It’s safe to say that growers love to watch their crops grow. We wait patiently for each sprout to mature and produce perfectly ripe fruit or vegetables. But when it comes to root vegetables, we can’t just watch and wait. We have to time the harvest just right. Pull your produce too early, and you’re stuck with unripe, tiny veggies. Wait too long and you take a risk of the crop being overripe – or even beginning to rot underground.
How long do potatoes take to grow?
Many things influence how long potatoes take to grow. Variables such as the potato variety, climate, seed preparation, and amount of fertilizer all play a part. Taking all these things into account, the average length of the growing season for potatoes is between 90 to 120 days, or 3 to 4 months.
The following factors all have their part to play in how it takes potatoes to grow
- Choosing early, mid-season, or maincrop varieties
- The climate of your country
- Seed preparations such as chitting
- Potato planting date
- Desired size at harvest
Choosing early, mid-season, or maincrop varieties
There are three main types of potato varieties and, while some are ready in just under 3 months, some take an extra month to mature. Early varieties or new potatoes will be harvested earlier in the year than maincrop.
Early varieties do not necessarily mean they grow faster – just that they are ready earlier in the year. The same goes for mid-season and maincrop. All potatoes take roughly the same amount of time to grow it’s just that their planting dates determine the time of year they are ready to harvest.
Earlies
Early potatoes planted in mid-February may only be ready by the middle of July which is around 112 days. It may be possible to harvest at 100 days in warmer climates or if they grow really well.
You can start harvesting them as soon as the first large tubers appear – these tender young spuds can be very tasty. Their thin skin means the potatoes need to be eaten within a few days or they will spoil.
Mid-season
Usually, mid-season potatoes are planted in mid-March and ready by August again around 120 days. A mid-season potato is deemed mid-season as this is the optimum time of year the variety has been bred to grow.
Maincrop
Maincrop or late-season potatoes take between 100 to 120 days to grow and mature. They are usually the highest-yielding potato varieties and are designed to grow to full maturity and have thick skin for long-term storage.
Maincrop potatoes are bred to mature later in the year so they are harvested in colder weather, enabling farmers to use the colder months to store them well.
The climate of your country
The first thing you’ll need to consider is your local climate. Potatoes don’t like very warm weather. This means that you can begin planting as soon as the danger of frost has passed and you’re able to work the soil.
In more Northern regions, it can be a gamble to plant early potatoes earlier than March. But you can cover young shoots with plastic containers, burlap sheeting, or mulch overnight to protect them from late frosts.
Temperature
On the other hand, if you live in a very hot climate, you may need to plant earlier – like in December or January. You may need to avoid the extreme heat of summer – it can wreak havoc on your crop.
Closer to the Equator, potatoes are even grown as a winter crop and you may be planting in November or December.
It’s really all about the soil – we need both the right temperature and humidity levels.
At planting the soil temperature should be at least 10°C (50°F). It should also be dry enough not to stick together – not only will clumpy soil be hard to plant in, but seed potatoes can rot if the soil is too wet.
Sunlight
Your potatoes will grow best in a sunny location with cool, loose, well-drained soil. The ideal temperature range is 16 to 20 degrees Celcius. Plant your potatoes away from high trees or hedges which prevent sunlight from getting to the plants.
Rainfall
If your climate has low rainfall, you will most likely need to water your potato crop. Growing potatoes require at least an inch of rain a week to grow well.
Do all potato varieties take the same time to grow? More or less. Most potatoes can be harvested between 90 and 110 days after planting.
Seed preparations such as chitting
If planting earlies, you should prepare your seed potatoes ahead of planting by “chitting” them. Find a warm frost-free place that is quite dark. Stand your seed potatoes in an egg carton or seedling tray with the rose end (where you see the most eyes, or small dents) pointing up.
When the shoots are about 2 cm (1”) long, prepare them for planting, by bringing them into the daylight where the buds will go from white and brittle to soft and green – perfect for planting with.
This method can also be useful for maincrop potatoes. You can begin the process indoors while there is still frost in the garden. This lets you get a jumpstart on the growing season.
Potato planting date
Planting time varies, depending on your location and the type of potato you’re growing. In colder regions, you’ll want to plant slightly later, and in warmer climates, you can plant a little earlier. If growing in containers, then you can also plant anytime as you will be indoors.
As a general rule, early potatoes should be planted by March. Mid-season varieties are typically planted by April and maincrop late-season potatoes by the end of May.
While healthy potato plants can tolerate light frosts or even a mild freeze, they can’t survive hard freezes. Potatoes should be planted in cool weather – after the danger of freezing has passed, but well before hot weather sets in for the summer.
Potato size at harvesting
Early potatoes are harvested from late June onwards and maincrop potatoes are harvested from September onwards.
A good rule of thumb is 100-120 days after planting. You can also watch your potato plants for signs that your crop is ready to harvest.
You can begin to harvest earlier if you prefer smaller potatoes or you can leave them in the soil for longer if you prefer larger potatoes.
You can check for new potatoes a few weeks after the plants have finished flowering. With their thin skins, these baby potatoes won’t be cured or stored, so only pull enough for 2-3 days, and be sure to store them somewhere cool.
When the foliage begins to yellow and die back, your potatoes will be almost ready. You can stop watering your crop at this point, and when the plant tops have completely died, you can begin to harvest the potatoes.
When growing with optimum fertilizer rates, your potatoes may begin to get too big. You may need to stop the crop growing by spraying with a crop desiccant or cut the tops down to soil level.
Digging your potatoes
Start by digging up a test hill to determine if your potatoes are mature enough to harvest. The skins of mature potatoes are thick and firmly attached to the flesh. If the skins are thin and rub off easily, your potatoes should be left in the ground for a few more days if you intend to store them
Remember that although potatoes can tolerate a light frost, you will need to dig them out before the first hard frost is expected. You shouldn’t wash newly dug potatoes – the freshly harvested tubers need time to cure and for the skins to dry before they can be stored.
You can cure your crop by arranging the potatoes to have good airflow through them and allowing them to sit at room temperature for about two weeks. Once cured, the potatoes can be stored in a cool, dark place for 6 months or more.
Factors affecting maturity
- As mentioned earlier, chitting or pre-sprouting your potatoes will help cut the outdoor growing time by at least a couple of weeks.
- Covering your young potatoes at planting can help them become established as well as protect them from late frosts. You can use plastic containers, mulch, or even an old blanket. Leaving your potatoes vulnerable to frost can definitely lengthen maturation times, and also puts them at risk of dying.
- Using fertilizer will also help your plants grow well and increase their yield. You should add a suitable potato fertiliser when planting your seed potatoes. If you feel they are lacking in size later in the year – say at flowering – you can add more if you feel they need it. The fertiliser can be homemade fertiliser or bought in.
- A note about adding a large amount of fertiliser is that it can extend the growing season of the potato. So although your potatoes will be bigger, they can take longer to mature.
Summary
Before you put any potatoes in the ground you should have the season ahead planned from planting to harvest. You should know the type of potatoes, if they’ll be chitted, when they should be planted, how much fertilizer you’ll use, and when they should be ready to harvest. Salad or baby potatoes will take the shortest length of time to grow at around 80 days, then early and mid-season varieties at 90 to 100 days, and finally maincrop potatoes which can take 100 to 120 days on average. Good luck!
