Do You Need To Hill Potatoes? (4 Reasons You Should)


Hilling potatoes adds a lot of work to the process of growing.  There are some benefits to hilling, but they need to justify the extra effort that is involved.

So, do you need to hill potatoes?  Potato plants will still grow without hilling.  However, hilling potatoes has several benefits.  It provides stability as the plant grows taller, controls weeds near the plant, and protects the plant from frost.  Hilling also prevents green potatoes by keeping the tubers out of sunlight.

Of course, you don’t need to hill potatoes with soil – there are lots of other materials you can use, including straw and mulch.

In this article, we’ll talk about some of the benefits of hilling potatoes.  We’ll also look at how to do it and what you can use as an alternative to soil.

Let’s dig in.

Do You Need To Hill Potatoes?

Technically, you do not need to hill potatoes (also called mounding or earthing up).  Potato plants will still grow without hilling up the soil around them.

rows of potatoes
Hilling potatoes is not necessary, but it will improve your yield and avoid green tubers.

However, you will get better results if you hill your potatoes.  The main benefits of hilling potatoes are:

  • Provides stability as plants grow taller (that way, you won’t have to use stakes or cages to keep them from falling over).
  • Controls weeds (adding soil around the base of the plant will smother existing weeds and make it harder for new ones to get started).
  • Frost protection (a hard frost in spring may kill the part of the potato plant above ground, but the parts below ground are more likely to survive).
  • Prevents green potatoes (not only are green potatoes unsightly, but they likely contain solanine, which is toxic to humans.  Potatoes turn green when exposed to sunlight – you can learn more about why it happens in my article here).
frosted leaf
Hilling potatoes will protect part of the plant from frost damage in the spring.

What Happens If You Don’t Hill Potatoes?

If you don’t hill your potatoes, you are more likely to end up with green tubers.  This happens when potatoes are exposed to sunlight.

green sprouted potato
This potato has been exposed to sunlight and turned green as a result.
Image courtesy of:
Wikimedia Commons: https://commons.
wikimedia.org/wiki/File:Evil_green_potato.jpg

Potatoes that grow near the surface of the soil are more likely to be exposed to sunlight.  Larger potatoes are more likely to pop up above the soil surface.

Soil erosion can also contribute to this problem.  You can learn more about how to prevent soil erosion in my article here.

Without hilling, potatoes are more likely to succumb to a spring frost.  They also face increased competition from weeds.

Does Hilling Potatoes Increase Yield?

Hilling potatoes increases yield by giving you healthier plants.  Stronger plants with more energy will be able to produce larger tubers.

As mentioned earlier, hilling controls weeds so that potato plants don’t have to compete with them for water and nutrients.  This results in more vigorous plants.

weeds
Hilling potatoes will smother weeds around the base of the plants, reducing competition for water and nutrients.

Hilling also provides frost protection.  This prevents your potato plants from suffering a setback in the spring.

If you use straw (or other types of mulch) for hilling, it will retain moisture in the soil.  This will prevent drought and lead to a better potato yield at harvest time.

How To Hill Potatoes

After planting and burying seed potato pieces in a trench (with proper spacing), green growth will emerge above the soil.  After this happens, it will soon be time to hill your potato plants.

To hill potato plants, all you really need to do is pile up soil around the base of each plant (there are other materials you can use – more on this later).  Adding a few inches of soil at a time will suffice.

potato plants
After potato plants are 6 to 12 inches tall above the soil, it is time to hill them for the first time this season.

Remember that you don’t want to bury the entire plant (it’s called hilling, not burying!)  According to the Oregon State University Extension, you should avoid covering the leaves when hilling potatoes.

The leaves above ground need sunlight to produce energy (by photosynthesis).

When To Hill Potatoes

Hill potatoes when the part of the plant above ground is 6 to 12 inches (15 to 30 centimeters) tall.  The plant will continue to grow after the first hilling, and you will need to pile up more soil during the season.

You can use height as one indication of when to hill potatoes.  After each hilling, wait until the plant grows 4 to 8 inches taller before adding 2 to 4 inches of soil to the mound at the base of the plant.

potato plants
When potato plants are 6 to 12 inches tall, you can hill them for the first time.

You can also use the appearance of weeds to time the hilling of your potatoes.  When small weeds start to appear (but before they are well-established), add some more soil to the mound to smother the new weeds.

If a late spring frost threatens, it may make sense to hill up the potatoes the night before (since the frost may kill the part of the plant above ground).  You also have several options to protect your plant from cold – you can learn more here.

How Many Times Do You Hill Potatoes?

According to the University of Maine Extension, potatoes may need hilling 2 or 3 times during the season: the initial hilling at 6 to 12 inches tall, followed by 1 or 2 additional times later in the season.

baby potato plant
This baby potato plant is not quite ready for hilling yet – but it will be ready soon!

If your plants really take off (or if you want to add a smaller amount of soil at more frequent intervals), you might end up hilling 4 or 5 times.  This may be helpful to smother new weeds at regular intervals.

How High Do You Hill Potatoes?

According to the University of Minnesota Extension, hilling will result in mounds of soil that are 6 to 8 inches tall by the end of the season.

potato plants in container
You should hill potatoes whether they grow in the ground or in a container.

With 2 to 3 hillings per season, this means that you will be adding 2 to 4 inches of soil to the mound each time you do it.

When To Stop Hilling Potatoes

You can use the height of the soil mound to tell you when to stop hilling.  If the mound is 8 inches high, that is probably sufficient for your potato plants to avoid green potatoes.

You can also use flowers to tell you when to stop hilling.  According to the Oregon State University Extension, you should stop hilling soon after flowers appear on your potato plant.

potato flowers
You can stop hilling potato plants shortly after flowers start to appear.

If your potato plants start to turn yellow and fall over, that usually means the end of the season is close.  At that point, hilling won’t really help (and it will add more work to find the underground tubers at harvest time).

You can learn about ways to dig potatoes in my article here.

What To Use To Hill Potatoes

There are lots of materials you can use to hill potatoes besides soil, including:

  • Straw – a layer of straw keeps soil cooler and prevents water loss through evaporation.  When thick enough, straw can also block sunlight to prevent potatoes from turning green, bitter, and toxic.
  • Grass clippings – grass clippings are easy to find, but make sure to source it from lawns grown without pesticides or herbicides.  Otherwise, beneficial insects (and the potato plants themselves) may suffer the consequences.
  • Wood chips – wood chips are what we often think of when we hear the word “mulch”.  Wood chips are more often used in landscaping for the sake of appearance, but they could form a layer for hilling potatoes in a pinch.
  • Peat mosssphagnum peat moss absorbs lots of water (up to 10 times its weight).  If you put a thick layer over your soil, it might prevent water from reaching your potato plants.  In this scenario, consider using drip irrigation to water your plants and put the peat moss over it to keep the tubers from turning green.
  • Hayhay tends to contain the seeds of weeds (unlike straw), so it might not be a great option for hilling potatoes if you want to reduce the work of weeding.  Of course, it will work in a pinch if you have nothing else available.
  • Compostcompost will work perfectly in place of soil to hill potatoes.  The best part is that you can just mix it into the soil at the end of the season to replace nutrients and organic matter and improve overall soil health.
compost bin
You can hill potatoes with compost as one alternative to ordinary garden soil.

Hilling Potatoes With Straw

Growing potatoes by hilling with straw is a method used by gardeners who want the finest potatoes for competitions.  According to the University of Illinois Extension, potatoes grown with straw hilling tend to have better size, color, shape, and smoothness than potatoes grown in soil.

straw
Using straw to hill potatoes can give you tubers with better size, color, shape, and smoothness than ones hilled with soil.

Instead of burying the seed potato pieces in a trench, they are planted right at the soil line (on the surface).  The seed potatoes are then covered with 4 to 6 inches of straw.

After a short time, the seed potatoes will sprout and green growth will come up through the straw.  If the straw rots away (more likely in wet and humid climates), simply add another layer to keep the tubers out of sunlight.

Straw keeps the soil up to 10 degrees Fahrenheit cooler and prevents water loss by evaporation.  It can also provide a little extra insulation if cold threatens your plants in the spring.

At the end of the season, you won’t have to dig through soil to find the potato tubers.  All you will need to do is remove the straw (probably well-rotted by now) to get the potatoes.

large and small potatoes
With proper hilling, you can get a nice little harvest of potatoes at the end of the season.

Conclusion

Now you know why it is a good idea to hill potatoes.  You also know how to do it and what you can use (besides soil).

Potato plants can tolerate partial shade, but need some sun – you can learn more about sund and shade for potato plant in my article here.

You can learn how to plant sprouted potatoes in my article here.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

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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