The perfect time to harvest potatoes – and how to do it

Growing and harvesting potatoes is relatively simple, although it can be difficult to know when to harvest them as they are hidden below ground. The right time to harvest will also depend on the variety you are growing and when you planted them. The weather conditions during their growing season and where you live in the country will also play a part. 

There are two main types of potatoes: early potatoes and maincrop potatoes.  

Early potatoes, or new potatoes, are sweet and tender spuds with thin skins. They need less time from planting to harvest than maincrop potatoes, requiring as little as 12 weeks, and are ready to harvest in June. There are two types of early potatoes – first earlies and second earlies.  

Maincrop potatoes produce larger potatoes, which are perfect for roasting and baking, need longer in the ground and are ready to harvest in late summer and early autumn.  

Although we can get a good indication of when potatoes are ready to harvest by doing some simple maths – adding their growth time onto the date they were planted to get an indication of when they will be ready – there are a few visual signs that indicate when it’s time to unearth your home-grown offerings.  

“The plants will begin to go yellow and start to die back,” says Chris Brock, senior gardener at the National Trust’s Gibside, “and from this point you know they’re not going to grow anymore.”  

Although, he does point out, when you harvest depends on how patient you are. “You can start harvesting first earlies in June, but if you wait a couple of weeks, they’ll be slightly bigger,” he says. 

Flower growth can also indicate that the potatoes are ready to harvest, although Brock advises this depends on the variety. 

If you’re checking to see if your potatoes grown in the ground are ready to harvest, Brock suggests picking out one plant to inspect. 

“Work with a fork about 30cm (1ft) away from the plant,” he says. “Have a rootle around without disturbing the plant too much and carefully remove the soil to find the potatoes. You’ll then be able to see if they are ready to harvest or not.” 

It’s harder to check if container-grown potatoes are ready without upending the pot, so in this instance, it’s best to rely on the visual signs unless you can move back the soil and see any tubers.   

For no-dig potatoes, simply remove some of the mulch to check if the potatoes are ready.  

How you harvest your potatoes will depend on how they are planted, whether they are in the ground, in containers or grown using the no-dig method. 

Open ground potatoes

For potatoes grown in the ground, place a garden fork at least 30cm (1ft), as above, and carefully work the fork towards the plant. You can then unearth the tubers, being careful not to spike them with the fork’s prongs.   

If you don’t have a garden fork, you could use a spade, but Brock warns you to be extra careful: “Using a spade makes it harder to feel around the ground and you’re more likely to slice through the tubers.” 

However, if you do spike your potatoes, Booth says it’s not a disaster: “It just means you won’t be able to store them. They’ll need washing and eating on the same day.” 

Container potatoes

Potatoes grown in containers can be upended once the plant has finished flowering. The potatoes can then be harvested with ease. 

No-dig potatoes

If you’ve grown your potatoes using the no-dig method, where the seed potatoes are placed on top of the soil and covered in a mulch of compost, straw or hay, the potatoes can be harvested by simply pushing back the mulch with your hands. 

Unlike early potatoes that can’t be stored, maincrop potatoes need a little more attention to get them ready to store.  

“Once you’ve dug them up, knock off any soil,” advises Brock, “then leave the potatoes in the sun for long enough to allow them to dry. Then store them somewhere cool and dark, and they should last for months and months.” 

Brocks says that one problem to watch out for is late frosts, which can occur until the end of May: “By this time the plants are already sprouting and if they are exposed to frost they will get damaged.”  

He advises: “The best prevention is to ‘earth up’ around the plants, or put some fleece over them, and if they are in containers, you could bring them indoors.” 

Late potato blight attacks the foliage and tubers of the potato plant and causes rotting. Says Brock: “It’s a fungal disease, which likes warm, damp conditions and is particularly prevalent during wet summers.” 

The RHS says on its website: “Earthing up potatoes will help to protect the tubers from blight spores washed down into the soil from lesions on the leaves or stems.” 

The RHS also adds that first early cultivars are more likely to escape infection, as levels of the disease tend to increase as summer progresses.