What is a seed potato?
A seed potato is not a botanical seed but a small, whole potato tuber or a piece of a larger tuber used for asexual reproduction. This means that a new potato plant is grown as a clone of its parent, ensuring it retains the same genetic characteristics. Certified seed potatoes undergo a rigorous process to meet high-quality standards set by certifying agencies, like the United Nations Economic Commission for Europe (UNECE). These standards ensure the tubers are true-to-type for the variety and free from diseases and pests.
To become certified, seed potatoes are typically grown from pathogen-tested plant tissue cultures and multiplied in controlled environments, such as screen houses, before being planted in the field. Field inspections are conducted throughout the growing season to check for diseases, pests, and varietal purity. This meticulous process helps guarantee gardeners a robust, healthy, and high-yielding starting material.
The case against planting eating potatoes
While a store-bought eating potato might sprout if left in a warm, light place, planting it is a risky endeavor for several significant reasons. Most commercial potatoes are not grown under the strict regulations of a seed certification program. This means they can harbor viruses, fungi, or bacteria that won't harm humans but can devastate a garden or entire field.
Common risks associated with planting eating potatoes:
- Sprout inhibitors: The majority of non-organic potatoes in grocery stores are treated with chemical sprout inhibitors, like chlorpropham (CIPC), to prevent them from sprouting on the shelf. These inhibitors can make the potatoes nonviable or result in a weak, low-yielding plant. Organic potatoes are not treated with these chemicals, making them a slightly less risky, but still unadvised, option.
- Disease transmission: The greatest risk is introducing persistent diseases into your soil. Pathogens like late blight can linger in the soil for years, infecting future crops and creating a long-term problem for your garden.
- Unknown lineage: With an eating potato, you have no guarantee of its genetic purity or vigor. This means you might get a disappointing crop with a poor yield or inferior potato quality.
Key differences between seed potatoes and eating potatoes
Certification and Disease Control
The most significant difference is the certification process. Seed potatoes are grown in a highly controlled environment and inspected to meet stringent health standards. They are certified to be free of common potato diseases and pests, ensuring that you start with a clean slate. Conversely, eating potatoes lack this guarantee and can carry pathogens. For a home gardener, this means the difference between a successful harvest and a crop wiped out by disease.
Chemical Treatment
As mentioned, eating potatoes are routinely treated with sprout inhibitors to extend their shelf life in grocery stores. Seed potatoes are never treated with such chemicals, as their very purpose is to sprout and grow. This chemical treatment makes most grocery store potatoes unsuitable for planting, as it directly hinders the sprouting process necessary for growth.
Purpose and Maturity
Seed potatoes are grown to a specific physiological maturity to ensure strong sprouting vigor and optimal storage. This focused cultivation results in tubers that are ready to produce healthy, vigorous new plants. Eating potatoes, however, are harvested for food, and their maturity and storage conditions are optimized for consumption, not planting.
A comparison: Seed vs. Eating Potatoes
| Feature | Certified Seed Potatoes | Eating (Grocery Store) Potatoes |
|---|---|---|
| Purpose | Grown specifically for planting and propagation. | Cultivated and sold for human consumption. |
| Certification | Monitored and certified disease-free by agencies. | Not certified for planting; health status unknown. |
| Chemicals | Never treated with sprout inhibitors. | Non-organic types often treated with sprout inhibitors. |
| Genetic Purity | True-to-type, ensuring predictable yield and quality. | Genetic lineage not guaranteed for replication. |
| Disease Risk | Low risk of introducing soil-borne pathogens. | High risk of introducing pests and diseases. |
| Performance | Results in a more vigorous, high-yielding crop. | May result in a failed crop or poor yield. |
Can you plant an organic grocery store potato?
Because they are not treated with chemical sprout inhibitors, organic potatoes are sometimes considered a less risky alternative to conventional eating potatoes. However, they still lack the critical certification that guarantees they are disease-free. While you might get a successful crop from an organic spud, you risk introducing latent diseases into your garden. For this reason, most gardening experts still recommend using certified seed potatoes for the best results and soil protection. For home gardeners in Australia, some have reported success planting store-bought varieties, but they also acknowledge the risk of disease.
Home gardening tips for seed potatoes
For a successful potato harvest, start with high-quality certified seed potatoes. Here are some quick tips:
- Chitting: Three to four weeks before planting, place your seed potatoes in a cool, light area (out of direct sunlight) to encourage sprouting, a process called 'chitting'. This gives the plant a head start and can lead to a healthier crop.
- Cutting: Large seed potatoes can be cut into pieces, each containing at least one or two 'eyes'. Let the cut surfaces dry and form a callous for a couple of days before planting to prevent rot.
- Planting: Plant the chitted or cut pieces in well-drained, airy soil, covering them with a few inches of dirt. As the plant grows, add more soil around the stem, a process known as 'hilling,' to encourage more tubers to form.
- Fertilizing: Potatoes benefit from potassium-rich fertilizers, but too much nitrogen can lead to excessive foliage growth at the expense of tuber development.
Conclusion: The importance of certified seed potatoes
While a potato is a potato, the differences between certified seed potatoes and eating potatoes are crucial, particularly for anyone looking to grow their own. The controlled, disease-free environment in which seed potatoes are cultivated ensures a clean and vigorous starting point, mitigating the risks of chemical inhibitors and soil-borne pathogens present in many grocery store varieties. Using certified seed potatoes is a foundational best practice that provides peace of mind and significantly increases the chances of a healthy, bountiful harvest for years to come. For home gardeners, this investment in quality pays off in healthier plants, higher yields, and superior flavor. Reference: UNECE Seed Potatoes Standard
