potato plants falling over in a field

10 Reasons Why Your Potato Plants Have Fallen Over

Growing potatoes in your backyard or garden isn’t difficult. With proper care, you can expect to harvest two to five pounds of potatoes from each plant, depending on the variety and growing conditions.

Sometimes, problems arise, like the tops of the potato plants falling over. This can happen for several reasons. Find out why your potato plants are falling over and if there is anything you can do to prevent it.


 1. Massive tops from too much nitrogen

All plants need nitrogen to grow, and potatoes are no exception. However, too much nitrogen can lead to the development of huge tops on your potatoes. When this happens, they are more likely to fall over or flop due to the weight of the stems and foliage.

The most common cause of in the soil is using too much composted (or fresh manure). If you use manure in your garden, do so sparingly if you notice plants with deep green leafy tops. Too much nitrogen will cause rapid stem and leaf growth but inhibit the formation of tubers.

If the problem persists for more than one year, consider using a potato fertilizer lower in nitrogen, such as 5-10-10, when you plant your potatoes.

2. Not enough soil around the base of the plant

Potato plants need to be ‘hilled’ to provide room for the tubers to grow and help support the plant if they were planted shallow or close to the surface of the soil. Hilling should be done when the plants are about a foot tall. Hill them by mounding soil around the base of the plants leaving a few inches of the stem and at least one set of leaves above the ground.

Many gardeners hill their potatoes two or three times during the season, making the mound higher each time. The stems of the potato plant will form new roots along the buried stem creating a robust root system that can support the weight of the plant.

Alternatively, you can plant your potatoes deeper in the spring, around 6 to 8 inches deep should be deep enough to provide plenty of soil coverage and support for the potato plant stems and emerging potatoes.


3. Drought

Drought can also cause the tops of your potato plants to fall over. The cause is twofold. First, plants that do not get enough water cannot maintain turgor, the pressure inside the plant tissue that makes stems rigid. When this happens, the stems and leaves wilt and flop to the ground.

potato plants blown over in periods of drought
Dry periods will weaken potato plant stems making them vulnerable in windy conditions.

Dry soil in a drought also contributes to stems falling over because dry soil becomes loose and does not provide a solid support for the roots of your potato plants. Your plants may flop over in extremely dry soil, and some roots may be exposed.

Water your potatoes regularly to prevent over-dry soil.

4. High winds

High winds can wreak havoc with your potato plants by either breaking the stems or simply blowing the tops over. If the stems are unbroken, the plants may revive and straighten up after a wind storm. Broken stems will continue to grow if you cut them back.

You can also prevent toppling tops from the wind with support with a stake to help them recover. Likewise, consider hilling the potatoes a little higher to support the stems.

To avoid issues with potato plants falling over due to high winds, avoid planting in extremely windy locations, such as near an exposed coastal region or mountain top.

5. Heavy rain

Like high winds, heavy rain can lead to toppled potato plants as it pelts the foliage with water. The force of the rain plus the added weight on rain-covered stems may be more than your plants can withstand and send them toppling to the ground.

Like potato tops that have fallen over due to high winds, the stems may recover as long as they are not broken. You can help them by providing temporary support with stakes or mounding more soil around the base of the plants.

6. Not enough sunlight

Potatoes grown in low light may develop tall, spindly stems as they stretch to reach the light. Spindly stems tend to break or bend easily as they are not strong enough to support the increased weight of the growing stem and foliage.

To avoid potato plants falling over from spindly stems, grow them in an area that receives 6 to 8 hours of direct sunlight daily. Avoid growing tall plants, like corn, or placing a trellis where the plants will cast shade on your potatoes.

thin stems on potato plants are easily blown over
Thin stems are easily blown over in windy conditions.

7. Pests  

Pests and diseases weaken your potato plants and may cause the tops to fall over. Some of the most common culprits are:

Colorado Potato Beetle

These beetles overwinter in the soil and appear in the spring when potato seedlings emerge from the soil. Adults are yellow/tan with dark stripes and have a hard shell like other beetles. The adult lays clusters of tiny orange eggs on the underside of the leaves.

When the eggs hatch, the larvae eat the potato foliage and even eat the blooms on potato plants. These orange/red larvae grow rapidly, devouring the plants until they drop to the ground and enter the soil to pupate.

The damage from the Colorado Potato Beetle can cause the tops of your potato plants to fall over. Treat Colorado Potato Beetles as soon as the first adults appear in the spring either by handpicking them and dropping them in a bucket of soapy water or by applying pesticides labeled to treat Colorado Potato Beetles.

Cutworms

Cutworms live in the soil and attack plants when they are young and tender. They cut the foliage off at the ground level. To prevent cutworms from nipping off your potatoes, sprinkle diatomaceous earth around the plants when they first come poke through the soil.

8. Disease

Blight

Potato blight can sometimes cause the tops of your potatoes to fall over. This disease is caused by the Phytophthora infestans fungus. This fungus can be either soilborne or airborne. When the fungal spores reach your potato plants they begin actively growing when weather conditions are right — usually in cold, wet weather.

The first signs of blight are small black spots, but the infection moves quickly. Black spots enlarge and spread from leaf to leaf, killing the foliage in days. The spores can also attack the tubers beneath the soil and cause them to rot.

potato blight on plant leaves
Black spots of potato blight on the leaves. Blight will quickly blacken and kill the entire plant if not treated.

The stems and branches of a potato plant infected with blight may topple to the ground before dying completely. It is easy to determine if it is blight as the whole plant will quickly turn black and die.

The best way to avoid blight on potatoes is to plant certified seed potatoes and rotate the vegetables in your garden. Avoid growing potatoes in the same location each year.


9. Potatoes have fully matured 

Potato plants die back and fall to the ground naturally when they mature, and they no longer need the stems and foliage to provide nutrients for the growing tubers. This typically happens in the fall. To determine if your potatoes have reached maturity, check the days to maturity for the variety you are growing. You can also dig into the soil to check if the tubers have reached full size.

No action is needed if the potato tops die back because they are mature. You can even leave the tubers under the soil for 2 to 3 weeks before harvesting them.

10. A combination of many

Sometimes it is not just one of the above factors but a combination of many factors which cause your plants to fall over. Perhaps your potato plants have been thriving and then you get a week of dry weather which weakens the plant slightly, then you get a day of high winds which due to having a slightly weakened stem blows over a lot of plants. These are just two points that when combined made some of your potato plants fall over. There is nothing really you can do about this- just accept it as part of nature.

Summary

Seeing your potato plants falling over can be disheartening, but don’t lose hope. Usually, a potato plant that has fallen over will not mean the end of its growth unless the stem has been fully separated from the roots. There are many causes of potato plants toppling over, from simple weather-related factors like high winds, heavy rain, or drought to more severe conditions like garden pests or diseases. Sometimes an over-application of fertilizer -for example, excess nitrogen- can be the underlying cause, so it usually pays off to make your fertilizer calculations based on a soil sample rather than guesswork.