Planting Onions with Egg Carton Trays (The Simple Grid Method)

Planting onions sounds easy… until you realize spacing matters a lot. If onions are too close, you get tiny bulbs. Too far apart, you waste space. Measuring with a ruler works, sure—but it’s slow, and most people don’t stick with it.

That’s where the egg carton tray grid method becomes a game-changer.

With one simple tool you already have at home (an empty egg carton), you can:

mark perfect planting spots in seconds,
keep spacing consistent across the whole bed,
plant faster and more neatly,
and increase your chances of getting bigger, healthier onion bulbs.

This guide explains exactly how to do it step-by-step, plus the best spacing for different onion types, common mistakes, and pro tips to make this method work in raised beds, containers, or garden rows.

Why Spacing Matters for Onions
What You Need (Tools + Materials)
Step-by-Step: The Egg Carton Grid Method
Best Spacing for Onion Sets vs Seeds vs Seedlings
Soil Prep for Bigger Bulbs
Watering + Fertilizing Schedule (Simple and Effective)
Tips for Raised Beds and Containers
Common Mistakes (and Easy Fixes)
FAQs
Quick Summary Checklist

1) Why Spacing Matters for Onions

Onions grow underground, and the bulb needs room to expand. The plant can tolerate being closer than many vegetables, but crowding usually equals smaller bulbs.

Good spacing helps:

bulb size (more room = bigger onions)
airflow (less disease risk)
even watering (less competition)
easier weeding (you can actually reach between plants)

With the egg carton method, every onion starts with the same amount of space—so you get more consistent results across the whole bed.

2) What You Need

The basics

✅ Empty egg carton tray (paper/cardboard is best)
✅ Onion sets or onion seeds or seedlings
✅ Garden bed / raised bed / large container
✅ Compost or balanced garden soil
✅ Watering can or hose with gentle spray

Optional but helpful

Hand trowel
Rake
Mulch (straw, shredded leaves, or dried grass)
Organic fertilizer (or compost + a nitrogen source)

Which egg carton should you use?

Cardboard paper cartons are ideal—they press into soil better.
Plastic cartons can work, but they don’t “stamp” as cleanly.

3) Step-by-Step: The Egg Carton Grid Method (Simple & Fast)

Step 1: Prepare your planting area

Remove rocks, old roots, and weeds.
Loosen soil to about 15–20 cm deep.
Mix in compost (a generous layer is great).

Goal: Light, fluffy soil so onion bulbs can expand.

Step 2: Smooth and level the surface

Use your rake (or hands) to create a flat top layer.

This makes the carton stamp evenly.

Step 3: Press the egg carton tray into the soil

Place the egg carton on top of the soil and press down firmly with your hands.

You’ll get a perfect grid of small “cups” (planting dents).

Tip: If the soil is super dry, water lightly first. Slightly damp soil stamps better.

Step 4: Plant onions in each dent

If using onion sets (small bulbs)

Place one set in each dent, pointy side up.
Press gently so it stands.
Cover with soil so the tip is just barely under or slightly showing.

If using seeds

Drop 2–3 seeds per dent.
Cover lightly (about 0.5–1 cm).
Later, thin to the strongest seedling.

If using seedlings

Place seedling in the dent and firm soil around it.
Don’t bury the stem too deep.

Step 5: Water gently

Water slowly so you don’t wash seeds or sets out of place.

Step 6: Add mulch (optional but recommended)

A thin layer of mulch helps:

retain moisture,
reduce weeds,
keep soil cooler during hot days.

4) Best Spacing for Onion Sets vs Seeds vs Seedlings

Egg cartons naturally give you a spacing pattern—usually around 5–6 cm between centers (depends on carton type). That’s great for some onion goals, and for others you may want to skip holes.

Spacing guidelines (easy version)

Green onions / scallions: 5 cm spacing (egg carton spacing is perfect)
Medium bulb onions: 8–10 cm spacing (use every other dent)
Large bulb onions: 10–12 cm spacing (skip more dents or use a bigger grid)

How to adjust spacing using the carton:

Plant in every dent for green onions.
Plant in every other dent for larger bulbs.
Plant in one dent, skip two if you want extra-large bulbs.

5) Soil Prep for Bigger Bulbs (The Onion “Secret”)

Onions are heavy feeders early on, and they need:

Loose soil
Consistent moisture
Enough nitrogen early, then less later

Best soil mix

60–70% garden soil
20–30% compost
Optional: a small amount of sand or coco coir if soil is heavy clay

pH target (simple)

Onions generally like slightly acidic to neutral soil. If your soil is extremely acidic, growth can slow.

6) Watering + Fertilizing Schedule (Simple and Effective)

Watering

Keep soil evenly moist, not soggy.
If it dries out too much, bulbs can stay small or plants can stress.

A good rule:

Water when top 2–3 cm feels dry.

Fertilizing (easy routine)

Weeks 1–6: give onions nitrogen support (compost + light nitrogen fertilizer)
After bulb starts swelling: reduce nitrogen and let the plant focus on bulbing

Signs bulbs are forming:

The base of the plant begins thickening.
Leaves are strong and upright.

7) Tips for Raised Beds and Containers

Raised beds

This method is perfect because beds are flat and easy to stamp.

Best depth: at least 20–25 cm of soil.

Containers

You can still use the egg carton stamp method in wide pots or grow bags.

Container tips:

Bigger container = better bulb growth
Don’t overcrowd (skip dents for bulb onions)
Water more often (pots dry fast)

8) Common Mistakes (and Easy Fixes)

Mistake 1: Planting bulb onions too close

Result: lots of small bulbs.
✅ Fix: use every other dent or skip more.

Mistake 2: Soil too compact

Result: onions struggle to swell.
✅ Fix: loosen soil deeper + mix in compost.

Mistake 3: Too much nitrogen late in season

Result: huge leaves, tiny bulbs.
✅ Fix: reduce nitrogen when bulbing starts.

Mistake 4: Uneven watering

Result: split bulbs, stress, slow growth.
✅ Fix: consistent moisture + mulch.

Mistake 5: Not thinning seeds

Result: crowded onions.
✅ Fix: thin to 1 plant per dent.

FAQs

1) Can I plant onions directly in an egg carton?

You can start seedlings in cartons, but for this method we use the carton as a stamping tool (a grid marker).

2) Does this work for garlic too?

Yes—especially for spacing garlic cloves quickly. You may want bigger spacing though.

3) How deep should onion sets be planted?

About 2–3 cm deep, with the top just under or slightly showing.

4) Can I use a plastic egg carton?

Yes, but cardboard stamps better. Plastic can slip and won’t press as clearly.

5) Will onions grow if the spacing is small?

They’ll grow, but bulbs may be smaller. That spacing is perfect for scallions and small onions.

10) Quick Summary Checklist

✅ Loosen soil 15–20 cm
✅ Add compost
✅ Flatten top layer
✅ Press egg carton to stamp holes
✅ Plant sets/seeds/seedlings in dents
✅ Water gently
✅ Adjust spacing by skipping dents for bigger bulbs
✅ Feed early, reduce nitrogen later
✅ Keep moisture consistent

Conclusion

The egg carton tray grid method is one of the easiest gardening hacks for onions because it solves the biggest problem—spacing—in seconds. Whether you’re planting onion sets for full bulbs, seeds for a budget-friendly crop, or scallions for quick harvests, this method keeps your garden neat, efficient, and productive.

Planting Onions with Egg Carton Trays (The Simple Grid Method)