When Is It Too Late To Plant Potatoes? (3 Things You Should Know)


If this is your first year planting potatoes, or if you got a late start on your garden, you might be wondering if the time for planting potatoes has passed.  After all, you don’t want to put in the effort to plant a crop of potatoes that won’t grow well.

So, when is it too late to plant potatoes?  Most gardeners should plant potatoes by the end of May for spring planting. This allows enough time for the plants to grow & mature before cool weather (and frost) in fall. Plant before soil temperatures reach 80 degrees Fahrenheit (27 degrees Celsius), since tubers will stop forming if it is too warm.

Of course, if you live in a very warm climate, you may be able to plant mid-season and late season potato varieties in July or even August to get a second harvest later in the year.

If you live in a cold climate, you can extend the growing season with greenhouse, row covers, or mulch to protect against frost at the end of the season.

In this article, we’ll take a look at the many factors that determine when you can plant potatoes, including frost dates or the type of potato and its time to maturity.

Let’s get started.

When Is It Too Late To Plant Potatoes?

To determine when it is too late to plant potatoes, there are 3 main factors to consider:

  • 1. Variety of Potato (determines the number of days from planting to maturity)
  • 2. Last Frost Date (cold temperatures in the fall will kill potato plants)
  • 3. Desired Harvest (new potatoes, mature potatoes, large potatoes)
sprouting potatoes
Usually, you plant pieces of sprouted potatoes (seed potatoes) in the spring. Some varieties mature much faster than others.

Let’s start by looking at the different types of potatoes you can choose to grow.

Variety

The variety of potato you choose will play a big part in determining when to plant your crop.  The variety you choose will determine the time to maturity for your potato plants.

The time to maturity (or days to maturity) is the number of days it takes for a potato plant to grow into a mature plant and produce tubers that you can harvest.

According to Fedco Seeds, potatoes can be classified in 3 different groups, depending on the time to maturity:

Baby Potato Plant
Some potato varieties mature in as little as 60 days, while others take up to 110 days to mature.

According to the University of Illinois Extension, you can plant any of the three (early season, mid-season, and late season) types of potatoes in the spring.

Avoid planting potatoes when the ground is still wet from heavy spring rains.  Otherwise, they may rot before they can sprout and grow!

Planting too early in the spring may also expose your potato plants to frost, which can kill them or set them back (more on this later).

You can plant some potato varieties as late as July 1stas long as you live in a mild climate.  If you want to store your potatoes over the winter, late season potatoes are the best option (since harvest comes closer to winter).

Frost Dates

The first frost date in the fall will also help to tell you if it is too late in the season to plant your potatoes.  There is a 30% chance that no frost will occur before the first frost date (or first fall frost date).

frosted leaf
Frost is a problem for potato plants, since it can kill back all of the growth above ground.

For example, in Boston, MA, the first fall frost date is November 3.  This means that there is a 30% chance of getting at least one frost on or before November 3.  It also means that there is a 70% chance that no frost will occur before November 3.

Last frost dates will vary widely depending on where you live.  For example, the last frost date in Montpelier, Vermont is September 24, while the last frost date in Atlanta, Georgia is November 13.  In Miami, Florida, frost is very rare, and may not occur for years on end.

Before you decide whether it is too late to plant potatoes, use this tool from the Old Farmer’s Almanac to find the last fall frost date in your area.

Desired Harvest

Depending on the size of potatoes you want at harvest, you might be able to get away with planting a little bit later in the year.

New Potatoes

If you are hoping for new potatoes (small, less mature potatoes with thin skins), then you can harvest them 2 to 3 weeks after the plant stops flowering.  Not all potato plants will flower, so you may need to dig in the ground every once in a while to see how they are growing.

small potatoes new potatoes
New potatoes are small, with thin skins. The advantage is that they are ready early in the season.

According to the University of Maryland, you can harvest new potatoes 6 to 8 weeks (42 to 56 days) after planting.

Mature Potatoes

Mature, full-size potatoes have thicker skins, and they take longer to grow than new potatoes.  Basically, you let new potatoes grow for a bit longer so they can mature fully and get bigger.

potatoes in basket
Mature potatoes are larger than new potatoes, but they take longer to grow.

Mature potatoes will be ready for harvest 2 to 3 weeks after the foliage on the plant dies back.  If you plant late in the season, there will be less time for the potatoes to grow.  As a result, you will get smaller potatoes on each plant and fewer potatoes in total.

Summer heat with soil temperatures over 80 degrees Fahrenheit (27 degrees Celsius) will stop tubers from forming.  On the other hand, fall frosts will kill the plant and stop growth.

Can You Still Plant Potatoes In July?

You might be able to plant potatoes in July if you live in a warm climate and you choose potato varieties that don’t take too long to mature.

For example, if you live in Boston, Massachusetts, your first frost date is November 3. If you choose Red Pontiac potatoes (a mid-season variety), they will be ready for harvest about 80 days (11.5 weeks) after planting.

Working backwards, you could plant in July and still get potatoes by November 3 (31 days in August + 30 days in September + 31 days in October + the first 3 days in November = 95 days).

Can You Still Plant Potatoes In August?

You might be able to plant potatoes in August if you live in a very warm climate and you choose fast-maturing potato varieties.

For example, if you live in Atlanta, Georgia, your first frost date is November 13. If you choose Red Norland potatoes (an early season variety), they will be ready for harvest about 70 days (10 weeks) after planting.

That means you could plant in August and still get potatoes by November 13 (30 days in September + 31 days in October + the first 13 days in November = 74 days).

Can You Plant Potatoes In The Fall For Next Year?

If you plant potatoes in the fall (or leave them underground without harvesting them), there is a chance that they will sprout and grow into new plants the following spring. However, the longer potatoes stay underground, the more chance that they will rot or that pests (animal or insect) will eat them.

potato plants in container
If you don’t dig up potato tubers, they might survive the winter and sprout the following spring to produce new plants.

Your best bet is to harvest and store your potatoes and wait to plant sprouted potatoes in the following spring.

Can Potatoes Grow In Winter?

Potatoes can grow in winter in very warm climates. However, a frost will kill the foliage back to the ground.

Your best bet is to grow potatoes by planting in spring (or early to mid summer for a 2nd later harvest in warmer climates).

When To Start Your Potato Plants

You can use the factors mentioned above to figure out when it might be too late to plant your potatoes.  For example, let’s assume that:

  • you live in Boston, MA
  • you want to plant a late-season potato variety, such as Princess Laratte
  • you want to harvest mature potatoes (not new potatoes)

We know that the last frost date in Boston is April 10.  We also know that Princess Laratte potatoes take 90 to 110 days to mature.

calendar
You can calculate whether potatoes will mature in time by using your calendar, planting date, first frost date, and the days to maturity for your chosen potato variety.

Let’s say that we are planting a week late to reduce the chance that a late spring frost will kill our potato plants when they emerge. So, we wait until April 17 to plant our potatoes.

Working forwards from April 17, we can see that the potatoes would be mature on July 16 at the earliest (13 days in April + 31 days in May + 30 days in June + the first 16 days in July, for a total of 90 days).

For a spring planting, you can plant potatoes as soon as ground can be worked (that is, when it thaws out).  However, remember that potatoes will not grow until the ground is at least 45 to 50 degrees Fahrenheit (7 to 10 degrees Celsius).

When planting potatoes, the soil should be moist, but not wet.  Wet soil will cause potatoes to rot before they can grow.

According to the Old Farmer’s Almanac, you can take a chance and plant potatoes 6 to 8 weeks before the last spring frost date in northern regions.  These crops will mature earlier in the season, but there is more risk of late spring frosts damaging or killing the plants when they emerge.

Especially in cold northern regions, it is safer to plant your potatoes any time in the week or two before the last frost date.

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

grow your own potatoes sidebar
If your potatoes sprout in long-term storage, you can replant them to grow new plants and more potatoes!

How To Protect Potato Plants From Cold

Potato plants are a cool weather crop, so they can tolerate some cool temperatures.  However, a hard frost can kill back any growth to the ground, so it pays to protect them if possible.

In case of a late spring frost or early fall frost, here are a couple of ways you can protect your potato plants from cold.

Greenhouse

The soil in a greenhouse will get warm enough for planting potatoes much sooner than the soil outside.  You also have more control over the soil moisture inside your greenhouse.

You can even choose to plant potatoes in containers inside your greenhouse if you wish (you can also try planting potatoes in a straw bale!)  For more information on growing potatoes in straw bales, you can read my article here.

greenhouse
A greenhouse will help to keep your potato plants warm and protect them from fall or spring frosts.

If you plant your potatoes a little late, you can use a greenhouse to extend the growing season and protect your potato plants from fall frosts.

Row Covers

You also have the option of using row covers to protect potato plants against late spring or early fall frosts.  Row covers are made from fabric, and they protect plants from cold (and insects), while also allowing sunlight to get through.

row cover
Row covers can help to keep potato plants warm. if the plants are young, you can use a long piece to cover an entire row of potato plants.

One brand of row cover with varying levels of protection is Agribon.  For example, Agribon AG-50 offers 6 degrees of frost protection (down to 26 degrees Fahrenheit).

You can learn more about row covers in my article here.

Mulch

Mulch is another great way to keep potato plants a little warmer. Even if a frost comes, a layer of mulch hilled up around a potato plant will protect part of the plant.

Even better, hilling during the growing season is encouraged for potato plants, and it won’t hurt them. You can learn more about hilling potatoes (and why to do it) in my article here.

You can use lots of materials for mulching and hilling around your potato plants. Some common ones include:

  • Straw
  • Grass clippings
  • Leaves
  • Compost
straw
Straw is a great choice for hilling around potato plants. Grass clippings, leaves, and compost also work.

All of these materials will eventually decompose, adding both nutrients and organic matter to your garden.

What Happens If You Plant Potatoes Too Late?

If you plant your potatoes too late, you will have problems with heat in the summer or with cold in the fall.

Summer Heat

The first problem you will have with a spring planting of potatoes is the summer heat.  Potato plants will stop producing tubers if the soil is too warm.

potato plants
Potato plants will stop producing tubers if temperatures get too high.

Higher temperatures and brighter sunlight also cause soil to dry out faster.  Remember that young potato plants are not yet established with strong roots.

That means you will need to work harder to give them enough water.  This can be a big chore in a large garden, especially without drip irrigation or a sprinkler system for watering.

Fall Frost

Even if you manage to deal with the summer heat by planting later in the season, you still need to worry about frost in the fall.

frost
A hard frost will kill potato plants (at least, the part growing above the ground).

A hard frost will kill potato plants, and an early fall frost will stop the plants from growing larger tubers.  If the ground freezes, it will be difficult to harvest your potatoes without damaging them (if you can get them at all!)

Conclusion

Now you have a better idea of when it is getting too late to plant potatoes – and when you might be able to plant for a later harvest.  You also know a little more about how to protect your potato plants from frost, if necessary.

If you are in a warm climate or you have space indoors, you can learn more about growing potatoes in winter in my article here.

grow your own potatoes sidebar

I hope you found this article helpful – if so, please share it with someone who will find the information useful.

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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