Every home gardener knows the importance of water, but when it comes to potatoes, things can get a little confusing. Potatoes are a special case; they need just the right amount — too little and they’ll produce small, misshapen tubers; too much and they can develop rot. So, how often should you water potatoes, and when should you stop?
Potatoes require frequent, constant moisture — especially during early stages of growth. A good rule of thumb is to water every 3-5 days, or whenever the soil feels dry. Once the potatoes mature and the tops begin to die back, you can reduce watering and then stop completely 2 weeks before harvest.
When it comes to watering potatoes, a balance is key. But it’s not easy to figure out the right time to water just by looking at your plants. Since the tubers are growing underground, they can’t tell you when they’re thirsty! Let’s take a closer look at what signs to keep an eye out for and how often you should water your potatoes.
How Do You Know When to Water Potatoes?
Potatoes thrive in well-saturated, moist soil but don’t like to sit in soggy conditions. So the best way to tell when they need watering is to feel the soil. Insert your finger or a small stick in the soil near the potato plant.
If the soil is dry more than an inch below the surface, it’s time to water. If it feels damp or cool down there, the potatoes are probably getting enough moisture, and you can leave them for a day or two longer.
Another way to tell if your potatoes need water is to look at the plants themselves. If the leaves are wilting or drooping, or there are brown or yellow spots on the leaves, this is a sign that the plant is stressed and needs water.
However, wilting leaves are also a sign of too much water or high temperature, so it’s important to check the soil before you assume that your plants need water just by looking at them.
How Often Do You Need to Water Potatoes?
As a general rule of thumb, potatoes need about 1-2 inches of water per week. This is equivalent to about 10-20 gallons of water per 100 square feet. And this shouldn’t be all at once — potatoes do best when they get frequent light watering throughout the week. This means you should water potatoes at least twice a week.
Of course, there are always exceptions to the rule. Your climate, daily temperature, the type of potato you’re growing, and the growth stage will all affect how much and how often you need to water your plants. Let’s look at a few of these factors in more detail.
Type of Potato
There are two main types of potatoes — waxy and starchy. Waxy potatoes have a lower starch content, more moisture, thin skin, and a delicate flavor. Starchy potatoes, on the other hand, have a higher starch content, less moisture, thick skin, and robust flavor; they’re also more drought-resistant. So, if you’re growing waxy potatoes, you’ll need to water them more often than starchy potatoes.
Temperature, rainfall, humidity, and wind all affect how often you need to water your potatoes. In rainier months, for example, most of the water requirements are fulfilled by rainfall, so you won’t need to water them as often. Similarly, in hot and dry conditions, you’ll need to water more frequently to make sure the plants don’t stress — and the potatoes don’t start to shrivel.
Stage of Growth
Potato growth is divided into four stages: germination, vegetative growth, tuber bulking, and harvest. The first three stages are when the potato plant is actively growing and will need constant moisture to produce strong, healthy plants and plentiful tubers.
In the fourth stage, however, potato plants stop growing and start to mature. At this point, you’ll need to cut back on watering to prevent the tubers from splitting or rotting. And then, you can eventually stop watering before harvest.
The water requirement for each stage is as follows:
- Early Growth Stage: 4 weeks after planting — Water every 4, 5 days
- Vegetative Growth Stage: 2 months — Water every other day
- Tuber Bulking: 3 months — Water 4 times a week
- Harvesting: 4th month — Gradually cut back on watering and stop 2 weeks before harvest
Remember that potatoes don’t like soggy conditions, so when we’re talking about multiple waterings per week, it’s really just a case of giving them a light sprinkling each time to keep the soil moist. This schedule works well if you have drip irrigation (on Amazon) or soaker hoses (also on Amazon) in your potato patch.
Can You Overwater Potatoes?
Yes, it’s possible to overwater potatoes. This is more likely to happen if the potatoes are grown in poorly drained soil or if you’ve applied too much water at once. Whatever the case may be, overwatering is detrimental to both the quality and yield of the potato crop and, in severe cases, can lead to plant death.
Some common risks and problems associated with overwatering potatoes are:
- Misshaped tubers: In the rapid growth stage, potato tubers start to swell. If the plant is overwatered during this time, the tubers grow into odd, lumpy shapes, which aren’t as desirable to consumers and fetch a lower price.
- Blight: This is a serious fungal disease that thrives in wet conditions. The leaves of the plant turn yellow and brown before eventually dying. If left unchecked, blight can spread quickly and decimate an entire potato crop.
- Powdery Scab: Another fungal disease favored by wet conditions, powdery scab manifests as small, scabby, purplish-brown lesions on the surface of the potato. These spots eventually turn into raised, corky blisters. Along with lowering the quality of the potato, powdery scabs make potatoes vulnerable to soft rot bacteria during storage.
- Lenticel Development: When potatoes can’t get enough oxygen from the soil, they start to develop raised bumps on their skin to help them breathe — these are called lenticels. Like scabs, they lower the quality of the potato and make them more susceptible to storage rot.
- Rot: In extreme cases, waterlogged soil completely blocks the oxygen supply to the potato plant. This causes the roots to suffocate and die, eventually leading to the death of the entire plant. Rot manifests as rotten, mushy potatoes that are totally unsuitable for eating.
If you think your potatoes are being overwatered, the best course of action is to reduce watering immediately and make sure the soil has adequate drainage. You may also need to add some organic matter, such as compost, to help improve drainage. If the problem persists, it’s best to consult with a local plant expert.
When Should You Stop Watering Potatoes?
Potatoes need water until they’re fully grown, which is about three months after planting. By this time, the tubers reach their full size, and the plant’s foliage begins to yellow and die back. So, there is no need for water; extra moisture will encourage the growth of mold and mildew.
The rule of thumb is to stop watering about two weeks before harvest. If you live in an area with high humidity, you may need to stop watering even earlier. This will allow the potatoes to begin the curing process, which helps improve their flavor and texture.
The potatoes grow thicker skins, which helps protect them from bruising and damage during harvest and transport. Plus, it’s easier to dig up potatoes when the soil is dry — wet soil sticks to the tubers, making it difficult to dig and clean them.