How to Grow Potatoes in a Bag

Planting the Potatoes

Wait until the spring to plant your potatoes. Before you begin the process, it’s important to make sure the danger of frost has passed. Most potatoes should be planted between March and April. However, you can start as early as February, as long as you have a safe place to store the bag, such as a greenhouse or conservatory. Consult The Old Farmer’s Almanac website if you are unsure of local frost dates.

Find a warm, sunny spot for the grow bag. You want to pick a spot with the most access to sunlight and rainfall. You should make sure that your potatoes get at least 6-8 hours of direct sunlight. This will ensure that your grow bag has a maximum yield. Keeping your grow bag on a patio or balcony is a good way to keep it safe from curious animals.

Chit your seed potatoes. Give your potatoes a head start by allowing them to sprout before planting. This process, called “chitting,” encourages faster growth and fuller harvests. In order to chit your potatoes, place them in an empty egg box or seed tray and leave them in a warm environment for approximately 4 weeks. Once they have begun to sprout, you can cut the potatoes into smaller chunks, or simply plant them whole.

Make sure your soil contains a healthy mixture of compost and topsoil. In general, you should aim for a 60/40 ratio of compost to topsoil. Find a wheelbarrow or tub that can hold all your soil at once. Next, dump your soil into the container and mix thoroughly. You should only use about ⅓ of the soil on planting day. Set aside the rest to use throughout the growth process. Potato fertilizer is optional but recommended for a maximum yield.

Fill the bag with 4 inches (10 cm) of soil mix. You can find grow bags at most hardware or garden supply stores. Fold down the edge of the bag until you have an approximately 4 inches (10 cm) cuff. Pour in your soil mixture until its about 4 inches (10 cm) deep. Next, spread the potatoes evenly across the surface. Cover with an additional 3 inches (7.6 cm) of soil before watering.

Caring for the Potatoes

Add soil as needed. When your potatoes have grown approximately 8 inches (20 cm), you know it's time to add more soil. Unfold the edge of the bag and add an additional 4 inches (10 cm) of your soil/compost mix. As the plants grow, gently repeat this process until the soil level reaches just below the top of the bag.

Water the bag regularly. It’s important to keep your soil moist but not saturated. Although, occasional heavy watering is better than regular light watering as the water needs to get all the way down to the lower roots. During the summer it may be necessary to water the plants daily to prevent the soil from drying up. Pay close attention to watering and your plant should grow into the summer.

Watch out for pests. You should monitor your potatoes regularly to prevent pesky insects from laying their eggs. The most common culprit is the Colorado potato beetle. Make sure to check your foliage for tiny clusters of yellow eggs. If you find any on your plants, simply pick them off with your hand and place them in a bucket of soapy water. Potato Blight can be a problem for later yielding crops. You can protect against this fungal disease with a Vitax Bourdeau Mixture, a traditional, protective fungicide, available in the ‘pest control’ section of your local hardware or garden supply store.

Harvesting the Potatoes

Harvest the early varieties of potato first. These potatoes should be harvested first as they do not store well. These potatoes are best harvested in small quantities and eaten when fresh. First and second earlies are best harvested during June-July, when the flowers are fully mature and open. Use a small spade or garden fork to gently remove the potatoes. You don’t want to be too intrusive or you run the risk of interrupting the growth process for your main crop.

Wait for the leaves to wither. Main crop varieties can be harvested from September onwards. However, towards the end of the season you will begin to notice the leaves turn yellow and begin to wither. At this point, you can stop the watering process. Leave the potatoes for another week or so before harvesting.

Dump the bag. Once your potatoes are ready to harvest, dump the entire bag into a wheelbarrow or tub. Dig through the soil to find your potatoes. A regular grow bag holds around 50 US quarts (47 L) and should yield at least 7 pounds (3.2 kg) of potatoes. After you’re finished, add the soil to your garden or compost. If the weather is dry, allow the potatoes to sit, unwashed for 2-3 days. This curing step allows the skin to mature and will protect your potatoes during storage. Clean out the bag and store it away until next year.

Store your potatoes. After harvesting, let your spuds dry out in a cool, dry area. Once they are dry, the potatoes can be stored in a hessian or mesh sack. Avoid storing them in a plastic bag as the potatoes will “sweat” and begin to rot. Store potatoes separate from onions and fruit. These give off ethylene gas that can cause your potatoes to sprout prematurely. Store your potatoes in the dark. Prolonged exposure to light can cause a chemical build up that will cause potatoes to turn green and produce a bitter taste. This has been known to cause illness if consumed in large quantities.