Skip the Bucket and Grow Your Potatoes in a Bag

Quick answer: A 10-gallon fabric grow bag is the best way to grow potatoes for most people. A raised bed gives you more potatoes per dollar if you've got the room. The five-gallon bucket is the one that disappoints, and the reason is heat, not size.

Last July my neighbor tipped over a black hardware-store bucket he'd planted in April. He'd watered it faithfully and the vines had looked great. Inside he found four potatoes the size of golf balls and a lot of dirt. He blamed the variety. The variety was fine. The bucket had spent June baking on a south-facing driveway, and potatoes don't form tubers when the soil gets that hot.

That's the whole story of growing potatoes. Every container works on paper. One of them fights you all summer.

Timing beats the container

Potatoes are a cool-season crop that people treat like a summer one. Tubers form best in cool soil and slow down badly once the soil gets into the upper 70s and past 80°F. The leaves can look lush the whole time while nothing happens underground.

So plant early. The usual rule is two to four weeks before your last frost date, once the soil is around 45°F and isn't soggy. A light frost will nip the first shoots. They regrow. A hard freeze is a different matter, so keep an old sheet handy.

Roughly, by region:

• Zones 3 to 5: late April into May. One crop, harvested late summer.
• Zones 6 and 7: March into April. You can try an early variety for a summer harvest.
• Zones 8 to 10: late January into February for a spring crop, and a second planting in late summer or fall in many areas. Planting in May in Texas or Florida is how you grow very healthy-looking vines with nothing under them.

If you don't know your number, check your hardiness zone before you buy anything. The zone decides your calendar, and the calendar matters more than which container you pick.

Buy seed potatoes, not grocery potatoes

Grocery-store potatoes are often treated to slow sprouting, and they aren't certified disease-free. You can get a crop out of them. You can also bring blight or scab into your soil, and then it's yours for years.

Certified seed potatoes cost a few dollars a pound at a garden center or feed store in early spring. Mail-order costs more and gives you more choice. A pound or two fills a couple of bags.

Varieties worth starting with:

• Yukon Gold. Forgiving, early to mid-season, and good at everything in the kitchen.
• Red Norland. Early. Good for a southern spring crop or a short northern summer.
• Kennebec. A dependable white, a little later, good keeper.

Skip Russet Burbank your first year. It's the classic baker, but it wants a long, even season and punishes uneven watering with knobby, misshapen spuds.

Cut anything bigger than an egg into pieces with at least two eyes each. Then leave them on a counter for a day or two so the cut sides dry and callus. If you plant them wet, they rot.

The bag: the winner for most yards

A 10-gallon fabric grow bag is about the right size for three seed pieces, maybe four. Fabric breathes. Water drains out the sides and the bottom, and the air moving through the walls keeps the soil cooler than plastic ever will. That cooler soil is why the bag beats the bucket.

What it costs, roughly: grow bags usually run under ten dollars each in multipacks. A 10-gallon bag holds about 1.3 cubic feet, so one 1.5-cubic-foot bag of potting mix fills it, at around twelve to fifteen dollars. Add the seed potatoes and you're under thirty dollars for the first bag, and less after that, since the bags last several seasons.

How to plant:

1. Roll the sides of the bag down by half. You'll unroll them as you go.
2. Put in four inches of potting mix with a handful of compost or a balanced vegetable fertilizer.
3. Set three seed pieces on top, cut side down, eyes up, spaced apart.
4. Cover with three inches of mix and water it in.
5. When the shoots are six to eight inches tall, add mix until only the top couple of inches of leaves show. Unroll the bag as needed.
6. Repeat until the bag is full, then stop and let them grow.

Use potting mix or a mix of compost and potting mix. Don't use garden soil. In a container it packs down like brick.

The annoying part: bags dry out fast. By July you may be watering every day, sometimes twice in a heat wave. Uneven watering, where the bag goes bone-dry and then gets flooded, gives you cracked and hollow potatoes. Stick a finger in. If the top inch is dry, water until it runs out the bottom.

The bucket: possible, but it's the trap

You can grow potatoes in a five-gallon bucket. A dark plastic one in full sun will cook the roots, it's too small for more than two seed pieces, and it doesn't drain unless you drill it.

If you're set on buckets, make it worth your while. Drill eight to ten half-inch holes in the bottom and a few around the lower sides. Use a white or light-colored bucket, or wrap a dark one in burlap. Put it where it gets afternoon shade. Plant two seed pieces, not four. Expect a modest harvest and be pleasantly surprised if you get more.

It's the right choice for exactly one person: someone with a balcony, a free bucket and no budget. Everyone else should spend the eight dollars on a bag.

The bed: more food, more work

If you have a raised bed, potatoes do very well in it. A 4x8 bed for under two hundred dollars can take around thirty seed pieces on a 12-inch grid, and per dollar it'll out-produce a row of bags. Ground soil also stays cooler and evener than any container, so watering is easier.

Dig a trench or holes about six inches deep, set the pieces 12 inches apart, and cover with three or four inches of soil. When the plants reach eight inches, pull soil or compost up around the stems, leaving the top few inches of leaf exposed. Do it once more two or three weeks later. Then mulch with six inches of straw to hold moisture and keep the soil cool.

The trade-offs are real. Potatoes like slightly acidic soil, and in alkaline soil they get scab, those rough corky patches on the skin. Scab is ugly but harmless once you peel it. Potatoes also belong to the same family as tomatoes, peppers and eggplant, so don't plant any of them in that bed for about three years afterward, or disease builds up in the soil. That makes it a bed you've committed. With bags, you just dump the old mix and move on.

About those potato towers

You've seen the pitch: keep adding soil to a tall stack, the plant keeps making potatoes all the way up, and you harvest a barrel's worth. Mostly it doesn't work like that. Many common varieties, including the early ones, set their tubers in one layer near the original seed piece. Burying the stem deeper gets you a taller plant and the same amount of potatoes. Some late varieties set a little higher along the buried stem, but nobody's filling a whole tower from one row of seed. Hill enough to keep the tubers covered and stop there.

What goes wrong

• Green potatoes. Light hits the tuber and it turns green, which means solanine, and that's mildly toxic. Cut away green spots generously, and throw out any potato that's green all over. Fix it by keeping them covered with soil or mix.
• Colorado potato beetles. Striped adults, fat orange larvae and bright orange egg clusters under the leaves. Check every couple of days, pick them off into soapy water and squash the eggs. Do this early and you'll stay ahead of them.
• Rot. Usually from planting freshly cut pieces or from a container that won't drain.
• Vines and no tubers. Usually heat, too much nitrogen, or both. Ease off the lawn-type fertilizer.

Harvest is the good part

For new potatoes, reach into the bag a couple of weeks after the plants flower and pull a few small ones. Leave the rest.

For storage potatoes, wait until the vines yellow and die back, then wait two more weeks so the skins toughen. With a bag, lay a tarp on the ground, tip the bag over and dig through with your hands. This is the best moment of the gardening year, and anybody under ten will want to do it for you. Let them.

Brush off the dirt but don't wash them. Cure them for a week or two somewhere dark and cool, around 50 to 60°F, then store them somewhere dark at 40 to 50°F. Eat the nicked ones first.

Then put the spent mix to use. Spread it on a flower bed or work it into your compost pile, not back into next year's potato bag. Shake out the fabric bag, dry it in the sun and fold it away clean. Next spring you'll be glad it's ready to go.