Using paper egg carton flats as a planting \u201cgrid\u201d is a slick way to space onion sets evenly, keep weeds down, and get a tidy bed like the one in your photos. The cartons act like a biodegradable mulch and spacer\u2014then break down as the onions grow.<\/p>\n
Below is everything you need to do it successfully, without extra fluff.<\/p>\n
What this method is best for<\/p>\n
Onion sets (small dormant bulbs) for full-size onions
\nScallions\/green onions (you can plant closer or harvest early)
\nSmall garden beds where neat spacing and weed control matter
\nSkip this method for plastic\/foam cartons. Use only plain paper\/pulp cartons that tear easily.<\/p>\n
Materials<\/p>\n
Paper egg carton flats (the 30-egg \u201ctrays\u201d are perfect, but regular 12\/18 work too)
\nOnion sets (or small transplants)
\nCompost (or aged manure) + basic garden soil
\nRake\/hoe\/shovel
\nWatering can or hose with gentle spray
\nOptional: balanced fertilizer or a nitrogen-forward fertilizer for early growth
\nOptional: mulch (straw\/leaves\/grass clippings) for bed edges
\nStep 1: Choose the right onion type (quick but important)<\/p>\n
Onions form bulbs based on day length. If you buy locally, you\u2019re usually fine\u2014but if ordering online:<\/p>\n
Long-day onions: best for northern areas (roughly above 36\u201338\u00b0 latitude)
\nShort-day onions: best for southern areas
\nDay-neutral: flexible, good \u201csafe choice\u201d for many places
\nAlso: smaller sets are better for bulbing onions. Very large sets tend to bolt (send up flower stalks) and make smaller bulbs.<\/p>\n
Step 2: Timing (when to plant)<\/p>\n
Cold-winter climates: plant sets early spring, as soon as soil can be worked (often 2\u20134 weeks before last frost).
\nMild-winter climates: short-day onions are often planted fall to winter for spring harvest.
\nOnions like cool starts and steady growth. Heat later is fine\u2014especially once bulbs begin forming.<\/p>\n
Step 3: Prep the bed (this matters more than the cartons)<\/p>\n
Onions want loose soil and good drainage.<\/p>\n
Clear grass\/weeds from the strip (a trench along a fence line is totally fine).
\nLoosen soil 6\u20138 inches deep.
\nMix in 1\u20132 inches of compost.
\nLevel the surface so the trays sit flat.
\nAvoid heavy, soggy soil. If water puddles there after rain, raise the bed a bit or add more compost.<\/p>\n
Step 4: Prep the egg carton trays<\/p>\n
Use paper\/pulp trays only (no shiny coatings if possible).
\nIf they\u2019re stiff, lightly wet them so they mold to the ground.
\nLay flats end-to-end where you want the row.<\/p>\n
Optional but helpful<\/p>\n
Tear or poke a few extra holes in the bottoms to help roots punch through faster.
\nIf wind is an issue, sprinkle a little soil on the trays to hold them down before placing sets.
\nStep 5: Place onion sets in the cups<\/p>\n
Put one onion set per cup, pointy end up.<\/p>\n
Spacing rules (use the trays to your advantage)<\/p>\n
Full-size onions: aim for 4\u20136 inches between plants
\nWith egg trays, that often means planting every other cup (or choosing a tray style with wider spacing).
\nScallions \/ smaller bulbs: 2\u20133 inches is fine (plant more cups).
\nIf you plant every cup in a tight tray, you\u2019ll get lots of greens and smaller bulbs unless you thin\/harvest some early.<\/p>\n
Step 6: Cover correctly (depth makes or breaks onions)<\/p>\n
This is the #1 mistake people make.<\/p>\n
Cover sets with about \u00bd to 1 inch of soil
\nYou should still be able to feel the set isn\u2019t buried deep
\nDon\u2019t mound heavy soil over them
\nOnions like to \u201csit up\u201d a bit as they bulb. Planting too deep encourages rot and slows bulbing.<\/p>\n
How to do it cleanly:<\/p>\n
Toss a thin layer of soil over the trays and sets (like in your photos), then gently rake or pat so the soil fills the gaps without packing hard.<\/p>\n
Step 7: Watering (steady, not soggy)<\/p>\n
Right after planting: water thoroughly to settle soil.<\/p>\n
After that:<\/p>\n
Aim for about 1 inch of water per week (rain + watering)
\nKeep moisture consistent, especially during leaf growth
\nReduce watering a bit once bulbs are close to harvest and tops start falling
\nIf the bed stays wet for long periods, onions can rot\u2014better to water deeply but less often than to sprinkle daily.<\/p>\n","protected":false},"excerpt":{"rendered":"
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