Where I live in Wisconsin, there’s lots of garden lore around when you should plant potatoes – on St. Patrick’s Day, when you see the first crocus, the first day of Lent, or as early as possible after the ground thaws.
All of these times are very early in the gardening season. And it’s true, you can plant potatoes in early spring. But, if you missed that window, don’t worry, there’s still time. In this article, we’ll be answer the key question: how late can you plant potatoes?
We all love potatoes (fried! mashed! twice baked!) and there are a lot of good reasons to grow and eat them. Luckily, there is some flexibility in when they can be planted during the season.
Best Time to Plant Potatoes: Factors to Consider
Potatoes are delicious, versatile, and chock full of vitamins and minerals, including Vitamin C and potassium. They’re not difficult to grow, so you don’t need a green thumb or a lifetime of experience for an abundant potato harvest.
For various reasons, you may decide you want to plant your potatoes on the later side this season. How late you can do that depends on where you live, when you want to harvest, and the type of potatoes you’re growing.
But first, if you’re planting your potatoes at the beginning of the gardening season, there are two important factors to consider.
Potatoes are a cool weather crop.
They grow well in spring temperatures and can tolerate some frost. Because of this you can plant them about four weeks before the last anticipated frost date. Depending on where you live, this could be as early as Valentine’s Day or as late as April or May. I usually plant mine in mid- to late April depending on the weather.
But, even though they’re frost tolerant, potato plants can be damaged if you get a hard frost. Luckily, it takes a while for the potato tubers to sprout, so you can plant them early and know that you have a couple weeks until the plant breaks the surface of the soil.
Potato seeds rot easily.
One of the dangers of planting your potatoes as early as possible in spring is that the soil is more likely to be wet and cold. This can cause the potato seeds to rot, which will result in no potatoes! If you live in an area with lots of rain and cool weather in spring, I recommend pushing your planting date a little later until the soil dries out and warms up.
All gardeners know that things don’t always go as planned, and spring weather can be very fickle. What happens if there’s a cold, wet spring that makes it impossible to put potatoes into the ground early?
Don’t despair. You still have some options.
How Late Can You Plant Potatoes?
If you’re planting potatoes outside of the early spring season, the answer to this question really depends upon where your garden is located and a few additional things to consider.
The number of days to harvest
When you’re planning out a late planting, be mindful that it takes at least 90 days up to 120 days, depending on the variety, for potatoes to reach maturity. After we pass the summer solstice, the days start becoming shorter. As we near the fall, plant growth slows down. If you’re planting in late summer or early fall, know that it will take much longer for the plants to produce a harvest due to the fewer hours of daylight.
Soil temperature
As we discussed above, potatoes can grow well throughout the summer, especially in cooler climates, but if the soil temperature rises above 75 degrees, the plants can stop producing tubers.
Average first frost
If you live in an area that receives hard frosts, the plants will not survive those cold temperatures, so you’ll need to make sure they’re done producing potatoes and out of the garden before this time. For late plantings, you’ll want to plant your potatoes at least 110 days before your average first frost.
Throughout North America there are many different zones and climates where gardeners are located. This means there’s not one answer to the question how late can you plant potatoes.
Let’s talk about some different locations as examples:
- If you live in a colder northern climate like I do, zone 5a, you can safely plant potatoes into June and you’ll get a fall harvest, especially if you follow the summer tips below.
- If you live in a hot climate like Texas or Florida, you can plant potatoes in mid-August.
- If you live in a hot desert climate like Arizona, you can wait and plant potatoes in September as the weather cools down and heads into fall.
Overall, I suggest looking at your local extension website for recommended planting dates and talking to gardening friends in your area to pin down the best time for a late planting in your area.
If you end up planting potatoes later in the season or you live in a hot climate, there are two important things you can do to encourage a healthy harvest.
Mulch your potatoes.
Most gardeners use the hilling technique when growing potatoes. Eventually, you run out of soil to hill around the plants. This is a great time to spread a thick layer of mulch around your potatoes. I prefer weed free marsh hay or straw. Mulch will keep the soil cool throughout the warmer months and help prevent slowed production from high soil temperatures.
Water your potatoes.
In order to encourage robust production, keep your potato plants well watered. Potatoes like consistent moisture throughout the plant and tuber growth period. But, they don’t like to grow in soggy or extremely dry soil, so watering is a balancing act. This is an important factor in having a successful harvest, so I wrote a thorough article about watering potatoes
Now that you’re more clear on how late can you plant potatoes for a successful harvest it’s important to also know more about their preferred growing conditions, how deep to plant them, and how far apart to space them.
How Much Sun Do Potatoes Need?
Potatoes do best in full sun, and some varieties, including most white potatoes and sweet potatoes, prefer at least eight hours of sun per day to reach maximum productivity.
They can, however, produce plenty of flavorful potatoes with only six hours of sun per day. Red potatoes in particular can thrive with less than eight hours.
Giving potatoes the ideal amount of sunlight can be complicated if you planted them very early spring or into the fall when the days are short and shadows from nearby buildings and trees are long. So, plan carefully and try to plant in an area that will as much sun as possible each day as the season progresses.
It is possible to grow some potatoes, including red potatoes, in part-shade as long as they’re well-nourished. Potatoes need fertile soil that’s rich in potassium and phosphorous. I recommend using an organic garden fertilizer when you plant.
You can also grow potatoes in containers that can be moved around the yard to take advantage of available sunlight, but many gardeners report lower yields when not growing potatoes in the ground.
How Long Does It Take To Grow a Potato?
Generally, it takes between 90-120 days to grow potatoes, but the length of time it takes for the tubers to fully develop depends on the variety.
It’s best to research carefully and be familiar with the growing requirements before you plant. Also consider your own personal preferences and the length of your cool weather growing season. This Potato Varieties Comparison Chart from Johnny’s Selected Seeds offers a convenient breakdown of 15 different varieties.
New potatoes can often be harvested within 60 days. If you’re time-challenged or you, like me, just like your potatoes young and tender, you don’t need as much growing time as you would if you were growing more mature potatoes.
How long it will take the potatoes you plant to mature will affect the answer to the question – how late can you plant potatoes?
How Deep Do You Plant Potatoes?
Several days before planting, you should prepare your seed potatoes. If you’re planting larger potatoes, cut them into pieces with at least two eyes per section. Make sure the sections aren’t too small or they may rot. Lay them out in a single layer in your house or garden shed so the cut areas dry out, or “scab over”. This will help preventing rotting.
Most gardeners use a trench method to grow potatoes. Trenches should be 30-36 inches apart and 6-12 inches deep to allow potatoes plenty of room to grow. Potatoes are heavy feeders, so mix some organic garden fertilizer into the soil before planting.
Place each piece cut-side down into the trench, 10-12 inches apart. Cover with about four inches of soil. Leave the rest of the soil to the sides of the trenches to use for hilling as the plants grow.
As the plants emerge and grow, hill them by raking or shoveling the mounds of soil outside the trenches around the plants. Keep mounding until you run out of soil.
Potato tubers develop best in a dark environment, so make sure the plant’s roots get as little sunlight as possible.
After you complete the mounding process, spread a thick layer of vegetable garden mulch around the plants to retain soil moisture and keep the soil cool.
Learn about watering potatoes so that your roots don’t rot or suffer from too little moisture.
Potato Spacing
If you’ve never grown potatoes before, you might also have questions about how far apart to space the plants. Place each piece of potato about 10-12 inches apart, in rows are about 30-36 inches apart.
If you’re planting smaller varieties, including Yukon Gold and Fingerling, you might be able to plant them a little more closely, but don’t try to cram too many potatoes into too small a space.
Planting too closely could stunt the plant’s growth and prevent them from reaching their maximum potential.
Growing potatoes successfully doesn’t require extraordinary skill or experience, just some knowledge about what helps them thrive. This season, even if you’re a beginner gardener, you can harvest an abundance of delectable potatoes for summer picnic potato salads or fall mashed potatoes!
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