide series on LogicalPlanet.com, covering everything from seeds through harvest. https://www.logicalplanet.com/collections/lgp/

How It Works

The Single Cell ThirdTray is built around three integrated components that work together through every stage of early plant growth.

Plug Cell — A single slim growing chamber that holds potting mix and seeds. Root-guiding ribs direct roots downward for strong, compact root systems and reduce circling before transplant.

Plug Ejector — A removable base insert that sits beneath the cell. When it's time to transplant, it pushes the entire soil plug upward for clean, damage-free removal. Drainage holes in the ejector prevent waterlogging while supporting even moisture flow from bottom watering.

Humidity Dome — A translucent lid that sits over the cell, trapping warmth and moisture to create an ideal microclimate for germination and early growth. Integrated micro-vents allow controlled airflow while maintaining high humidity when your seedlings need it most.

2-Stage Wicking System When used with the LGP Self-Watering Tray, the plug ejector sits above the water reservoir and wicks moisture upward through a 2-stage system. More wicking occurs at higher water levels, less as the reservoir drops — giving your plants consistent bottom moisture without waterlogging.

Key Features

• Slim single-cell format for herbs, greens, and narrow growing spaces
• 80mm deep cell for strong root development
• Root-guiding ribs direct roots downward and reduce circling
• Drainage holes in ejector support even moisture flow
• 2-stage wicking system for bottom watering integration
• Humidity dome with integrated micro-vents
• Plug ejector for clean, damage-free transplanting
• Fits one third of the LGP Self-Watering Tray
• Compatible with all LGP ThirdTray options
• Mix and match with other ThirdTrays in the same reservoir
• 100% printed, no supports required
• Use standalone or as part of the full LGP system

Dimensions Overall: 155mm × 70mm × 110mm (with dome) Cell depth: 80mm

Perfect For

• Herbs and greens that suit a narrower cell format
• Growers who want three distinct varieties in a single reservoir
• Mixed configurations alongside other LGP ThirdTrays
• Clean transplanting without disturbing root systems
• Standalone growing on a windowsill or under any grow light
• Integration with the LGP Self-Watering Tray for hands-off bottom watering

Printing Notes

These parts are forgiving and print successfully in most common materials.

• Prints support-free in provided orientations
• PLA or ASA recommended (see notes)
• 40% infill for general use, 100% for maximum longevity
• Use translucent material for the Humidity Dome for best results
• 0.4mm nozzle, 0.2mm layer height, 4 walls, Arachne wall generator

Notes: For long-term or outdoor use, ASA is recommended. PETG works well for indoor use. PLA at 40% infill is adequate for most indoor seed starting applications.

Print with Confidence I design and test my models carefully, but if you run into what appears to be a genuine design issue — a fit problem, a tolerance that doesn't work, or something that just doesn't behave the way the instructions suggest — let me know and I'll fix it. My goal is that every design I publish works as described. Email me at logicalplanet3d@gmail.com with details and I'll sort it out.

Note: I'm not able to account for every printer and material combination, so I recommend reviewing the print settings carefully before starting. Issues arising from incorrect settings or materials are outside the scope of this, but I'm still happy to help troubleshoot.

An Evolving System — Your Feedback Matters I've been growing in the LGP system for several months now, and that real-world experience has shaped almost every design decision in this release. It's been invaluable — and it's also shown me that no amount of bench testing replaces actually growing plants in a system over time.

I consider the LGP an evolving platform, not a finished product. If something works better a different way, or you discover something I haven't thought of, I genuinely want to hear about it. Your growing experience is part of what makes this system better for everyone. Reach out on Discord or email me at logicalplanet3d@gmail.com.

Related Links Logical Grow Platform (LGP) — Main Platform https://than.gs/m/1511734

LGP Self-Watering Tray https://than.gs/m/1540081

LGP 2×3 Cells XL HalfTray https://than.gs/m/1540074

LGP Single Cell HalfTray https://than.gs/m/1540075

Deep Cell Plug Tray – 3×5 Modular Seed Starter System https://than.gs/m/1511704

Deep Cell Plug Tray – 2×5 Modular Seed Starter System https://than.gs/m/1511705

Join the LogicalPlanet Discord https://linktr.ee/logicalplanet

Visit my blog for more details and other designs https://www.logicalplanet.com/

Revisions and Updates I occasionally update and revise my designs. When I do, I'll document the changes here. Check back periodically for the latest revision notes or if you're experiencing any issues with a model. Please email me at logicalplanet3d@gmail.com if you would like me to make a revision or have comments about this design.

2026-04-17: Initial release.