Grow Onions Vertically and Save Space—Soil Beds Are Outdated!

Whether you’re working with a balcony railing, a backyard fence, or a sunny wall, this low-cost and space-saving approach allows you to enjoy a regular supply of onions for cooking—without the need for a patch of ground.

Why Grow Onions Vertically?

There are several benefits to growing onions in vertical bottle planters:

• • Space Efficiency: Perfect for tight spaces like balconies or patios.

  • Sustainability: Reuses plastic bottles that would otherwise become waste.

  • Accessibility: Easy to maintain and harvest without kneeling or bending.

  • Air Circulation: Vertical gardens improve airflow, reducing the risk of rot and disease.

This method works best for green onions (scallions) or small bulb onions, though even larger varieties can be grown with a little extra care.

What You’ll Need

• • 1.5 to 2-liter plastic bottles (cleaned and labels removed)

  • Onion sets or green onion bulbs

  • Potting soil (well-draining)

• • Compost or worm castings

  • A drill, utility knife, or scissors

  • Zip ties, wire, or sturdy string

  • A sunny wall, fence, or railing

Prepare Your Bottles

1. 1. Create Openings: Cut a large horizontal window along one side of the bottle (about 10×5 cm) to serve as the planting area. Leave a strong border around the cut for stability.

       

   2. Add Drainage Holes: Drill or poke several small holes in the bottom of the bottle to allow excess water to drain.

   3. Make Hanging Holes: On the upper sides of the bottle, create two small holes to run wire or string through for hanging.

   4. Optional Stack Drainage: If stacking vertically, drill a small hole in the cap to allow water to trickle down to the bottle below.

Choose Your Onion Type

• • Green Onions/Scallions: These are ideal for vertical planting. They grow quickly and don’t require large space for bulb development.

  • Mini or Bulb Onions: Choose short-day or intermediate varieties if growing in mild climates. These may produce small bulbs in vertical containers.

Avoid using large mature onions as starter bulbs. Instead, go for small sets or trimmed-off root bases from kitchen scraps, which regrow well.

Potting Mix and Planting

Fill each bottle with a light, nutrient-rich mix. A blend of potting soil and compost or worm castings provides a good base.

To Plant:

• • Insert one onion set or green onion base into the soil with the roots downward and the green tip facing up.

     

  • Push it just deep enough so the top is level with the soil surface.

  • Plant only one per bottle opening to ensure enough room for root expansion and airflow.

Water thoroughly after planting, allowing excess water to drain.

Wall Garden Setup

Use wire, zip ties, or string to attach the bottles securely to a wall or fence. Space them about 20–30 cm apart vertically so each plant has room to grow.

Ensure the wall gets at least 5 to 6 hours of direct sunlight daily. If indoors, place near a bright window or under grow lights.

Care and Maintenance

• • Watering: Keep the soil evenly moist, but not soggy. Water 1–2 times per week or when the top layer feels dry.

  • Fertilizing: Use diluted compost tea or organic liquid fertilizer every 3–4 weeks for healthy growth.

  • Trimming: If growing green onions, harvest the green tops regularly to encourage new growth.

If growing for bulbs, avoid harvesting the green tops too often, as this may reduce bulb size.

Harvesting Your Onions

For green onions, you can start harvesting the leafy tops once they’re about 15–20 cm tall. Use kitchen scissors to snip the greens, leaving at least 2–3 cm of growth to allow regrowth.

If growing bulb onions:

• • Harvest when the leaves turn yellow and start to flop over.

  • Stop watering for 7–10 days to let the bulbs mature and dry slightly.

  • Gently pull out the onions and allow them to cure in a dry, shaded area for about 1–2 weeks before storing.

Replanting and Expanding

After harvesting, you can refresh the soil and replant new onion sets in the same bottles. Crop rotation isn’t a major issue in container setups, but refreshing the potting mix and adding compost can improve yields.

Want more? Add additional rows of bottles to your wall or try mixing in other leafy crops like spinach or lettuce to create a mini vertical kitchen garden.

Final Thoughts

Growing onions in a wall garden using recycled plastic bottles is a practical, eco-friendly gardening solution for those with limited space. It allows you to enjoy fresh green onions or small bulb onions year-round without a traditional soil bed. Whether you’re a beginner or seasoned gardener, this method is easy to start and maintain—and offers a rewarding harvest right at your fingertips.