Starting Onions and Leeks Indoors for Almost Nothing

I bought onion starts last spring. Four dollars and change for a little rubber-banded bundle of sad-looking seedlings, and half of them melted within a week. If you’re going to throw money away, at least do it on something fun. Onions are not fun.

This year I started my own from seed in late January, and the whole setup cost me less than that bundle of failures. The plants are currently sitting under a shop light in my garage looking smug about it.

Why Onions and Leeks Need a Head Start

These two need a long time to bulk up. Leeks especially. We’re talking 100 to 120 days from transplant, and if you direct sow them in Redmond you’re basically hoping for a miracle. Starting indoors in January or February gives them the runway they need to actually be worth harvesting before October.

March is honestly a little late to start onions if you want big bulbs, but it’s not over. Leeks are more forgiving. Either way, get them going now if you haven’t.

The Actual Cheap Setup

You do not need a fancy seed starting rack. I know, because I almost bought one. It was $79.99 at the Home Depot on Aurora and I stood there holding the box for an embarrassing amount of time before putting it back.

Here’s what I actually use.

Container

A plastic salad clamshell from Costco. The big clear ones. I poke holes in the bottom with a skewer, fill it with seed starting mix, and close the lid for humidity. Free, basically, since we were eating the salad anyway. My daughters think this is disgusting. They’re not wrong but they’re also not in charge of the budget.

Growing Medium

I mix 2 parts coconut coir to 1 part perlite. That’s it. Holds moisture, drains well, doesn’t compact. A single coir brick runs about $2.89 at Bi-Mart and makes way more than you need for one tray.

Light

A $14.97 shop light from the hardware store, the 4-foot LED kind. I hang it about 3 inches above the seedlings. Onion seedlings are basically just tiny green threads and they will stretch toward anything that isn’t bright enough, so keep the light close. We’re talking 1500 lumens minimum for these guys to stay upright and not look like wet spaghetti.

I run it 14 hours on, 10 off with a cheap lamp timer. No, I do not trust myself to remember to turn it on every day. The timer cost $4.00 at the dollar store and has saved me from myself repeatedly.

Heat

Onion seeds germinate fine at 60 to 70 degrees. My garage sits around 55 at night in March, which is a little cool. So I just moved the tray inside on the kitchen counter until germination happened, about 7 days, then moved it back out under the light. No heat mat needed. This is the kind of frugal problem-solving that I’m unreasonably proud of.

Sowing the Seeds

Sprinkle the seeds pretty thickly across the surface, maybe a quarter inch apart, then cover with about an eighth inch of the coir mix. Onion seeds are tiny and annoying. I tried to sow them individually once and that was a bad 20 minutes of my life I’ll never get back.

For leeks, same deal. They can be transplanted and separated later without too much drama as long as you’re gentle. Think of it like untangling headphone cables except the headphones are alive and you care about them.

Water gently, close the clamshell lid, and wait. Once you see the little hooks poking up, pull the lid off and get them under the light immediately. Leggy onion seedlings are a real thing and they are deeply unimpressive.

What Comes Next

Once they’re a few inches tall and looking like actual plants, give them a haircut. Seriously, take scissors and trim them back to about 3 inches. It sounds wrong but it encourages thicker growth. I did not believe this the first time someone told me. I did it anyway. It works.

They’ll go out into the garden here in Redmond around late April, after our last frost window. Leeks can handle a light frost just fine. Onions less so, which is why hardening them off for a week or two matters. Which, now that I think about it, is basically just taking them outside to sit in the cold and feel bad for a while. Builds character.

Anyway. Skip the overpriced starts, raid your recycling bin, and get some onion seeds going. The whole thing costs about what you’d spend on that sad rubber-banded bundle. Except this time they’re yours from the start, and there’s a lot more of them.

You could say it’s a real onion of an investment. (I’m so sorry. I couldn’t help it.)

Photo by Simona Sergi on Unsplash