📄 Green Onion Grower

Green Onion Grower


The Green Onion Grower is a simple countertop system for continuous regrowth of store-bought or garden-fresh green onions. Designed to fit a wide-mouth mason jar, it holds stems securely above the water while roots grow freely below. With regular water changes and a small dose of Seeded nutrients, you can enjoy crisp, green shoots that regrow again and again.

What You’ll Need

  • Green Onion Grower (3D-printed PLA top)
  • Wide-mouth mason jar (pint or quart size)
  • Tap or filtered water
  • Fresh green onions from the store
  • Nutrient packet 

Preparing Your Green Onions

  1.  Start with fresh onions
    1. Choose bunches with healthy white bases and visible roots.
    2. Avoid onions with dried or mushy ends.
  3.  Make your first cut
    1. Lay the onions on a clean surface.
    2. Cut the green tops off, leaving 2–3 inches of the white base with roots attached.
    3. Use the cut greens for cooking, the bases will be used for regrowth.
  5. Rinse and trim
    1. Rinse the bases gently to remove any soil.
    2. If roots are long and tangled, trim them to about ½ inch for easier placement.

Setup Instructions

  1. Prepare the nutrient solution
    1. Prepare the nutrient mix following the instructions on the packet.
    2. Fill jar to the bottom of the main opening. The goal is to keep the roots submerged but the rest of the onion dry.
  3. Place the grower top
    1. Set the Green Onion Grower securely on the mason jar. It should sit level and snug. The band of the mason jar should be able to fit over the lid to secure it.
  5. Insert your onions
    1. Slide each onion base into an opening so the roots are submerged and the white stem rests above the top.
  7. Find the right spot
    1. Keep your grower in bright, indirect sunlight such as a kitchen window or bright countertop.

Growing & Harvesting

  • Daily care: Keep the water level high enough to cover the roots. Top off as needed every 2–3 days.
  • Weekly refresh: Replace the water and nutrients once per week to maintain freshness and prevent buildup of algae. See note below on using hydrogen peroxide to sanitize without harming the onions.

Harvesting:

  • Cut the green tops when they reach 6–8 inches tall.
  • For faster regrowth, cut higher—leave at least 2 inches of green stalk above the white base.
  • Each base can regrow multiple times before needing replacement.

Cleaning & Maintenance

  • Every 1–2 weeks, remove the grower top and rinse both the jar and top with mild soap and water.
  • Avoid abrasive scrubbers—use a soft cloth or sponge.
  • Rinse thoroughly before refilling with fresh nutrient water.
  • To sanitize the system, utilize a 1 to 1 mix of water and 3% hydrogen peroxide. After sanitizing add the nutrients.

Troubleshooting

Issue, Likely Cause, Solution

  • Slimy or brown roots
    • Water left unchanged too long
    • Empty and clean the jar, then refill with fresh nutrient mix
  • Pale or thin shoots
    • Low light or depleted nutrients
    • Move to brighter light and refresh nutrients
  • Mold or odor
    • Poor airflow or residue buildup
    • Rinse thoroughly and dry before refilling

Pro Tips

  • Rotate the jar every few days for even light exposure.
  • Harvest often to encourage new growth.
  • Replace bases once growth slows or roots begin to break down.

Safety & Disposal

  • The grower is printed from PLA, a plant-based plastic safe for indoor growing.
  • Avoid high heat above 120°F (49°C).
  • Dispose through recycling or composting services where available.