Although called seed potatoes, you dont sow potato seeds. Seed potatoes are small root tubers with numerous buds called eyes. When the ground in your garden gets to about 10 degrees Celsius in the spring, plant seed potatoes in long rows or shallow furrow basins called hills. Numerous fungal diseases potentially destroy seed potatoes, especially once planted in the cool, dark, moist conditions underground. Discard mouldy seed potatoes; do not plant them as they already contain at least one pathogen.
It is possible to use potatoes from last fall’s harvest as seed potatoes in the spring, but it’s not a good idea. Many pathogens, like mold and fungal spores, can’t be seen by the naked eye and can be found on or in potatoes. Garden centres typically sell certified seed potatoes. This label guarantees that the potato variety is real and pure, and that the seed potatoes have been treated to get rid of pathogens or greatly reduce their numbers before they are planted. Always inspect the certified product, as rot and mould may still arise during storage.
As a potato gardener, you’ve likely encountered moldy potato tubers when sorting through your harvest. A fuzzy white or gray mold is common on potatoes in storage. But is it safe to plant those moldy potatoes in the garden? In this article, we’ll explore the risks, look at different potato molds, and discuss when it is and isn’t safe to plant moldy seed potatoes.
Why Potatoes Get Moldy
Potatoes, like other root crops, are prone to mold growth during storage. The main causes include:
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Excess moisture – Wet tubers allow mold spores to thrive. Ensure potatoes are cured and stored in a dark cool dry area.
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Bruising/wounding – Cuts and cracks give mold an entry point Handle potatoes gently to prevent this
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Long storage – Over time, natural anti-fungal compounds decline. Eat or plant stored potatoes within 5-6 months.
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Poor ventilation – Still, stagnant air encourages mold. Ensure good air flow in storage.
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High temperatures – Ideal potato storage temps are 38-40°F. Warmer conditions promote mold.
Common Potato Molds
There are several types of mold that can grow on stored potatoes. Some of the most common include:
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Grey mold – Also called botrytis mold, grey mold forms fuzzy grey or brown spots on tubers. It spreads rapidly in warm, humid conditions.
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Black mold – Appears as black velvety dots on potato skin. This mold produces toxins and makes potatoes unsafe to eat.
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Blue mold – Causes light blue fuzz on tubers. While unsightly, blue mold generally only impacts surface.
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White mold – Grows as thick white fuzz on tubers. Spreads quickly in storage. Less dangerous than black mold.
Is it Safe to Plant Moldy Potatoes?
Whether moldy seed potatoes can be safely planted depends on the specific mold type and extent of mold.
Potatoes with surface mold only – like some blue mold, white mold, or minor grey mold – are generally fine to plant. The mold is unlikely to impact the potato’s growth. Simply brush off any mold before planting. Avoid tubers with deep mold penetration.
However, potatoes showing any signs of black mold should absolutely not be planted. The black mold produces harmful toxins that can spread disease in your garden. It’s better to be safe than risk infecting your soil.
Here are some other tips on planting moldy potatoes:
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Inspect each potato tuber individually and discard any with concerning mold.
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Cut out minor moldy spots rather than discarding the whole potato.
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Plant in a different area than your moldy potatoes were grown previously.
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Clean tools thoroughly after handling to avoid spreading mold spores.
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Consider treating cut seed pieces with a fungicide powder to prevent mold spread.
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Grow mold-resistant potato varieties like Yukon Gold or Red Pontiac if mold has been an issue.
Signs of Healthy Seed Potatoes
When selecting seed potatoes, look for tubers that are:
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Firm, with no soft spots or hollow areas
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Free from dark mold, large blemishes, or extensive rotting
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Intact, without major cracks or wounds that could invite disease
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Reasonably smooth, with few dormant eyes/sprouts
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Not excessively shriveled (some wrinkling is normal)
Healthy seed potatoes will sprout uniformly when planted. If you notice weak sprouts or none at all, disease is likely present.
Storing Potatoes Properly
The best way to avoid moldy potatoes is by providing good storage conditions after harvest:
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Cure fresh dug potatoes 1-2 weeks in warm, humid conditions to thicken skins.
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Store cured potatoes in the dark. Light causes greening and solanine production.
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Choose a location with temperatures around 40°F. Cool but not freezing.
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Ensure potatoes are damp but not wet. Good air circulation prevents condensation.
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Check periodically for mold or rotting tubers. Remove affected potatoes immediately.
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Consume or plant stored potatoes within 5-6 months before quality declines.
Proper harvesting, curing, and storage practices go a long way in preventing mold!
What If My Whole Potato Crop Has Mold?
If all your potato tubers have mold, it’s best to discard the entire harvest. Purchase certified disease-free potatoes from a garden store to use as seed for next year.
Thoroughly clean any containers or areas used to store the moldy potatoes to prevent spreading spores. Sterilize tools with bleach after digging infected potatoes.
To protect future crops:
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Improve crop rotation and avoid planting potatoes in the same soil two years in a row.
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Space and prune plants to encourage good air flow and drainage.
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Treat seed potatoes with antifungal products like neem oil before planting.
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Consider mold resistant potato varieties like Elba, Jacqueline Lee, or Missaukee.
Final Thoughts on Moldy Seed Potatoes
Finding mold on stored potato tubers is fairly common but easily preventable. While potatoes with surface mold can often still be planted, those with dark fuzzy mold should always be discarded. With proper harvesting, storage, and rotation practices, you can avoid disease issues and harness the full potential of your homegrown potato crop.
Save Potatoes, Bulbs, and Rhizomes that Show Signs of Mold & Fungus with a Hydrogen Peroxide Spray
FAQ
Are potatoes still good if they have mold?
Can you plant potatoes that have gone bad?
Do you need to remove mold from potatoes?
No, it’s not necessary to do that. However, you have to throw the moldy potato right away, or it will contaminate the whole bunch of potatoes. You can isolate and discard the potatoes near the moldy potato. How Can I Prevent My Potatoes from Getting Mold? There are many ways you can prevent your potatoes from being attacked by fungus and molds.
Can you eat moldy potatoes?
First of all, you must understand that consuming the moldy part of potatoes is not safe because some molds are poisonous. Eating such contaminated potatoes can result in vomiting, nausea, and even food poisoning. The only way to eat potatoes that have gone a little moldy is to cut out and discard the moldy parts and the places around them.
Can you save a potato if it is moldy?
However, you can still save the potato if the mold growth starts in a small spot. Just slice off or cut off the part where the mold starts to grow to save the rest of the potato. Be sure to cut about an inch around the mold spot to be safe. Do I Need to Throw All the Potatoes If One of Them Is Moldy? No, it’s not necessary to do that.
How do you know if a potato has mold?
Recognizing and Understanding Potato Mold Mold on potatoes usually appears as a fuzzy substance on the skin, especially on bruised or damaged spots. The mold may be brownish, black, white, grey, or even reddish in color. It is a common indicator of spoiled potatoes.