Understanding Potato Harvest Indicators
Knowing precisely how do you know when potatoes are ready to harvest involves observing multiple signs, rather than relying on a single indicator. The timing itself is influenced by the potato variety you are growing; early, mid, and late season types all have different maturity periods. Generally, most potatoes are ready to dig between 70 and 120 days after planting, but this is just a guideline.
The most significant visual cue that your potato plants are nearing readiness is the state of their foliage. When the green leaves and stems start to yellow, wither, and eventually die back, it signals that the plant has finished its growth cycle and the energy is now concentrated in the tubers. For early or 'new' potatoes, you can often harvest them while the foliage is still green, but for mature, maincrop varieties intended for storage, waiting for the haulms (the above-ground stems and leaves) to die back is essential. This process allows the skins of the potatoes to toughen up, which is vital for preventing damage during harvesting and for ensuring a longer storage life.
When to Dig Early Potatoes
If you're eager for a taste of your own homegrown new potatoes, you don't have to wait for the plant to completely finish. About two to three weeks after the plants have flowered, you can begin to carefully investigate. Gently scrape away some soil around the base of the plant with your fingers or a small hand trowel to check the size of the developing tubers. If they are of a pleasing size for eating – typically golf ball to tennis ball size – you can harvest some. Remember to only take what you need, leaving the rest to grow larger, and avoid disturbing the main root system too much. Harvesting new potatoes this way while the plant is still relatively healthy is perfectly fine and will not harm the plant's overall production for the season.
Patience for Maincrop Varieties
For maincrop potatoes, which are grown for their larger size and storage potential, patience is key. You must wait until the haulms have completely died back. This usually occurs naturally later in the season, often by late summer or early autumn, depending on your climate and when you planted your seed potatoes. If you harvest too early, the skins will be thin and easily damaged, leading to bruising and rapid spoilage during storage. Allowing the skins to mature and harden is a critical step for successful long-term storage.
Protect your crop from frost. As autumn approaches, keep an eye on weather forecasts. A light frost might not kill the plant immediately, but a hard frost can damage the tubers, making them unsuitable for storage.
The appearance of the tubers themselves also provides clues. When the plants have died back and you begin to dig, the potatoes should feel firm and have skins that are relatively difficult to rub off with your thumb. If the skins slip off easily, the tubers are likely immature and will not store well. This skin toughness is a definitive sign that the potatoes have reached their maturity.
The skin texture is a key indicator of maturity.
If you're growing potatoes in containers or growing bags for potatoes, the signs are similar, though the harvest might be slightly earlier due to more controlled conditions and potentially less root development compared to in-ground planting. Always check the specific variety's expected maturity date and observe the plant's foliage and tuber skins.
The Harvesting Process: Digging Your Spuds
Once you've confirmed that your potato plants are ready for harvest, the actual digging needs to be done with care. The primary goal is to extract the tubers without damaging them, especially if you plan to store them. This is where the 'alternatives' in harvesting come into play – you can choose to dig them all at once or gradually, depending on your needs and the variety.
Preparation and Tools
Before you begin digging, it's advisable to stop watering your potato plants a week or two before the intended harvest date. This helps the skins to dry and harden, making them more robust. On the day of harvesting, choose a dry day. If the soil is wet and heavy, it makes digging much harder and increases the risk of bruising the potatoes.
You'll need a sturdy digging fork or a spade. Avoid using tools with sharp edges if possible, as these are more likely to cut into the tubers. The general method is to start digging a good distance away from the main stem – at least six inches to a foot – to avoid spearing the potatoes. Work your way around the plant, loosening the soil and carefully lifting the entire clump of soil and potatoes out of the ground.
Handle dug potatoes gently to prevent bruising.
Extraction and Initial Curing
Once the soil is loosened, carefully pick through it to find all the potatoes. It's common to miss a few, which can then volunteer and grow the following year, hence the saying 'a potato in the ground is worth two in the pot'. After you've gathered the harvest, spread the potatoes out on the soil surface (if dry and sunny) or on newspaper or trays in a sheltered, well-ventilated spot for a few hours. This allows any remaining soil to dry and facilitates the 'curing' process. Curing allows any minor nicks or scratches on the skins to heal over, further improving storage potential.
For new potatoes, this curing step is less critical as they are typically eaten fresh and don't require long-term storage. However, for maincrop varieties destined for the pantry, curing is a vital step. You can also brush off any dry soil gently; avoid washing them unless absolutely necessary, as moisture can encourage rot.
The decision to harvest all at once or in stages depends on your available storage space and how much you plan to use immediately. If you have ample, cool, dark storage, you might wait for the majority of your maincrop to mature fully. If space is limited, or you wish to enjoy a steady supply, you might opt for a staggered harvest as the plants die back.
The best alternative is to harvest on a dry day.
Potato Varieties and Their Maturity
When you ask how do you know when potatoes are ready to harvest, it's crucial to remember that different types mature at different rates. Understanding the category of potato you've planted is as important as observing the plant itself. This knowledge helps manage expectations and plan your harvest schedule effectively, especially when growing potatoes in pots or directly in the soil.
Classifying Potato Maturity
Potato varieties are broadly classified into three main groups based on their maturity period:
- First Early (or 'New') Potatoes: These are the quickest to mature, typically ready to harvest around 70-90 days after planting. They are often harvested when small, with delicate skins, and are best eaten fresh. Their foliage may still be green when you dig for them.
- Second Early Potatoes: These fall between the first earlies and maincrops, usually ready in about 90-110 days. They offer a good balance, producing decent-sized tubers that can be eaten fresh or stored for a moderate period.
- Maincrop Potatoes: These take the longest to mature, requiring 110-120 days or more. They produce large, floury tubers well-suited for baking, mashing, and long-term storage. It is imperative to wait for the haulms to die back completely before harvesting these varieties to ensure their skins are tough enough for storage.
When planting seed potatoes, always check the variety's specific maturity description. This information is usually provided by the supplier and is a reliable indicator of when to expect your crop.
Factors Influencing Maturity
Beyond variety, several environmental factors can influence when your potatoes are ready. Soil temperature, moisture levels, and sunlight exposure all play a role. For instance, if you planted seed potatoes in cold, damp soil, they may take longer to establish and mature than those planted in warm, well-drained conditions. Similarly, a particularly sunny and warm growing season can accelerate maturity, while a cool, wet summer might delay it.
Consider the growing conditions you provided. Potatoes grown in growing bags for potatoes or containers might mature slightly faster than those in open ground, especially if they are placed in a sunny spot. Conversely, if the containers dry out too quickly or become waterlogged, it can stress the plants and affect tuber development.
The variety's classification is your primary guide for harvest timing.
It's also worth noting that if you intend to store your potatoes over winter, maincrop varieties are the best choice. Harvesting them at the correct stage, after the haulms have died back and after a curing period, is paramount for achieving good storage results. Early varieties are generally not suited for long-term storage due to their thin, tender skins.
If you're unsure about a specific variety, observing the plant's behaviour – flowering, dying back – combined with the general maturity window for its type, will give you the best indication of readiness.
Troubleshooting and Storage
Even with careful observation, harvesting can sometimes present challenges, and knowing how to store your potatoes correctly is the final step in a successful crop. If you've followed the advice on when to harvest, you're already halfway there.
Common Harvest Issues
One common issue is premature yellowing or wilting of the haulms, which can be caused by disease, pests, or water stress. If this happens before the typical maturity period for your variety, it's a difficult situation. For early varieties, you might still be able to salvage some usable tubers, though they may be smaller than expected. For maincrops, early wilting might mean the skins haven't fully hardened, making them unsuitable for long-term storage. In such cases, it's best to use them as soon as possible.
Another problem can be over-harvesting or damaging tubers during digging. Using a fork instead of a spade, digging a good distance from the plant, and carefully sifting through the soil can minimise this. If you do nick a potato, it should ideally be used first, or the damaged skin can be trimmed off if it's minor.
Inspect every potato for damage before storing.
Best Practices for Storing Potatoes
Once harvested and cured (for maincrops), potatoes need specific conditions to store well:
- Cool: Ideal temperatures are between 7°C and 10°C (45°F and 50°F). Too warm, and they'll sprout; too cold, and they can turn sweet and develop a poor flavour when cooked.
- Dark: Light encourages potatoes to produce solanine, a toxic green pigment, and makes them sprout. Store them in a dark place like a cellar, shed, or a cupboard away from direct light.
- Ventilated: Good air circulation is essential to prevent moisture buildup, which can lead to rot. Store them in hessian sacks, wooden crates, or shallow boxes, rather than sealed plastic bags.
- Dry: Ensure potatoes are dry before storing. If you've had to wash them due to heavy soil, dry them thoroughly.
Check your stored potatoes periodically for any signs of spoilage. Remove any that are soft, mouldy, or showing signs of rot to prevent it from spreading to the rest of the crop. For new potatoes, which don't store well, keeping them in a cool, dark place for a few days is usually sufficient if you can't eat them immediately.
Avoid storing potatoes with apples. Apples release ethylene gas, which can cause potatoes to sprout prematurely.
By understanding the signs of maturity and following these harvesting and storage tips, you can ensure a successful potato harvest that lasts.