Potatoes grow best when they have a steady supply of 2-3 inches of water per week without fully drying out.
Potato plants should be watered deeply, especially if it gets very hot and dry. The soil should be moist 8 to 10 inches underground.
Make sure not to overwater the potatoes for 2 weeks after planting. Watering every 4 to 5 days is usually enough during the first weeks after planting.
Water the plants every day or two, 6 to 8 weeks after planting. This is when the plants will begin making new potatoes underground. Doing this will help the potatoes grow bigger and more evenly.
How to grow potatoes
If you would like more information about growing your own potatoes, please read my article about how to grow your own potatoes. This covers everything you need to know from planting, preparing seed, growing, harvesting, storage and more about this great vegetable.
How often to water potatoes
When growing potato plants, make sure they have enough water during the growing season, this will help maximize the amount and quality of potatoes you get at harvest.
Potato plants that don’t have a steady water supply will grow fewer and smaller potatoes. The potatoes will also develop defects like knots, lumps, and cracks as they are growing.
Potatoes that are grown with a steady supply of water will taste better and last longer when stored.
When potatoes are harvested, their skins need to cure and dry. If the skins have cracks and knots the potatoes cannot cure properly and will not store well.
By monitoring your region’s rainfall, checking moisture levels of the soil, and knowing how much moisture the plants need, you can decide how often you need to water your potato plants.
Read on below to learn how to estimate how much to water your plants and how to tell if your plants are not getting the ideal amount of water.
Will the plants tell me when they need watering?
It is normal to see plants drooping due to the heat on summer days but this does not necessarily mean they need watering.
Checking the moisture level of the soil is better than just looking at the plants.
You cannot see how new potatoes are developing and growing underground.
You may not know if your potatoes experienced overly dry or wet conditions until you harvest them.
The potato plant’s leaves will turn yellow and start to die back if it is getting too much water.
How much water do potatoes need?
Potato plants typically need 1-2 inches of water per week. This can come from a combination of natural rainfall and additional watering.
If the climate is especially hot and dry, the plants will need more water. Deeply watering the soil helps to keep the ground cooler during hot periods.
How much rainwater does my region receive?
Check your local weather reports or use a rain gauge like this one to see how much rain you are getting.
Especially while the potatoes are forming underground, 6 to 8 weeks after planting, you should supplement rainfall with watering or irrigation if needed.
How often should I water my plants?
After figuring out how many potatoes to plant then getting them planted and giving them a thorough watering if your soil is dry, wait up to 2 weeks before watering again, as long as the soil doesn’t dry out completely. Keep the soil moist but not wet during these first 2 weeks.
After that, watering your plants every 4 to 5 days after planting is typically enough if your region is experiencing normal rainfall and temperatures.
Check the moisture level of the soil before you water the plants and don’t overwater – the soil should always be moist but never wet.
Increase the frequency of watering if rainfall is scarce or temperatures are high and the soil is dry.
In drier climates, you may want to consider drip irrigation systems to avoid manually watering every day.
How much water should I use?
Potatoes grow best with deep and thorough watering. Most potato roots are shallow but some go quite deep.
Irrigated potato plants get almost a quarter of their water supply from the second foot of underground soil.
The soil should be moist 8 to 10 inches below ground for the deeper roots to absorb water.
You can check that the soil is moist using a common garden soil moisture. Many of these have a probe around 8 inches long that would work for estimating the moisture level.
If the soil is already moist, no additional watering is needed at that time.
What happens if I water my potatoes too much?
Depending on the growing stage, overwatering can have different effects.
Watering too much after planting and not enough while the new tubers are forming can lead to misshapen potatoes.
Overwatering after the plants die back can cause the underground potatoes to rot.
What happens if I don’t water my potatoes enough?
Potatoes need a steady supply of water from planting until the vines begin to die back to grow to their full potential.
You will get fewer, smaller, and more irregular potatoes if you don’t water them enough.
Is it okay to let the soil dry out?
While potatoes can stand some dryness when temperatures are hot.
If the climate is dry and you are experiencing water shortages, it is okay to let the soil dry out at the surface. But if dryness last more than a few days, the plants will begin to die if they are not watered.
If the soil does dry out, water the potato plants deeply and thoroughly.
This will make sure that any potatoes that might be developing underground are not damaged.
When should I stop watering my potato plants?
After 90 to 120 days the vines will begin to turn yellow and die back. This is a natural sign that they are almost ready to harvest.
Stop watering the plants to allow the skins to dry out and cure for about 2 weeks before harvest. Good Luck!
A soil moisture meter can be a good way of confirming your knowledge on whether you need to water your soil or not. If you do decide to get your own I would advise you to use it as a guide, as they usually tell you if the soil is dry, moist, or wet.
As you become more used to checking your soil, there will be less need to have a soil moisture meter. Eventually, you will be able to dig in 6-8 inches with your hand and you will be able to tell if the soil needs water or not.