Why Are My Potato Plants Falling Over? (Never Do This!)


When your potato plants fall over, it is natural to wonder if they are dying, and if you will get a potato crop at all.  I did some research into what this means, and there are several possible causes.

So, why are your potato plants falling over?  Potato plants will fall over when the plants are mature and ready for harvest.  Potato plants can also fall over if they are too tall due to over fertilization.  Temperature, watering, diseases, and pests can also cause your potato plants to fall over, possibly without producing any potatoes.

If your potato plants are mature, then it is not a concern when they fall over.  However, if they are not mature, then you should investigate the reason it is happening.  Let’s get into the details of what could be causing your potato plants to fall over, and what you can do to prevent it.

Why Are My Potato Plants Falling Over?

One of the most common reasons that potato plants fall over is that they are mature and ready for harvest, so let’s start there.

Your Potato Plants Are Mature And Ready For Harvest

When potato plants reach the end of their life cycle, the part of the plant above ground (the green shoots and leaves) will fall over, usually turning yellow first.  If this happens around the same time that the plant matures, then there is nothing to worry about.

white potato flower
Potato plants will sometimes grow flowers and even above-ground fruit (resembling tomatoes) before maturity!

To calculate the maturity date of your potato plants, it is important to keep track of when you planted them.

Then, check the time to maturity of the potato variety that you planted (you can usually find this information online on the seed packet, on a seed company website, or in the catalog you ordered from).

Keep in mind that the times to maturity for potatoes can vary from 75 days to 160 days.

For example, let’s say you planted Ida Rose potatoes on April 15.  Ida Rose potatoes take 95 to 100 days to grow to maturity.  That means that after 15 days in April, 31 days in May, and 30 days in June, the potatoes would be ready for harvest around July 19th to 24th (15 + 31 + 30 + 19 = 95).

For more information on times to maturity for potato plants, check out this article on growing potatoes from the Oregon State University Extension.

Your Potato Plants Are Too Tall

If your potato plants are falling over long before their maturity date, then there is some other problem to deal with.  One possibility is that the potato plants have grown too tall.

Potato plants will grow too tall due to overfeeding, especially if you use fertilizer that is too heavy in nitrogen.  This will promote lots of healthy green growth above ground.

However, this can also cause the plant to neglect the production of potatoes, which is the part of the plant you want to eat!

For more information, check out my article on over fertilizing your plants, and my article on low nitrogen fertilizers.

If your potato plants get too tall, you have the option of staking them (just like tomato plants) to support them as they grow.

You can use stakes to support potato plants that are growing too tall and falling over.

tomato stake
You can use stakes to support potato plants that are growing too tall and falling over.

For more information, check out my article on how to support plants.

Temperatures Are Too Extreme For Your Potato Plant

If you can rule out over fertilization of your potato plants, then it is time to consider extreme temperatures.

Potato tubers (the part of the plant you eat!) form best at temperatures between 60 and 70 degrees Fahrenheit (16 to 21 degrees Celsius).

Potato tubers will fail to form at 80 degrees Fahrenheit (27 degrees Celsius) or above, so avoid planting them too late in the season, when they will encounter warmer soil temperatures.  It is best to plant potatoes as soon as the soil temperature gets up to 50 degrees Fahrenheit (10 degrees Celsius).

Potatoes can tolerate light spring frosts, but if temperatures get too far below 32 degrees Fahrenheit (0 degrees Celsius), the plant will die and fall over. If a fall frost threatens your potato plants, you can protect them with row covers by wrapping the whole plant down to the soil.

For more information, check out this article on potatoes from the University of Illinois Extension.

Improper Watering Of Your Potato Plant

If your plant has not encountered any frost or freezing, then it could be that improper watering is causing your plants to fall over.

garden hose
Be careful not to over water or under water your potato plants, or else you could kill them!

If you over water your potato plants, the soil becomes waterlogged, and the roots cannot properly absorb nutrients from the soil.  Eventually, the roots will rot, which will keep your plant from absorbing water.  This will soon kill your potato plant, causing it to fall over.

If you under water your potato plants, their leaves will sometimes curl as an early indication.  The best way to check whether your plant needs water is to feel the soil with your fingers.

If the soil is dry to a depth of a few inches, then it is time to water your plants.  When you do water your potato plants, water from below, to avoid wetting the leaves.

Also, water in the morning or at midday, to give any wet leaves time to dry out before nightfall.  Otherwise, you risk an increased chance of fungal diseases that affect potato plants.

Water deeply and infrequently, rather than providing a shallow amount of water on a frequent basis.  It is also recommended to avoid watering potato plants until after the plant emerges from the soil.

For more information on watering, check out this article on growing potatoes from the Oregon State University Extension.

Your Potato Plants Have A Disease

After ruling out over fertilization, extreme temperatures, and improper watering, we now need to consider the possibility that your potato plants are infected with a disease.

Unfortunately, there are many diseases that can affect potato plants and devastate your crop.  One such disease is blight, which comes in two types: early blight and late blight.

Your Potato Plant Has Early Blight

Early blight of potatoes is caused by a fungus, Alternaria solani, which spreads by spores on the wind, human contact, or by water splashing infected soil onto the lower leaves of a plant.

early blight on tomato leaf
Here, we can see symptoms of early blight: brown spots on leaves, with yellow around the spots.

Early blight will cause the leaves of potato plants to get brown spots will yellow rings on the outside of the spots.  This first occurs on the older (lower) leaves of the plant.

A severe infection can cause fewer and smaller potatoes growing on your plant.  It can also cause lesions on the potatoes themselves.

For more information on symptoms, check out this article on early blight of potatoes from the Michigan State University Extension.

Early blight will spread readily in damp conditions, with outbreaks often following extended periods of rainy weather.

The fungus that cause early blight can survive over the winter in the soil, infecting newly planted potato plants the following spring.  This is more likely to occur if you use compost that contains infected plants, and if the compost pile did not get hot enough to kill the fungus that causes early blight.

Early blight can also get into your garden if the seed potatoes you used were infected to begin with.  Make sure to order seed potatoes from a reputable seed company that guarantees their products!

Finally, remember that early blight also affects tomatoes, peppers, and eggplant.  So, an infection of any of these plants can also spread to your potato plants.  As a result, it is a good idea to practice crop rotation and avoid planting any of these plants in the same area in consecutive years.

Your Potato Has Late Blight

Late blight of potatoes is caused by a fungus, Phytophthora infestans, which spreads by spores on the wind.

potato late blight
This potato has been infected with late blight. I don’t want to eat that one!

Late blight is the more devastating of the two types of potato blight, able to spread rapidly and destroy entire crops.  In fact, late blight was responsible for the Irish Potato Famine of the 1840’s.

Late blight causes large, dark brown blotches on leaves and stems.  The disease spreads rapidly in damp weather at cool temperatures from 60 to 70 degrees Fahrenheit (16 to 21 degrees Celsius).

For more information, check out this article on late blight from the University of Minnesota Extension.

Late blight cannot survive in isolation in the soil.  However, it can survive over the winter in infected potato tubers.  As a result, you should remove any “volunteer” (unplanted) potato plants that grow in your garden, as a precaution against the spread of late blight.

Finally, remember that late blight can also infect tomatoes, and the disease can spread from your tomato plants to your potato plants.

Other Potato Diseases

Two other common diseases that can affect potato plants are fusarium wilt and verticillium wilt.  Your best bet is to purchase seed potatoes for varieties that are resistant to both of these diseases.

Disease resistance will often be denoted by an F (fusarium) and a V (verticillium) in seed catalogs or on company websites.

Pests Are Attacking Your Potato Plants

If no diseases seem to be present in your potatoes, then it is time to check for pests.  A couple of common pests that can cause problems for potato plants are cutworms and Colorado potato beetles.

Cutworms Are Attacking Your Potato Plants

Cutworms can completely cut off your potato plants at the stem, close to the ground.  If the potato plants that fall over are completely detached, then you likely have cutworms roaming in your garden.

cutworm
Cutworms will chew the stems of potato, tomato, and other plants. Is it possible for them to sever many plants in one night!

As any tomato or potato grower will tell you, a good way to prevent this cutworm damage is to use cutworm collars on your potato plants.

For more information on cutworm collars and other tricks, check out my article on how to get rid of cutworms using natural methods.

Colorado Potato Beetles Are Attacking Your Potato Plants

The Colorado potato beetle has an orange or yellow body, with black stripes running along its back.  They are about a quarter of an inch to half an inch in length.

potato beetle
Colorado potato beetles can multiply quickly and cause damage to your potato plants.

A single Colorado potato beetle can lay up to 500 eggs in a 5-week period.  These eggs are usually found on the underside of a leaf.

Colorado potato beetles are one of the biggest culprits in potato plant defoliation (eating and removal of the leaves).  If there is enough leaf damage, you could certainly see your plants falling over and dying before maturity.

Over the years, Colorado potato beetles have developed resistance to many pesticides.  Crop rotation is one way to prevent them from spreading.

Using straw as mulch for potato plants also helps to hide the potato plants, and encourages the potato beetle’s predators to protect your plants.

Conclusion

By now, you have a much better idea of why your potato plants are falling over.  Hopefully, it is due to the fact that your potatoes are mature and ready for harvest.

However, if that is not the case, then you know what other problems to look for, and how to prevent these issues from hurting or killing your potato plants.

I hope you found this article helpful – if so, please share it with someone who can use the information.  If you have any questions or advice about potato plants falling over, please leave a comment below.

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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