How Often Should You Water Potato Plants?

It's easy to grow a bountiful crop of potatoes (​Solanum tuberosum​) in a home garden when you know the basics, like how often to water potato plants. A potato plant needs a dependable watering schedule and cool soil temperatures to produce desirable, evenly formed tubers. Too much or too little water can impair tuber formation and jeopardize plant health.

Although some people mistake a potato as a root, it's actually a tuber or an underground storage stem. More than 100 varieties of the potato exist, but white and red-skinned types are commonly grown in home gardens because of their appealing taste and texture.

It's a cool-season crop that grows well throughout most of the U.S., but particular in Northern states that have a shorter growing season. A potato plants needs soil temperatures of about 60 and 70 degrees Fahrenheit in order for tuber formation to occur. If soil temperatures become too warm, 80 degrees Fahrenheit or warmer, tubers don't properly develop. A potato plant can usually tolerate light frost.

When you water potato plants, consistent and even moisture is important. The watering demands also vary based on the growing phase. Too much water can cause rotting while too little water can affect development. It's important not to underwater or overwater young potato plants. If they receive the wrong amount of water in the early stages, the potatoes might become misshapen or not develop well.

Provide enough water to a potato plant so that its soil is moist, but not saturated. A plant doesn't like wet feet. The general rule is to provide it 1 to 2 inches of water per week, including rainfall. In the absence of sufficient rainfall, a consistent watering schedule of once every four to five days is generally ideal for a young plant. Increase the frequency to once every two to three days when tubers form, which happens about the same time the plant flowers, to encourage uniform potatoes. Regular watering also helps keep soil temperatures cooler.

Potatoes need less water as they near harvesting time. This helps them cure, dry and toughen up before you dig them so they can last in storage. Cut back on your watering when the leaves turn yellow and start to die back. Water the potato plants only sporadically when at this point, usually around mid-August.

Drip irrigation from a garden hose works best to water potato plants. Overhead irrigation can injure a young, fragile plant. Furthermore, use of a watering can tends to direct too much water to the top of the plant and too little to its roots where it's needed most. Warm, wet foliage encourages fungal growth and weakens the plant structure.

Over-watering a potato plant causes irregular tuber formation, promotes rot and increases risk of disease. Conversely, under-watering a plant so that its soil dries out completely prohibits canopy and tuber formation and often leads to irregular tubers with various imperfections. The effects of poor watering practices results in a stressed plant that takes several days, even after the issue is corrected, for it to overcome.