Harvesting your own potatoes is one of the most rewarding experiences for any gardener. But knowing exactly when to dig up those buried treasures can be tricky. This comprehensive guide will help you understand the telltale signs that your potato plants are ready to be harvested, ensuring a bountiful and delicious yield.
Understanding Potato Plant Growth
Before we dive into the harvesting signals, let’s quickly review the potato plant’s life cycle. Potato plants, members of the nightshade family, grow from seed potatoes, which are essentially potato tubers with eyes (buds) from which new shoots emerge.
Once planted, the seed potato sprouts and sends up green foliage above ground. This is the vegetative growth phase. Underground, roots and stolons (underground stems) develop, and the potatoes themselves begin to form on the ends of these stolons.
Flowering may or may not occur, depending on the potato variety. After flowering, the plant focuses on bulking up the potatoes underground, storing energy in the tubers.
The Most Obvious Sign: Yellowing and Dying Foliage
The most reliable indicator that your potatoes are nearing maturity is the state of the foliage. As the potatoes mature, the plant begins to divert its energy away from the above-ground growth and towards the tubers. This causes the leaves and stems to turn yellow, then brown, and eventually die back.
This process is often referred to as senescence. When approximately 70-80% of the foliage has died back, it’s a strong indication that your potatoes are ready for harvest. This signals that the tubers have reached their mature size and the skins have thickened.
Think of it like this: the plant is telling you it has done its job. The potatoes have grown, and the plant is now naturally winding down.
Why is Foliage Dieback Important?
Foliage dieback is crucial because it signifies that the potato skins have begun to harden. Thickened skins are essential for protecting the potatoes during storage and preventing them from bruising or rotting. Potatoes harvested before the foliage dies back tend to have thin, easily damaged skins.
Timing is Everything: Considering the Variety and Planting Date
The time it takes for potatoes to mature varies depending on the variety and the planting date. Early-season varieties, like ‘Irish Cobbler’ or ‘Yukon Gold’, typically mature in 70-80 days. Mid-season varieties, such as ‘Kennebec’, take around 90-100 days. Late-season varieties, like ‘Russet Burbank’, can take 120 days or more.
Keep track of the planting date and the expected maturity date for your specific potato variety. This information can be found on the seed potato package or from your local garden center. This will provide a general timeline for when to start looking for signs of maturity.
However, relying solely on the days to maturity is not ideal. Environmental factors, such as temperature and rainfall, can influence the growth rate. It’s always best to combine the expected maturity date with the visual cues from the plant.
The “Test Dig”: Unearthing a Few Potatoes
If you’re unsure whether your potatoes are ready, perform a “test dig.” This involves carefully digging up a few plants to check the size and skin quality of the potatoes.
Choose a plant that shows significant foliage dieback. Gently loosen the soil around the base of the plant with a garden fork or shovel, being careful not to damage the potatoes. Lift the plant and examine the tubers.
What to Look for During the Test Dig
- Size: Are the potatoes the size you expect for the variety you are growing? Consider the intended use. If you want small “new potatoes”, harvest earlier.
- Skin Thickness: Rub the skin of a potato with your thumb. If the skin rubs off easily, the potatoes are not yet mature and should be left in the ground for longer. If the skin is firmly attached and doesn’t rub off easily, the potatoes are ready to harvest.
- Overall Appearance: Are the potatoes firm and free from blemishes or diseases?
If the test dig reveals that the potatoes are still small or the skins are too thin, wait a week or two and perform another test dig.
Specific Stages: New Potatoes vs. Mature Potatoes
It’s important to distinguish between harvesting “new potatoes” and harvesting mature potatoes for storage.
- New Potatoes: These are small, immature potatoes harvested before the foliage has completely died back. They have thin, delicate skins and a creamy texture. New potatoes are best eaten soon after harvesting and do not store well. Harvest them about 2-3 weeks after flowering, or when the potatoes are roughly the size of golf balls or small eggs.
- Mature Potatoes: These are fully grown potatoes with thick, hardened skins. They are ideal for long-term storage. Allow the foliage to die back completely before harvesting mature potatoes.
Ideal Weather Conditions for Harvesting
Whenever possible, choose a dry, sunny day for harvesting potatoes. Avoid harvesting after heavy rain, as the soil will be wet and the potatoes will be more susceptible to rot. Dry soil makes the digging process easier and helps to prevent the potatoes from getting bruised or damaged.
How to Harvest Potatoes Properly
Now that you know how to tell when your potatoes are ready, let’s discuss the best way to harvest them.
- Loosen the Soil: Using a garden fork or shovel, carefully loosen the soil around the potato plants. Work from the outside of the plant inwards to avoid spearing the potatoes.
- Gently Lift: Gently lift the plant and surrounding soil. Use your hands to carefully remove the potatoes from the soil.
- Inspect and Sort: Inspect each potato for damage, disease, or pests. Discard any potatoes that are rotten or severely damaged.
- Cure (for Storage Potatoes): Allow the potatoes to cure in a cool, dry, and dark place for about 1-2 weeks. This process helps to harden the skins and heal any minor wounds, improving their storage life.
Potato Plant Problems That Can Impact Harvest Timing
Several issues can affect when your potato plants appear ready to harvest. Understanding these problems and how to address them is critical.
Late Blight
Late blight, a fungal disease, can cause rapid foliage dieback. Unlike the natural senescence process, late blight causes dark, water-soaked lesions on the leaves and stems. The foliage will collapse quickly, and the tubers may develop a reddish-brown rot. If late blight strikes, it’s best to harvest the potatoes as soon as possible, even if they are not fully mature, to prevent further rot. Remove and destroy all infected foliage and tubers.
Early Blight
Early blight, another fungal disease, causes brown, circular spots on the leaves. While not as devastating as late blight, early blight can weaken the plants and reduce yields. If your plants are affected by early blight, harvest the potatoes when they reach a reasonable size, even if the foliage hasn’t completely died back.
Pests
Potato beetles and other pests can defoliate potato plants, mimicking the appearance of natural dieback. Inspect your plants regularly for pests and take appropriate measures to control them. If pests are causing premature defoliation, you may need to harvest the potatoes earlier than expected.
Nutrient Deficiencies
Lack of essential nutrients, such as nitrogen, phosphorus, or potassium, can also cause foliage problems and affect maturity. Ensure your potato plants receive adequate nutrition throughout the growing season.
Storing Your Harvested Potatoes
Proper storage is essential for preserving your potato harvest.
- Curing: As mentioned earlier, curing potatoes is crucial for long-term storage.
- Storage Conditions: Store cured potatoes in a cool, dark, and well-ventilated place. The ideal storage temperature is between 40-50°F (4-10°C). A root cellar or unheated garage is often a good option.
- Avoid Light: Exposure to light can cause potatoes to turn green and produce solanine, a toxic alkaloid. Store potatoes in opaque containers or cover them with burlap sacks.
- Regular Inspection: Check your stored potatoes regularly for signs of rot or sprouting. Remove any damaged potatoes immediately to prevent the spread of rot.
Final Thoughts: Harvesting with Confidence
Knowing what to look for in potato plants allows you to get the biggest and best harvest. By understanding the stages of growth, the signs of maturity, and potential problems, you can confidently harvest your potatoes at the optimal time, enjoying the fruits (or rather, tubers) of your labor. Happy harvesting!
How can I tell if my potato plants are ready to harvest based on the foliage?
As potato plants mature and their tubers are ready for harvest, the foliage will begin to yellow and die back. This is a natural part of the plant’s life cycle and a key indicator that the potatoes beneath the soil are nearing maturity. The leaves may turn brown, become brittle, and eventually wither away entirely. This die-back signals the plant is diverting its energy from foliage growth to tuber development, thickening the skins and increasing the potato’s size.
However, foliage die-back can also be caused by disease or pests. It’s important to carefully inspect the plants for other symptoms such as lesions, unusual spots, or signs of infestation before assuming the potatoes are ready. If the die-back is premature and accompanied by other concerning signs, it’s best to investigate further to rule out other potential issues before harvesting.
What is “stopping” and how does it affect potato harvest readiness?
“Stopping,” also known as “killing” or “desiccating,” refers to the intentional removal or killing of potato plant foliage several weeks before harvesting. This practice encourages the potato skins to thicken, making them less susceptible to damage during harvest and storage. Stopping also halts further tuber growth, allowing for a more uniform potato size.
By stopping the foliage, you’re essentially signaling to the plant that it’s time to focus on curing and strengthening the potatoes. Different methods can be used, including cutting the stems, applying herbicides (if appropriate and allowed), or even physically pulling the plants. Knowing when to stop depends on the potato variety and your desired potato size, generally around two to three weeks before your planned harvest.
Are there different harvest stages for potatoes, and how do they look different?
Yes, potatoes can be harvested at different stages, often referred to as “new potatoes” and “mature potatoes.” New potatoes are harvested early, typically when the plants are still flowering and the tubers are small. They have thin, easily rubbed-off skins and a delicate, waxy texture. The foliage may still be green, although you can dig around the plant to check the potato size.
Mature potatoes are harvested later, after the foliage has died back. These potatoes have thicker skins, a higher starch content, and are better suited for long-term storage. The skins should be firm and set, not easily damaged by handling. Waiting for complete foliage die-back is generally recommended for mature potato harvests.
How do I check potato size and readiness without harvesting the entire plant?
To assess potato readiness without uprooting the entire plant, carefully dig around the base of one or two plants. Gently loosen the soil and feel for the tubers. You can carefully excavate a few potatoes to check their size, skin thickness, and overall appearance.
After inspecting the sample potatoes, carefully recover the roots of the plant you disturbed with soil. This allows the plant to continue producing if the potatoes aren’t quite ready. If the sample potatoes are the desired size and the skins seem firm, you can proceed with harvesting the remaining plants.
Does potato variety affect when I should harvest?
Yes, the variety of potato significantly impacts the harvest time. Early-season varieties mature faster, typically within 70-90 days, while mid-season varieties take 90-120 days, and late-season varieties can take over 120 days or more to reach maturity. Different varieties also develop at different rates, with some developing thick skins more quickly than others.
It’s important to know the specific variety of potato you are growing and consult the seed packet or supplier information for recommended harvest times. This information will provide a general timeframe, but remember to also observe the plant’s foliage and perform test digs to determine the optimal harvest time for your specific growing conditions.
What soil conditions indicate potato harvest readiness?
While not a direct indicator, the soil surrounding your potato plants can provide some clues about harvest readiness. If the soil has been consistently moist but not waterlogged throughout the growing season, this is generally ideal for potato development. Dry soil can stress the plants and lead to smaller, less flavorful potatoes.
Well-drained soil is also crucial. Excessively wet or compacted soil can lead to rot and disease, which can affect the quality of the potatoes and potentially require an earlier harvest. While healthy soil doesn’t directly indicate readiness, problematic soil conditions might accelerate the harvest to salvage the crop before further damage occurs. Observe the soil moisture and drainage throughout the growing season.
What should I do with the potato plants after harvesting the potatoes?
After harvesting your potatoes, remove the remaining plant debris, including the stems and any remaining leaves. Dispose of this material properly, especially if you suspect any disease or pest infestations. Do not compost diseased foliage, as it can spread pathogens in your garden. Burning (if permitted) or discarding the foliage in the trash are safer options.
Consider planting a cover crop on the harvested potato bed. This can help improve soil health, prevent erosion, and suppress weeds. Cover crops like buckwheat, oats, or rye are excellent choices for enriching the soil after harvesting potatoes, preparing the bed for future plantings.