Signs Your Maincrop Potatoes Are Ready
Deciding precisely when to harvest maincrop potatoes requires careful observation of the plants themselves. Unlike early or second early varieties, maincrops are bred for maturity later in the season, typically from late summer through to autumn. The most telling sign that your maincrop potatoes are approaching maturity is the dieback of their foliage.
When the leaves and stems of your potato plants begin to turn yellow, wither, and eventually collapse, it signals that the plant has finished its growing cycle. This natural senescence means the energy it once directed into foliage growth is now primarily stored in the tubers beneath the soil. However, simply waiting for complete dieback isn't always the optimal strategy, especially if you wish to store your harvest. For best results and easier lifting, it's advisable to stop watering the plants once the foliage shows significant yellowing. This helps the potato skins to harden off, reducing the risk of damage during harvesting and improving their storage potential. A period of dry weather following foliage dieback is ideal for hardening the skins.
Another indicator, though less precise, is the flowering stage. For many potato varieties, flowering occurs well before the tubers are fully mature. While abundant flowering might suggest growth, the subsequent yellowing and dying back of the leaves is the definitive signal for harvest readiness, particularly for maincrops. You can also gently probe the soil around the base of a plant with your fingers or a small fork to check the size of the developing tubers. If they have reached a desirable size and their skins are starting to feel firm rather than easily rubbing off, they are likely ready.
- Wait for foliage to yellow and die back.
- Harden skins by stopping watering before harvest.
- Check tuber size and skin firmness.
- Typical harvest is late summer to autumn.
Determining the Ideal Harvest Window
When can you typically expect to harvest maincrop potatoes? These varieties are planted with the intention of yielding a substantial crop that will last through the colder months. Consequently, their maturity period is naturally longer. While early potatoes might be ready for lifting just 10-12 weeks after planting, maincrops often require 18-25 weeks, or even longer, depending on the specific cultivar and your local climate conditions.
This extended growing period means that planting times are critical. If you planted your seed potatoes in early spring, as is common, you're looking at a harvest window that usually begins in late August and can extend through September and into October. It is crucial to avoid harvesting maincrop potatoes while the foliage is still lush and green. Doing so means you are likely to yield smaller tubers and compromise their storage capability. The plant needs its full growing season to develop its full potential, both in terms of tuber size and skin thickness for preservation.
If you're unsure about the specific maturity period for your variety, consult the packaging the seed potatoes came in; reputable suppliers will list the approximate days to maturity.
Consider your local weather patterns. If you live in an area prone to early autumn frosts, it's generally advisable to lift your maincrop potatoes before the first hard frost is expected. Frost can damage the tubers, making them susceptible to rot during storage. A week or two before you plan to lift, you can snip off the remaining dead or dying foliage to further encourage skin hardening and make locating the rows easier. This also helps to reduce the risk of blight infecting the tubers through the dying stems.
Alternative Indicators for Maturity
While foliage dieback is the primary cue, there are other factors to consider. The weight of the haulms (the leafy tops) can be an indicator; when they lie flat on the ground, it suggests the plant has completed its primary growth. For gardeners growing potatoes in bags or containers, the visible drying out of the top layer of compost, coupled with the plant's general decline, is a strong signal. The aim is to achieve tubers with well-developed skins, which are dry and firm to the touch, not easily scraped off with a thumbnail.
How to Harvest Maincrop Potatoes Correctly
Once you've determined that your maincrop potatoes are ready, the method of harvesting is key to a successful yield and good storage. Begin by carefully removing any remaining dead foliage from the soil surface. This clears the ground, making it easier to locate the tubers and reducing the chance of accidental damage to the crop.
The most common method involves using a garden fork or a spade. Start digging a good distance away from the main stem of the plant, typically about 20-30 cm out. This is to avoid piercing the tubers with the tines of the fork or the edge of the spade. Gently push the fork into the soil and lever upwards, loosening the soil around the plant. You can then carefully reach into the loosened soil and begin to unearth the potatoes. It’s often best to work from the outside of the plant inwards, as the largest tubers tend to be found furthest from the stem.
For those growing potatoes in pots or growing bags for potatoes, the process is simpler. You can often empty the entire contents of the bag or pot onto a clean sheet or tarpaulin. Then, carefully sift through the compost and soil to collect all the potatoes. This method minimises the risk of damaging individual tubers, as you have more control over the separation process.
Post-Harvest Care for Storage
After lifting your maincrop potatoes, it's vital to handle them with care. Avoid bruising or damaging them, as any injury can lead to rot during storage. Lay the harvested potatoes out on the soil surface (if dry and not too sunny), or on clean trays or newspaper in a cool, dry, well-ventilated shed or garage for a few hours to a couple of days. This allows any remaining soil to dry and flake off, and further hardens the skins. Sunlight can cause potatoes to turn green and develop solanine, which is toxic, so avoid direct sun exposure during this curing period. Once they are dry and the skins are firm, they are ready for storage.
The success of storing maincrop potatoes hinges on harvesting them at the right time and ensuring their skins are mature and dry.
Troubleshooting and Storage Tips
What happens if you miss the ideal harvest window for your maincrop potatoes? Harvesting too early means you will have smaller, immature tubers with thin skins that are prone to damage and won't store well. Conversely, leaving them in the ground too long, especially in wet conditions, significantly increases the risk of rot, blight, and pest damage. Potatoes left in waterlogged soil are almost certain to spoil. If heavy rain is forecast for an extended period after the foliage has died back, it's better to lift them, even if the skins aren't perfectly hardened, than to risk losing the entire crop to rot. The key is to balance the need for mature skins with the risks posed by adverse weather.
For optimal storage, maincrop potatoes should be kept in a cool, dark, and frost-free location. A temperature of around 7-10°C is ideal. Avoid storing them in plastic bags, as this traps moisture. Burlap sacks, paper bags, or shallow wooden crates are much better choices. Ensure good air circulation around the potatoes. Regularly check your stored crop for any signs of rot or sprouting, removing any affected potatoes immediately to prevent them from spoiling the rest of the batch. Do not store potatoes with apples, as the ethylene gas released by apples can encourage potatoes to sprout prematurely.
Inspect your stored potatoes periodically throughout the winter and remove any that show signs of sprouting or softening, as these will not be suitable for consumption and can affect others.
Considerations for Different Growing Methods
Whether you're growing potatoes in open ground, raised beds, or growing bags for potatoes, the fundamental signs for harvesting remain the same: foliage dieback and skin maturity. However, the practicalities differ. For plants in containers, you have more control over watering and can more easily stop it to harden skins. Harvesting from open ground requires more care to avoid damaging tubers with tools. Understanding how to plant potatoes and the specific needs of seed potatoes you use will inform the entire growing and harvesting process. Aim to harvest when the conditions are dry to make the job easier and improve the storage quality of your crop.