How to Grow Potatoes in Soil Bags

I spent my first three gardening seasons digging potatoes out of heavy clay soil, and I hated every minute of it.

Every harvest felt like an archaeological dig where one wrong slide of the spade sliced a perfect russet in half.

Then I tried fabric bags, and I haven’t planted a potato in the ground since.

It turns out that growing potatoes in bags isn’t just a space-saver for small yards. It’s actually a better way to grow them because the soil stays loose, drainage is automatic, and harvesting takes about ten seconds of tipping a bag over.

Here’s what actually works, from someone who got it wrong first.

Why I Switched to Growing Potatoes in Bags

The first summer I tried growing potatoes in the ground, I ended up with a lot of sore muscles and only a handful of tiny, dirt-caked tubers.

Our soil here is heavy, and potatoes need loose, airy ground to fill out properly. When the soil compacts, the potatoes stay small because they can’t push the heavy dirt aside.

Grow bags solved that problem overnight. The soil inside a fabric bag stays loose all season because no one ever steps on it.

Since the container walls are breathable, water drains out easily, which keeps the roots from sitting in cold mud. I also don’t have to worry about digging up my garden beds in the spring.

I just set the bags on the edge of the fieldstone path, fill them up, and let them grow.

That covers the basics. Here’s where most people mess up.

The Bag Size That Actually Works (And Why Fabric Rules)

I started with a cheap plastic grow bag from a discount store, and it was a mistake. The plastic trapped heat, making the soil too warm during July, and the drainage holes clogged with wet dirt.

Fabric grow bags are different because they allow air to reach the roots. When potato roots reach the edge of a fabric bag, they sense the dry air and stop growing outward.

This is called air-pruning, and it encourages the plant to grow a dense, fibrous root system rather than circling the pot. More roots mean more spots for potatoes to form.

For bag size, 15 gallons (57 liters) is the sweet spot.

A 5-gallon (19-liter) bag is too small. You’ll get plenty of leaves but only a couple of potatoes because the soil dries out too fast.

A 25-gallon (95-liter) bag works well, but it gets incredibly heavy. Once you fill a 25-gallon bag with wet soil and compost, you won’t be able to move it without hurting your back.

Stick to 15-gallon bags. They are light enough to drag around if you need to adjust their sun exposure, but large enough to hold three or four healthy potato plants.

I cover similar container setups in my guide on how to keep patio plants in pots thriving in full sun, which is worth a quick look if you’re planning a deck garden.

Preparing Your Seeds (And the Egg Carton Sprouting Trick)

Don’t use potatoes from the grocery store. Many grocery potatoes are treated with growth inhibitors to stop them from sprouting in the bin.

They can also carry latent diseases that will ruin your harvest. Instead, buy certified disease-free seed potatoes from a local garden center or online supplier.

I always sprout my seed potatoes before they go into the soil — trust me on this one. This process is called chitting, and it gives the plants a two-week head start.

I place the seed potatoes in an old cardboard egg carton, with the dimpled end — the side with the most eyes — pointing up.

Keep the carton in a cool, bright room out of direct sunlight for about two weeks. You’ll see stubby green or purple shoots start to push out of the eyes.

If your seed potatoes are small, like the size of a golf ball, plant them whole. If they are larger than a chicken egg, cut them into pieces.

Each piece needs at least two healthy sprouts.

Warning: Don’t plant freshly cut potatoes immediately. Let the cut pieces sit on a dry counter for 24–48 hours until the cut side forms a leathery skin. If you plant them raw, they’ll rot in the damp soil.

The Bottom Four Inches (Setting the Stage)

Potatoes are heavy feeders, so the soil mix needs to be rich but very light. I use a mix of 60% high-quality potting soil and 40% organic compost.

Potting soil keeps the mix loose so water can drain, while compost provides the steady nutrients the tubers need to grow.

Some gardeners like to add a handful of old coffee grounds to the mix to slightly lower the pH, which can help prevent potato scab.

If you’re curious about that, check out 7 plants that love coffee grounds for a breakdown of which crops benefit most.

To plant, first roll down the sides of your grow bag like a cuff. This makes it easier to reach the bottom and ensures the high fabric walls don’t block the light when the plants are small.

Fill the bottom of the bag with 4 inches (10 cm) of your soil mix.

Place three or four seed potato pieces on top of the soil, spacing them evenly apart. Make sure the sprouts are pointing upward.

Cover them with another 3 inches (8 cm) of soil mix, and water them gently until the soil is damp but not muddy.

The Piling Game: Hilling Up as They Grow

Once the green shoots reach about 8 inches (20 cm) tall, it’s time to start hilling.

Hilling means adding more soil around the stems of the plants. As you cover the lower stems, the plant grows new roots from those buried sections.

These new roots produce the potatoes, so hilling directly increases your harvest.

To hill, carefully unroll the fabric cuff of the bag a few inches. Add more soil mix around the stems, leaving just the top 2–3 inches (5–8 cm) of green leaves exposed.

Don’t bury the leaves completely, or you’ll slow down the plant’s growth.

Repeat this process every time the stems grow another 8 inches (20 cm), unrolling the bag as you go, until the soil is about 2 inches (5 cm) from the top rim.

I find using compost for the final layers works best because it gives the shallow roots a nutrient boost late in the season.

If you don’t have enough compost on hand, you can learn the basics in my article on how to trench compost to see how I build up my soil supply.

Watering Without Rotting the Tubers

Watering is the hardest part of growing potatoes in bags.

Fabric bags dry out much faster than garden beds because the air pulls moisture through the sides. During hot summer weeks, you might need to water every day.

But you can’t just pour water on top and assume it’s fine.

If the soil gets dry, it pulls away from the fabric sides, and the water will just run down the gaps and out the bottom without soaking the roots.

I always stick my finger 2 inches (5 cm) into the soil before watering. If it feels dry at that depth, water slowly until it runs out of the bag’s bottom seam.

According to the Oregon State University Extension, consistent moisture is critical during the flowering stage because that’s when the plant starts forming the tubers.

If the plants dry out now, you’ll get small, misshapen potatoes.

On the other hand, don’t let the bag sit in a puddle. Too much water will cause the potatoes to rot in the bag.

The Best Part: Tipping the Bag Over

After the plants flower, the green vines will slowly start to turn yellow and die back.

This is completely normal and means the plant is sending its final energy down to the potatoes.

Once the vines are dry and brown, stop watering and wait a week. This waiting period allows the potato skins to cure and toughen up, which helps them last longer in storage.

When you’re ready to harvest, lay out a large canvas tarp on the lawn.

Pick up the grow bag by the handles, tip it sideways, and dump the soil onto the tarp.

You can sift through the loose dirt with your hands and pull out clean, unbruised potatoes.

No shovels, no sliced tubers, no sore back.

Just a pile of fresh potatoes ready for the kitchen.

— Anh