How Much Water Do Potatoes Need
I always hated the advice of watering 1 to 3 inches per week for potatoes. Nature just doesn’t work that way. The sun, the wind, and the soil all play a part and sometimes that advice is just plain bad.
Water is really important for potatoes because it affects the quality of the tubers, both in size and quantity. And while potatoes are one of the easier crops I’ve grown, they’re also quite sensitive little fellows and prone to water stress.
I’ve found the trick is to be flexible and here’s how I go about it.
Know Your Soil
Before I get into how I water, when I water, and how often I water potatoes, I think it’s important to talk soil for a minute.
I’ve grown potatoes in heavy clay and I’ve grown them in raised beds using sandy loam soils. This will affect how much you water.
Clay absorbs and holds water like no other. It’s like your hoarder sister (IYKYK). Depending on the weather and the stage of my potatoes, I may only water those grown in clay once per week.
My raised beds are a completely different story. Water doesn’t permeate through the sandy-loamy soil I have in there as well as it does clay. It also doesn’t hold water as well. It’s not uncommon during warm times of the year for me to water potatoes grown in my raised beds every other day.
Containers will be similar to raised beds but will dry out even faster. So the first thing I tell anyone asking about potatoes and water is to know what kind of soil they’re working with.
How To Water Potatoes
I always come up with a water plan before I plant anything. There are many ways to water potatoes, but I’ve found some work better at different stages of the potato’s growth.
Equipment
For example, pre-emergence through small sprouts, soaker hoses, and garden wands work best for me. The plants don’t have an extensive root system yet and can’t seek out water from a drip emitter or vessel. They need you to give them water where they are. And they don’t need a lot of it.
Homemade olla in 3x3 raised bed of potatoes.
When the plant begins to mature, I’ve found that ollas work better than anything; however, they do take up more space. But if you have a 3x3 raised bed, you can put one olla in the middle and plant 6 to 8 potatoes around it and it will provide them with all the water they need.
What’s best about ollas is that they provide water where the potato needs it - deep underground at the roots. Not only are they attractive in a garden, but they also will help you save water.
I use this large Olla from the Olla Company in a 3x3 bed and it works terrifically. It holds a little over 100 ounces and your potato plants will drink when they want to, as they need to. Depending on the weather, you may only need to fill it up once per week.
You can even use a mini olla in grow bags or containers.
Quick note for anyone growing in colder regions. Ollas can crack in the winter if the ground gets too hard and freezes. Most northern gardeners who use them do not use them in the winter. Just a heads up.
My second choice next to ollas is drip emitters. A good .5 gallon per hour drip emitter placed at the base of each plant can provide a nice slow, deep soak for your mature plants.
Water Deep and at the Soil
If you’re not watering with drip lines, ollas, or soaker hoses, I never water from above anymore. I used to take my hose and just hose down the potato garden but every year it led to potato blight, a fungus that can wreak havoc on your tubers.
If you water with a garden wand or watering can, water under the plant at the soil and give it a deep soak. Try not to get the leaves wet.
How Much Water Do Potatoes Need
Well, I could tell you it’s 1 to 3 inches per week but wouldn’t that drive you mad? The honest answer is they need soil that is consistently moist, but not soggy throughout most of their life. Here’s a breakdown of my water plan by potato stage.
Pre-Planting
Before planting, I give the ground a good, deep soak. I want it to retain about 80% of the water I put in it. It should be nice and wet, but not to the point that I can pick up a handful and squeeze water out of it.
Pre-Emergence
After planting, I find that consistently moist soil helps seed potatoes sprout. It’s about balance at this point. Too much water and your seed potatoes will rot.
The goal at this stage should be to keep the soil moist, but not swamp-like.
I’ve also found that it’s not a big deal if the top 2 inches of soil dries out a little bit in between watering at this stage, so don’t sweat it if that happens to you. It’s going to happen because there is no foliage to shade the soil yet.
As your plants get bigger, they will provide shade for the soil beneath them which will help retain water. I also like to companion plant sweet alyssum in between my rows which acts as a shallow ground cover and helps retain moisture. I like to think of it like living mulch because it is shallow-rooted and doesn’t seem to interfere with my tubers.
Emergence
Once the potato plant has emerged from the ground, I start watching my soil moisture like a hawk. When I keep the soil consistently moist it seems to speed up vine growth above the ground. Again, not swamp-like, but moist.
Others stick their fingers in the ground to feel if the soil is moist. I’m a bit more techy and prefer to use a soil moisture meter. The one I use will rate the soil as dry, normal, or wet. I aim to keep the soil at normal levels when I have the meter at least 6 inches deep.
Tuber Formation
Tubers start to form right before the plant begins to flower. Yes, potatoes flower and look very similar to tomato flowers. They are both nightshades. They’ll even produce small fruits that look like cherry tomatoes but don’t eat them.
When the plant is thick and green and is about to start flowering, I step up the moisture a little more. Water is directly correlated to how big the tubers get. Steady water is critical to your crop outcome. Water is what causes your tubers to bulk up.
I aim for about 90% water retention at this stage. Flexibility is key. I always watch for signs of under or over-watering and adjust my water as needed. I’ll talk more about that in a minute.
This is also when I apply a side-dressing of potato fertilizer and water it in really well.
Full Bloom
When flowers start to come out in full bloom, the tubers are about the size of golf balls. This is also when tubers start bulking up and when I pay the closest attention to soil moisture. I keep up with the steady, regular, deep watering so that soil stays moist, but not soggy.
DieBack
Eventually, the potato plants start to yellow and die back. When I first started I confused this with overwatering. Overwatering can also cause leaves to turn yellow. The difference is with overwatering, the leaves will wilt. With dieback, the stems will become discolored as well.
When this happens I stop watering my potato plants and let the soil dry out for about 2 weeks before harvesting. This should also coincide with the number of days the plants have been growing. That’s another indicator that it’s dieback and not overwatering.
By stopping the water, it allows the skins to cure and toughen up before you dig them up.
How Often To Water Potatoes
If you’ve read this far, then you already know that the answer is going to depend and may change based on weather and stage of growth. Rather than tell you I water 2 times per week, I’ll share how I come up with a water schedule.
I have a 2-week water chart that I use. For two weeks I go out to my garden every day, at about the same time of day, place my soil moisture meter 6” in the ground, and check the reading. If it says normal, then I don’t need to water. If it is dry, then I water and mark it on my chart.
Within one to two weeks, I know how many days on average I can go between watering. This gives me peace of mind and prevents me from having to check it every day.
If you do the same thing, just be aware of any severe changes in weather or sunlight that could affect your schedule.
Using a Soil Moisture Meter to Determine How Long to Water
One of the biggest mistakes I see new gardeners make is watering loamy soil, thinking that they’ve given it a good soak, and then being surprised when their plants show water deficiency. I did it too.
Many of us are surprised at how long it takes for water to permeate through loamy soils. Whether you’re watering by hand with a garden wand or using a drip emitter, I like to place my moisture meter in the ground 6” and water until it says normal.
I then count the seconds it took for the water to reach that depth. This tells me how long I need to water with any given method before the water has permeated through the soil to a deep enough level.
For example, with my garden wand, I have to water a particular spot for at least 20 seconds before the water permeates to a depth of 6 inches. For my 3x6 garden beds, that’s about 60 to 80 seconds per bed.
Fall vs Spring Planting in the SouthWest
I live in Southern California which means I have the luxury of planting potatoes two times per year. I always find that I water more often in the fall than in the spring.
It’s dry here in the fall and it’s warm. I’ve found that planting potatoes at the end of August tends to work out best for fall gardens and that means the temperature is still in the 80’s and 90’s Fahrenheit.
Whereas in the spring, the weather is cooler and there’s more cloud cover so I don’t need to water as often.
For example, it’s now the beginning of September in Southern California. I water my potato plants in clay soil about every 4 to 5 days. But I water the potatoes in my raised beds every other day, sometimes every day because the loamy soil dries out much faster.
Signs of Underwatering Potatoes
My plants can’t speak, but they do show signs when they are thirsty or have too much water.
Wilting leaves and drooping is almost a sure sign that the potato plant needs more water. If you see these signs, check the soil and if it’s dry, give them some water.
Underwatering can lead to small golf ball-sized tubers, cracking, and tubers with knots. None of which are all that exciting when it’s time to dig them up.
Signs of Overwatering Potatoes
Watering potatoes is all about balance. If you notice yellowing leaves and wilting, the plant probably has too much water.
I used to always get this confused with underwatering. Basically, wilting with yellow is overwatering. Wilting with leaves drooping is underwatering.
Overwatering can lead to root rot which is a fungus that will turn your potatoes to mush. I had this happen one year and it was very disappointing.
If you see signs of overwatering, I would consider repotting the plant somewhere with better drainage if it’s not too late. Also, let the soil dry out a little bit before you water again. If the top two inches are dry before your next watering session, that’s ok.
Potatoes like to be moist, not flooded. Think lazy river - steady slow water. Don’t put them in a flash flood.
Best Time of Day to Water Potatoes
The best time of day to water potatoes is in the morning. This will result in the least amount of water evaporation from the soil. The second best time I’ve found is in the evening, about an hour before the sun goes down.
Watering Potato Seeds
While it’s not common to grow potatoes from true seeds, it is possible. For the past several years I’ve been growing Clancy Potatoes from Botanical Interests which come in seed form.
The rules are a little bit different because pre-emergence it’s not necessary for water to permeate deep into the soil. The seed only sits in the top inch of soil.
If you grow potatoes from true seeds, you only need to water the top two inches and keep it consistently moist until the seed germinates and sprouts. As the potato matures, water it like any other potato plant.
Watering Potatoes FAQ
Do Potatoes Need to Be Watered Daily?
No. At the most, I’ve only ever watered potato plants every other day and that’s in quick-draining soil in raised beds or containers.
It’s best to come up with a water schedule that keeps the soil moist, but not waterlogged.
Can You Overwater Potatoes?
Yes, it’s a common thing that happens to gardeners. If the leaves start to yellow and wilt, that is a sign of overwatering. If it’s excessive, it can cause the tubers to rot and turn to mush.
Do Potatoes Need A Lot of Water to Grow?
They need a good amount of water, especially once they set tubers. Water is a key for tubers to bulk up. Too little water and you’ll end up with tiny goofball-sized potatoes.
When to Stop Watering Potatoes?
When the leaves start to die back, it’s time to stop watering. Check your calendar to make sure it coincides with the number of days your plants have been in the ground because it’s easy to confuse with underwatering symptoms.
Two weeks before you harvest your potatoes, it’s best to stop watering them so that the skins cure and toughen up.
Do Potatoes Like Moist or Dry Soil?
Potatoes like consistently moist soil.
