Can you grow onions and potatoes together? The answer is a resounding yes!
Onions and potatoes are perfect companion plants who grow together happily.
To avoid some common planting mistakes and grow a successful crop, check through this onion and potato companion planting guide.
Can You Grow Onions And Potatoes Together?
Growing certain vegetables together (or keeping them apart) is called companion planting. As you’re no doubt aware, some vegetables grow really well together (good companions) while others are terrible neighbors (bad companions).
Luckily, you can grow onions and potatoes together. Neither plant upsets the other, they don’t compete for the same root zone, and they enjoy growing in similar soil.
Potatoes grow deeper in the soil than shallow rooted onions, which grow almost on the surface. Because they grow at different depths, their roots aren’t competing for the same nutrients. That’s one reason potatoes and onions make good companions.
Another reason is that they both thrive in free draining soil with a soil pH of 6.0 to 6.8. The ideal pH range for potatoes is 6.0 to 6.5, and for onions it’s 6.0 to 6.8. Don’t worry about the slight difference, they’re close enough that it doesn’t matter.
Potatoes and onions are both hungry for nitrogen too, and growing crops with similar needs together, makes fertilizing easy.
Are There Any Benefits From Growing Onions And Potatoes Together?
Actually there are!
When onions are grown next to potatoes, they can help to deter aphids and white fly.
By growing onions and potatoes together, your potatoes will benefit from the natural pest repellent properties of onions.
Natural pest control methods are essential for organic growers, and even if organic growing seems a bit too hit-or-miss for your tastes, I’m sure you’ll agree that anything that cuts down on the need for costly pesticides is a bonus.
Onions and potatoes also share a harvest window, so there’s no need to worry about root disturbance when it’s time to harvest the bed.
Another benefit of growing onions and potatoes together is efficient use of space, particularly if you’re growing in raised beds.
Because onions don’t have enormous, bushy top growth, they’re perfect for planting along the edge of a raised bed when potato plants are the main crop.
How Much Space Between Onion And Potato Rows?
When you’re new to growing vegetables, it’s often hard to picture how big the mature plants are going to grow.
When we plant seedlings, small transplants, or sow seed, the small size of all of these youngsters can deceive us into thinking we don’t need to be as generous with our plant spacing as we should be.
A vegetable garden in early spring looks pretty deserted and unless you keep in mind the mature plants that will be flourishing in those beds in a few months, you could plant your crops too close together.
Look at this photo of some young potato plants. Doesn’t it look like you could squeeze a row of onions into the space between the potato rows?
Now look at this photo. See how the space is gone now the potato plants are bigger?
If onions were in that gap, they would have been smothered long ago.
Always check the mature height and spread of the crops you grow so you can get your spacing right.
For potatoes the recommended spacing between rows is 24 – 36 inches (60 cm – 90 cm).
But you won’t need to leave that much room between a row of potatoes and a row of onions because the leaf spread on the onion tops is much less than the potatoes.
Onion rows are typically planted 12″ – 15″ apart (30 cm – 38 cm).
From those measurements we can work out how much space we need to leave between our potato plants and our row of onions.
If we say our mature potato plants have a spread of 24 inches (60 cm), that’s 12 inches (30 cm) either side from the seed tuber planted in the center of the row.
Onions only need 6 inches (15 cm) either side of the onion set or transplant.
Add the two together and we get 18 inches (46 cm).
Plant your row of onions 18 inches (46 cm) from the center of your row of potatoes, and the potatoes and onions will both have room to spread.
Don’t forget to leave yourself some room to get among your plants to mulch, weed, and water if you’re planting in a traditional row garden.
Plant Onions Where They Won’t Be Shaded by The Taller Potato Plants
As well as leaving enough space between rows of potato and onion plants, make sure you grow onions on the southern side of the potato plants (in the northern hemisphere).
Potato plants grow taller then onions. If you plant onions on the north side of potatoes, the potatoes will shade them. And onions need full sunlight to make big bulbs.
Be Careful When You Hill Your Potatoes
Potatoes need hilling as they grow to prevent greening in tubers growing close to the surface. As you hill the potatoes you also eliminate weeds.
To hill potatoes, you use a hoe to pull soil from between the rows and heap it around the stems of the potato plants.
When you’ve got onions growing close to your potatoes, you need to be careful when you hill so you don’t disturb the shallow rooted onions.
Don’t take soil from the space between the potato and onion row; if you do, use a light touch.
A good alternative to hilling with soil, is adding a thick straw mulch.
Can You Grow Green Onions And Potatoes Together?
You sure can.
Green onions, scallions, Welsh onions, bunching onions, and spring onions are ready for harvest much earlier than main crop bulb onions, and because they’re shallow rooted, there’s no risk of disturbing the potato plants when you harvest them.
There’s something you need to know about green onions, though. Depending on where you’re from, you’ll call the slender non-bulbing onions by one of the above names, but they’re not all the same.
Green onions (Allium cepa) are simply regular bulbing onions harvested early. If you left them to grow, they would reach their mature size and form bulbs. Any kind of bulbing onion can be grown and harvested early as a green onion.
In the UK, green onions are called spring onions when they’re harvested young before the bulbs form.
Welsh onions and bunching onions (Allium fistulosum) are a different type of onion altogether. These onions grow as a clump, and they can even be grown as perennials in growing zones 6 to 9.
Perennial vegetables are crops that come back year after year, unlike annuals which need to be planted each year.
With Welsh onions, the leaves are the crop, and you harvest them by cutting what you need. The leaves regrow to give you a harvest 2 or 3 times a year, and they’ll stand over winter providing some very welcome fresh greens at that time of year.
Scallions are similar to Welsh onions but they produce thicker stems. You harvest scallions by digging up the clump, taking what you need, then replanting the rest.
Both plants can be dug up, divided, and replanted, giving you more clumps as time goes on.
The difference between these types of onions is something you should keep in mind when you grow “green onions” next to potatoes.
My advice is to grow green onions and spring onions with potatoes, but set Welsh onions and scallions where they won’t be disturbed when you dig up the potatoes in the neighboring row (unless you plan to divide the clumps and replant).
Again, make sure the potato plants won’t block the light from the green onions. Plant the clumps of onions on the south side of the potatoes.
What Else Can You Grow With Potatoes?
As with onions, the best companions to grow alongside potatoes are shallow rooted vegetables.
Try growing kale, cabbage, collard greens, cauliflower, broccoli, spinach, bush beans, pole beans, fava beans (broad beans) corn, chives, horseradish, leeks, cilantro (coriander) and lettuce.
One idea is to grow climbing peas at the back of your growing bed, plant a row of potatoes in the middle, and grow a row of onions at the front.
Keep These Plants Away from Potatoes
Bad companions for potatoes include vegetables from the nightshade or solanaceous family.
Potatoes, eggplant, tomatoes, and peppers are all members of the nightshade family, and that means they’re all susceptible to the same diseases, like blight and mosaic viruses.
Keeping some distance between these plants helps stop diseases sweeping through your crops as easily.
It’s also sensible to keep vining plants like summer and winter squash, and cucumbers, away from potatoes. The vines from these plants spread a long way and they’ll soon weave their way through your potato plants, making it impossible for you to harvest any potatoes without destroying the squash.
Non-vining squash varieties do exist, but even then, the plants will compete with your potatoes for nutrients and water, and their huge leaves can spread over neighboring rows and block essential light.
Root vegetables like carrots, parsnip, beets, and turnips are bad potato companions for a couple of reasons.
Number one: they grow down at the same depth as potatoes which means their roots will compete for nutrients and water, if they’re grown close to a row of potatoes.
Number two: when you harvest potatoes, you’ll disturb root veggies growing nearby, and vice versa.
That’s A Wrap, Let’s Recap!
Question: Can you grow onions and potatoes together?
Answer: yes, potatoes and onions make great growing companions, thanks to their similar soil requirements and different root zones.
Onions can help to ward off some insect pests too, which is always a big bonus in the vegetable garden.
Make sure you leave enough space between your onions and potatoes so the potato canopy doesn’t grow over your onions and smother them, and where possible, plant your onions in front of the potatoes where they’ll get plenty of sunshine.
Thanks for reading: Can you grow onions and potatoes together? Good luck with your garden!