Potatoes are one of the most rewarding crops to grow in the garden, allotment or even in containers. They are relatively easy to cultivate and provide generous yields that can keep a household supplied for weeks or even months. However, while planting potatoes may be straightforward, knowing when to harvest them requires more understanding. Timing is crucial, as harvesting too early can mean small, underdeveloped tubers, while waiting too long can cause them to become diseased or sprout in the ground. By learning the signs that indicate potatoes are ready and by appreciating the differences between early, maincrop and late varieties, gardeners can make the most of this staple vegetable.
The life cycle of a potato plant
To understand when to harvest, it helps to look at how potato plants grow. Potatoes are tubers that develop underground on stolons, which are side shoots of the plant. After planting, the seed potato sends up green shoots above the soil and roots beneath. As the plant matures, it produces flowers, and beneath the soil, the tubers begin to swell. The timing of harvesting depends on how far along the plant is in this life cycle and the type of potato grown. Early potatoes mature more quickly, while maincrop varieties take longer but yield larger tubers.
Harvesting early potatoes
Early potatoes, sometimes called new potatoes, are generally harvested in late spring or early summer. These varieties are ready around 10 to 12 weeks after planting. A key sign is when the plants begin to flower, which indicates that small tubers have formed underground. At this stage, you can gently dig around the base of the plant to check the size of the potatoes. Early potatoes are best enjoyed fresh, as they have a tender skin and a sweet flavour. Because their skins are thin, they do not store well, so harvesting should be timed to coincide with when you want to eat them.
Harvesting maincrop potatoes
Maincrop potatoes are usually ready from late summer through autumn, around 18 to 20 weeks after planting. These varieties need more time to develop but produce larger tubers and higher yields. The traditional sign that maincrop potatoes are ready is when the foliage begins to yellow and die back. Once the leaves and stems have withered, the energy has moved into the tubers, and they are at their peak size. Cutting back the dead foliage about two weeks before harvesting allows the skins to firm up, which improves storage quality. Maincrop potatoes can be stored for several months if harvested and cured correctly.
The role of weather in harvest timing
Weather plays a significant part in determining the right moment to harvest potatoes. Warm, sunny conditions encourage rapid growth, while cool, wet weather can slow development. Heavy rain close to harvest can make the soil waterlogged, increasing the risk of rot. Ideally, potatoes should be harvested when the soil is dry, as this makes lifting them easier and reduces the chances of damaging the tubers. Storing potatoes with damp soil still clinging to them can also shorten their shelf life, so dry conditions are best.
Checking potatoes before full harvest
Gardeners often do a test dig before committing to a full harvest. By gently lifting one plant and examining the tubers, you can assess whether they are the right size and whether the skins have set. If the potatoes are still small or the skins rub off easily, it is worth waiting another week or two. This trial and error approach ensures that you harvest at the perfect time rather than relying solely on dates or general guidelines.
Harvesting techniques
Harvesting potatoes requires care to avoid damaging the tubers. A garden fork is often used, inserted at a distance from the plant to avoid spearing the potatoes. The soil is then gently lifted and the potatoes collected by hand. For those growing in containers, harvesting is simpler, as the soil can be tipped out and the tubers collected easily. Regardless of method, care should be taken to remove all potatoes from the soil, even small ones, as leftovers can sprout the following year and interfere with crop rotation.
Curing and storing potatoes
Once harvested, potatoes intended for storage should be cured. This involves leaving them in a cool, dry, dark and well ventilated space for around two weeks. Curing allows the skins to toughen, which helps protect the tubers from disease and prolongs storage life. After curing, potatoes should be stored in paper or hessian sacks in a dark place with a temperature of around 4 to 10 degrees Celsius. They should not be kept in plastic bags, as this traps moisture and encourages rot. Properly stored maincrop potatoes can last for several months, providing food well into winter.
Signs of overripe potatoes
If potatoes are left in the ground too long after the foliage has died back, they may begin to sprout or be attacked by slugs and diseases such as blight. Overripe potatoes may also develop thick, coarse skins, making them less desirable for eating. Harvesting in good time avoids these problems and ensures that the tubers are at their best for both taste and storage. Keeping an eye on the condition of the foliage and soil will help you avoid leaving potatoes in the ground for too long.
Regional and variety differences
The timing of potato harvests can vary across the UK depending on climate and variety. In southern regions with warmer weather, potatoes may be ready earlier in the season. In northern or cooler areas, harvests are often later. Varieties also differ, with some maturing in as little as 10 weeks and others taking up to 22 weeks. Reading the seed packet or supplier’s guidance helps you estimate when your chosen variety will be ready, but visual signs such as flowering and foliage dieback remain the most reliable indicators.
Why harvesting time matters
Harvesting potatoes at the right time maximises yield, flavour and storage potential. Early potatoes harvested too late can lose their tender texture, while maincrop potatoes harvested too soon may be small and unsuitable for storage. Harvesting at the correct stage ensures that you enjoy the best qualities of each variety, whether that is the delicate sweetness of new potatoes or the robust storage qualities of maincrops. Timing also helps protect plants from disease and pests that can quickly ruin a crop if left too long in the soil.
Conclusion
So, when should you harvest potato plants? The answer depends on the type of potato and the conditions in which it is grown. Early potatoes are ready around 10 to 12 weeks after planting, often when the plants begin to flower, while maincrop varieties are best harvested 18 to 20 weeks after planting once the foliage has died back. Weather, soil conditions and variety all play a role, but the key is to observe the plants and check the tubers before committing to a full harvest. By harvesting at the right time and curing and storing potatoes correctly, you can enjoy a plentiful supply of this staple crop throughout the year.
