Watering Needs for Potatoes
One of the keys to growing potatoes in containers is keeping your soil mix moist, not wet. To check moisture level, stick your finger into the soil at least an inch or up to your second knuckle. If it feels dry, water. Check at least once a day. If it’s very hot, and or windy, you may have to water your potato container gardens even more than once a day. Make sure to water deeply, until water runs out the bottom. It is counter productive to just water the surface of the soil.
Fertilizer Needs Of Potatoes In Containers
Potatoes are considered “light” feeders among the vegetable community. If you use too much fertilizer all the plant’s energy will go to growing wonderful foliage and little energy will go to producing potatoes. So be warned. If you mixed a modest amount of granular organic fertilizer in the potting mixture, then that is all the granular fertilizer your plants will need.
However, a spray of fish emulsion with kelp every three or four weeks until harvest will be welcomed by the potato plants and not hurt production.
Hilling Potatoes In Containers
Once your potato plants have grown around six inches, you are going to “hill" them by adding a new layer with a combination of soil, potting mix, and compost. You want to add a couple of inches of a the mixture around your potato plants. Be careful not to break the plants while doing this.
You will be covering some of the leaves of your potato plants with your soil mix, but you want at least 2/3 of the plant with its leaves to be sticking out of the soil.
Keep Hilling Your Potatoes As They Grow - You’ll want to repeat this hilling process of adding a soil/compost mix a few times more as your plants grow or until your soil reaches a few inches from the top of your container leaving room for a couple of inches of straw mulch.
Harvesting Potatoes Grown In Containers
The first potatoes will be ready to harvest after around two months. You can begin to harvest potatoes any time after the plants have flowered. To harvest potatoes, simply poke around in the potting soil with your hands, feeling the size of each potato you encounter. If it is the size you want, pull it up. Otherwise, leave it alone and it will continue to grow. Each plant should produce about 2 to 4 pounds of potatoes, depending on the variety.
You can also wait until the plants turn yellow and die back and then harvest all of the potatoes. The easiest way to do this is to turn the container over dump it out into a wheelbarrow or onto a tarp. Then you can freely paw through the soil to find all of the potatoes. You may find some really tiny potatoes - don't chuck them- those can be some of the best and sweetest.
After you have harvested all of your potatoes, make sure you remove all of the plants from the soil and dispose of them. If you have used a plastic trash can or tub, you can put the lid on top of the container and leave the soil to use to grow potatoes again next year!
Occasional Problems Of Container Potatoes
One of the only insect problems you are likely to encounter when growing potatoes in containers is the Colorado potato beetle. They may not be a problem where you live, so check with your local county extension office to find out.
If they do show up the adults are light brown with black stripes running down the back. Larvae are reddish or brown, soft-bodied, with two rows of black spots on each side of the body. Both adults and larvae can cause severe feeding damage on leaves and stems. Hand-pick adults and larvae, and crush egg masses whenever practical. The best organic insecticide to control this pest is organic Spinosad.
Early and Late Blight
These fungal diseases affect stems and leaves; however, late blight can also cause tuber rot. Early blight appears as circular spots with concentric, bull's-eye rings, usually on the lower leaves. Late blight occurs mainly during cool, wet weather. Infection appears as large irregular spots, eventually turning brown or black. The under surface of infected leaves often has a white fungal mass. Control of blight involves spraying with an effective fungicide such as Actinovate.