If you're gearing up for Walla Walla onions planting, you're probably already dreaming about those massive, sweet slices on a backyard burger. These onions are legendary, especially here in the Pacific Northwest, but honestly, anyone with the right timing and a bit of dirt can grow them. They aren't your typical pungent, tear-inducing onions; they're mild, juicy, and big enough to cover a whole sandwich with just one slice.
However, they can be a little bit finicky if you don't know their quirks. Unlike the rock-hard onions you find in the supermarket bins in December, Walla Wallas are "sweet" onions, which means they have a higher water and sugar content. This also means they have a shorter shelf life and a specific growing window. If you want to get those jumbo-sized bulbs, you've got to play by their rules.
When is the Best Time to Start?
Timing is arguably the most important part of the whole process. Because Walla Wallas are technically a "long-day" or "intermediate-day" variety, they react to the amount of sunlight they get. In their home territory of Washington state, the traditional method is actually fall planting. You get them in the ground around late August or September, let them get established before the frost, and then they overwinter and explode with growth as soon as the ground warms up in the spring.
If you live in a place with brutal, soul-crushing winters where the ground turns into a solid block of ice for four months, fall planting might be a gamble. In those cases, you'll want to go for a very early spring planting. As soon as the soil can be worked—meaning you can stick a trowel in it without it snapping—you get those onions in. They can handle a light frost, so don't be too scared of a little cold snap.
Getting Your Soil Ready for Success
Let's talk about dirt for a second. Onions are heavy feeders. They aren't the kind of plant you can just toss into a neglected corner of the yard and expect results. For Walla Walla onions planting, you want soil that is loose, crumbly, and absolutely loaded with organic matter.
I usually spend a week or two prepping the bed before I even think about touching the seedlings. Mix in a healthy amount of well-rotted compost or aged manure. Onions need nitrogen to grow those big green tops, and since every leaf on the top represents a ring in the bulb, you want as many big, healthy leaves as possible.
One thing people often forget is drainage. Onions hate sitting in soggy "wet feet" soil. If your ground is heavy clay, you're better off building a raised bed. It'll save you a lot of heartache and prevent the bulbs from rotting before they even have a chance to get big.
Seeds, Starts, or Sets?
You've got three main ways to go about this, and everyone has their favorite.
- Seeds: This is the cheapest way, but it takes the most patience. If you're doing a spring planting, you'll need to start these indoors about 10-12 weeks before your last frost. They look like tiny blades of grass for a long time, and it can be a bit nerve-wracking.
- Sets: These are those tiny little onion bulbs you see in mesh bags at the hardware store. While they're easy to poke into the ground, a lot of gardeners find that they bolt (go to seed) more easily than other methods.
- Starts (Transplants): These are my personal favorite. They look like little bunches of green onions or scallions. They've already got a head start, they're usually more resilient than seeds, and they tend to produce the biggest bulbs.
Whichever way you go, just make sure you're getting actual Walla Walla variety. There are other sweet onions out there, like Vidalias, but they are "short-day" onions and won't bulb up correctly if you live too far north.
The Nitty-Gritty of Putting Them in the Ground
When you finally get to the actual Walla Walla onions planting day, don't overthink it, but do pay attention to the depth. A big mistake people make is burying them way too deep. You only want to put the roots and maybe an inch of the white base into the soil. If you bury them like a tulip bulb, the onion will struggle to expand, and you'll end up with something that looks more like a weird leek than a round onion.
Space them out about 4 to 6 inches apart. I know they look tiny now, but remember, these things can get as big as a softball. If they're crowded, they'll compete for nutrients and you'll get a bunch of "golf balls" instead of "softballs." If you have extra starts, you can plant them closer—say 2 inches apart—and then pull every other one as a "green onion" to eat while they're growing. It's a great way to thin the crop and get an early harvest.
Keeping Your Onions Happy All Season
Once they're in the ground, the real work is mostly just staying out of their way while providing two things: water and weed control.
Onions have very shallow roots. They aren't like tomatoes that will send roots deep into the earth to find water. If the top two inches of soil are bone dry, your onions are stressed. You want consistent moisture. A light mulch of straw or dried grass clippings can really help keep the moisture in and—more importantly—keep the weeds down.
Speaking of weeds, you have to be ruthless. Because onion leaves are just vertical spikes, they don't provide much shade to the ground. This means weeds will sprout everywhere around them. If you let the weeds take over, they will steal all the nitrogen you worked so hard to put in the soil. Just be careful when you're hoeing or pulling weeds; since onion roots are so shallow, you don't want to accidentally yank the onion out or damage the bulb with a sharp tool.
The Mid-Season Growth Spurt
About halfway through the growing season, you might want to give them a little "side-dressing" of fertilizer. A high-nitrogen organic fertilizer sprinkled along the row can give them that extra push they need to start bulbing.
Keep an eye on the weather, too. If you get a random heatwave, they might need water every single day. If they start to look a bit yellow, check your soil moisture. Usually, yellowing leaves mean either they're thirsty or the soil has run out of gas (nutrients).
When to Harvest and How to Use Them
You'll know it's time to harvest when the onion tops start to flop over. It looks a bit sad, like your garden just gave up, but it's actually the plant's way of saying it's done growing. Once about half the tops have fallen over, you can go ahead and stop watering. Let them sit in the dry ground for a few days, then gently lift them out.
Don't leave them in the sun for too long once they're pulled, as they can actually get sunburned. Move them to a shady, breezy spot to "cure" for a few days.
Now, here's the kicker with Walla Wallas: don't expect to store these in your pantry until Christmas. Because they have so much sugar and water, they don't cure like storage onions. They'll usually stay good for about a month or two, maybe a bit longer if you keep them in a cool, dark, well-ventilated place. But honestly, they're so delicious that they rarely last that long anyway.
Slice them raw for salads, grill them in thick rounds, or caramelize them for the best French onion soup you've ever had. Once you've experienced the payoff of Walla Walla onions planting, you'll probably find yourself making room for them in your garden every single year. It's a bit of work, sure, but that first bite of a sweet, home-grown onion makes every minute of weeding totally worth it.