Growing Potatoes in Bags: A Practical Guide

Which bag should you use?

Three types of container work well: fabric grow bags, repurposed plastic sacks (compost bags with holes cut in the bottom are a classic option), and large buckets or pots. All three can produce a decent harvest, but they behave differently.

Fabric grow bags breathe and drain well, which lowers the risk of rot if you overwater by accident. The downside is that they dry out faster in full sun, especially on a hot patio. Plastic sacks hold moisture longer but need extra drainage holes cut into the base yourself — skip that step and the soil turns waterlogged and starved of oxygen fast.

Size matters more than material. An undersized bag simply limits how many tubers the plant can form, because potatoes only develop in the soil volume they actually have access to. Budget at least 8 gallons (roughly 30 litres) for a single plant, and closer to 10 gallons if you're planting several seed potatoes in one bag.

Good to know. Dark bags heat up faster in direct sun than light-coloured ones, which can dry the soil out quickly on a hot day. If your bag will sit on a sunny, paved patio, a natural fibre or light-coloured bag is often a better choice than black plastic.

Many purpose-made potato grow bags include a small flap or window near the base. It lets you feel for new potatoes without unrolling the whole bag, which is handy if you want to harvest a few at a time through the summer. Without one, you can still check by feeling carefully down the side of the bag.

Second-hand containers work just as well as anything bought specifically for potatoes. Old compost sacks, feed bags, or sturdy reusable shopping totes will all get you through a season or two. What actually matters is that the material holds up to repeated wetting without rotting through, that you've cut enough drainage holes, and that the bag stands upright without tipping once it's full of damp soil.

How much soil and how many seed potatoes per bag?

More seed potatoes means more plants, but only if there's enough soil volume for all of them to form tubers properly. Crowd the bag and the plants compete for water and nutrients, giving you a larger number of noticeably smaller potatoes.

The soil doesn't need to be a specialty mix, but it should be loose, well-draining, and ideally blended with some compost or well-rotted manure. Heavy, compacted soil holds too much water at the bottom of the bag and increases the risk of waterlogged roots. If you want a clearer picture of what different soil types actually do, our guide to garden soil types covers the differences between potting mix, compost and ordinary garden soil.

A reliable starting mix is two parts multipurpose or potting soil to one part well-rotted compost or manure. If you know your soil tends to compact when wet, mixing in a handful of perlite per bag improves drainage further. Avoid pure peat-based mixes on their own — once they dry out completely, which happens easily in a bag on a hot, forgotten weekend, they can be surprisingly hard to re-wet evenly.

Chit the seed potatoes before planting

Chitting means letting seed potatoes sprout short, sturdy shoots before they go into the soil. It gives the plant a head start and can shave a week or two off the time to harvest — a real advantage in a bag, where the growing window often feels tighter than it does in open ground.

Set the seed potatoes somewhere cool and bright, ideally around 8–15°C (46–59°F), for four to six weeks before planting. Too warm or too dark and the shoots grow long, thin and fragile instead of short and strong. For the full step-by-step process, see our guide to chitting potatoes.

A bright windowsill out of direct sun, an unheated porch, or a cool but frost-free shed with a window all work well. Arrange the seed potatoes eyes-up in an egg carton or shallow tray — it keeps them easy to handle without snapping the shoots when it's time to plant. Aim for shoots around 1–2 cm (roughly half an inch) long, short and green rather than long and pale, before you put them in the bag.

How to plant potatoes in a bag

1. Fill the bottom of the bag with 12–15 cm (5–6 in) of soil. If your bag has a rollable rim, keep it rolled down for now — it makes hilling later much easier.
2. Set the seed potatoes eyes-up. Space 3–4 chitted potatoes evenly across the bag, following the table above for your bag size.
3. Cover with 10–12 cm (4–5 in) of soil. Don't pack it down hard — the shoots need loose soil to push through easily.
4. Water thoroughly. The soil should be moist all the way through, not just damp on top.
5. Place the bag in full sun, sheltered from wind. Potatoes need at least six hours of direct sun for a decent harvest.

If you're setting up several bags, grouping them close together works well — almost like a small raised bed. It makes watering faster and reduces how much the wind dries the soil out from the sides. Leave a little space between bags even so, enough to hill up and harvest each one without climbing over the others.

Hilling: adding soil as the plant grows

Hilling means adding more soil around the stem as the plant grows. It's the single most important thing you can do for potatoes in a bag, for two reasons: it encourages the plant to form more tubers along the buried stem, and it keeps developing tubers shielded from daylight.

Once the plant reaches 15–20 cm (6–8 in) tall, add another 8–10 cm (3–4 in) of soil, leaving only the top third of the foliage exposed. Repeat every time the plant catches up, until the bag is full or the plant starts flowering. If you kept the bag's rim rolled down at planting, unroll it gradually as you add soil.

The reason hilling increases yield is that new tubers only form along the section of stem buried in dark, moist soil. The more stem you bury, the more nodes get the chance to set tubers. It's the same principle that applies to potatoes grown in open ground, but a bag makes it easier to do properly since you can reach all the way around the plant.

Common mistake. Tubers exposed to light turn green and develop solanine, a compound that's toxic and bitter-tasting. Green potatoes shouldn't be eaten. Keep an eye out for any tuber poking through the surface and cover it straight away if you spot one.

Good to know. If your bag sits somewhere you don't visit daily — a holiday cottage or a balcony you rarely check — a simple drip irrigation kit on a timer can make a real difference. It keeps the soil evenly moist without relying on memory, which is exactly the kind of consistency bag-grown potatoes respond to best.

Watering and feeding potatoes in bags

A bag holds less soil than a raised bed and drains faster, which means it dries out noticeably quicker — especially fabric or breathable bags. Expect to water bagged potatoes more often than potatoes in the ground, often every other day in hot, sunny weather.

Check by pushing a finger a couple of centimetres into the soil. If it feels dry there, it's time to water. Never let the bag dry out completely while tubers are forming — it produces small, misshapen potatoes and raises the risk of splitting when you do water thoroughly again.

A rough guide for a 30–45 litre bag is 2–4 litres of water per session in hot summer weather, more often if the bag sits in full sun all day and less in cooler or overcast conditions. Water at the base rather than over the foliage, and ideally in the morning so any moisture on the leaves has time to dry before evening — that helps keep fungal problems down.

Feed moderately with a balanced fertiliser, ideally one relatively higher in potassium than nitrogen. Too much nitrogen produces lush, leafy growth at the expense of tuber formation underground. Our guide to NPK fertiliser explains what each nutrient actually does if you want the full picture.

A solid routine is a light feed at planting, some compost or well-rotted manure mixed into the soil, then a liquid feed once or twice during the growing season — for example, when the plant starts flowering. Always water in alongside feeding so nutrients reach the roots instead of sitting in the top layer of soil.

Which varieties do best in bags?

Early varieties tend to outperform late ones in bags, because the growing season in a container can feel shorter and more exposed to weather swings. Early potatoes also finish forming tubers before late-summer humidity raises the risk of blight.

Maincrop varieties still work in bags, but they need a larger container, more soil topped up through the season, and patience. If you're only planting one bag and want a predictable result, an early or second early variety is the safer bet.

Think about how you'll use the potatoes, too. Waxy varieties like Charlotte and Annabelle hold their shape well and suit salads and boiling, while floury varieties like King Edward and Maris Piper are better for mashing or baking. Skin and flesh colour vary between varieties, but that doesn't affect how well they grow in a bag — it's mostly a question of how you plan to cook them.

When can you plant potatoes in a bag?

The advantage of a bag is that you can plant earlier than you would in open ground, because you can move the bag under cover or wrap it during a frosty night. Exact timing depends heavily on your local climate, so treat the ranges below as a starting point rather than a fixed calendar.

If you have a greenhouse, sunroom, or even a bright garage, setting the bag there a couple of weeks before moving it outside permanently gives the plant a sheltered head start without you needing to worry about a late frost catching it off guard. For the fuller picture on timing potatoes in open ground, including what actually determines the right date in your specific climate, see our guide on when to plant potatoes.

When are bag-grown potatoes ready?

New potatoes can usually be felt for once the plant has flowered, typically from around 10 weeks. Reach carefully down the side of the bag and feel for tubers about the size of a hen's egg. Take only what you need at that point — the rest keep growing.

For potatoes that will store well, wait until the foliage starts to yellow and die back, usually 14–16 weeks depending on the variety. By then the skins have thickened, which makes the tubers noticeably more resistant to bruising and rot in storage.

Harvesting is where bags really pay off: no fork required. Lay a tarp on the ground, tip the whole bag over, and pick through the soil by hand. It's fast, and you're far less likely to accidentally spear a tuber than when digging with a fork in open ground.

If you plan to store the harvest rather than eat it that evening, let the potatoes dry in the shade for a couple of hours right after harvesting so loose soil on the skin dries and brushes off easily. Don't wash them until just before use — moisture against the skin during storage speeds up rot. Store in a dark, cool spot, ideally around 4–8°C (39–46°F), in a paper sack or wooden crate rather than a sealed plastic bag.

Common mistakes with potatoes in bags

Most bag-related potato problems trace back to one of a handful of simple causes: an undersized bag, inconsistent watering, or not hilling enough. If any of these sound familiar, you already know where to start next season.

• Bag too small. Under about 5 gallons (20 litres) rarely produces more than a handful of small potatoes per plant.
• No drainage, or not enough of it. Without proper holes, the soil turns waterlogged fast and roots quickly struggle.
• Inconsistent watering. Letting the soil swing between bone-dry and soaked produces a smaller, less even harvest.
• Not hilling enough. Skimping on soil limits how many tubers can form, and raises the risk of green, unusable potatoes.
• Too much nitrogen-heavy fertiliser. Produces lush foliage at the expense of tubers underground.
• Harvesting too early out of impatience. Give it another week if you want potatoes that store well, not just fresh new potatoes for dinner that night.
• Wrong spot. A bag tucked in part-shade behind the house will noticeably underperform one in full sun. It's worth moving the bag once during the season if the light changes.
• Forgetting to water during a holiday. A bag dries out far faster than a bed in open ground. Ask a neighbour to water, or set up a simple drip system if you know you'll be away for a week or more.

Frequently asked questions

Can I grow potatoes in a bag on a balcony with no soil contact?
Yes — that's exactly the situation bag growing works best for. Stand the bag on a tray or saucer to catch drainage water so it doesn't damage the balcony floor, and make sure the bag gets at least six hours of direct sun a day.

How many potatoes will I get from one bag?
Expect roughly 0.5–1 kg (1–2 lb) per seed potato in a well-managed bag, so around 1.5–4 kg (3–9 lb) total depending on bag size and variety. Weather, even watering and enough sun matter at least as much as the variety — a sunny, well-tended season can beat these figures comfortably.

Can I reuse the soil from the bag next year?
Yes, but not for growing potatoes again straight away. Potatoes are prone to soil-borne diseases that build up with repeated use, so use the old soil for other crops instead, or work it into a composting bed. New potatoes do best in fresh or well-rested soil.

Do I need to cut drainage holes in a plastic bag myself?
Yes, definitely. Without proper drainage holes, the bottom of the bag becomes waterlogged and roots are starved of oxygen, which can rot the whole plant from below. Cut several holes, roughly 1–2 cm (half an inch) across, spread evenly over the base, plus a few extra up the sides if the bag will sit on a completely sealed surface like concrete or a balcony tile.

Can I plant a second round of potatoes in bags the same season?
Yes, with an early variety you can often fit in a second round if you harvest the first by midsummer and have enough growing season left where you live. Make sure there are at least 10–12 weeks left before your first expected frost before planting a new round, and refresh the soil completely between rounds to reduce disease build-up.

Why are my bag-grown potatoes small and few?
The usual culprits are a bag that's too small, seed potatoes planted too close together, inconsistent watering, or not enough hilling. Also check how much direct sun the bag actually gets — shade for a large part of the day noticeably reduces yield.

Do potatoes in bags need more feeding than potatoes in the ground?
Slightly, yes. Nutrients wash out of a bag more easily during watering or rain because the soil volume is limited and drainage is often better than in open ground. A light supplemental feed once the plant is growing strongly is usually enough to make up the difference.

Can potatoes in bags get blight?
Yes, just like potatoes grown in open ground. Warm, humid weather in late summer raises the risk. Keep the foliage as dry as possible by watering at soil level rather than over the leaves, and see our guide to tomato and potato blight for how to recognise and manage it.

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