How Do I Know If Seeds Are Bad? A Comprehensive Guide

While the dates on seed packets are more of a 'packed for' guideline than a true expiration date, seeds can and do lose their viability over time due to improper storage, age, and damage. Every gardener eventually faces the challenge of determining if their seed stock is still viable before planting, which can prevent wasted effort and disappointment. The good news is that several straightforward methods exist to test and confirm seed quality.

Quick Summary

This guide outlines how to determine if seeds have gone bad through simple visual checks and practical viability tests, including the float test and the paper towel germination test. It covers the key signs of non-viable seeds, explores why some tests are more reliable than others, and provides proper storage techniques to maximize seed longevity for future seasons.

Key Points

• Visual Signs: Look for discoloration, mold, physical damage, and a soft or shriveled texture, all of which indicate non-viable seeds.

• Paper Towel Test: Use a damp paper towel and a plastic bag to perform a reliable germination test at home, which gives you a clear germination rate percentage.

• Float Test Limitations: The float test is a quick but unreliable indicator of viability, particularly for smaller seeds, and should not be fully trusted.

• Proper Storage is Key: Store seeds in a cool, dark, and dry environment to maximize their longevity and preserve their viability for future planting seasons.

• Bad Seeds = Bad Results: Planting non-viable seeds can lead to poor germination, uneven plant stands, and weak, disease-prone plants.

• Test Before You Plant: Performing a germination test well before your planting season gives you time to purchase new seeds if your old ones have a low germination rate.

Visual Clues: What to Look for in Bad Seeds

Before you even perform a test, a careful visual inspection can often reveal if seeds are non-viable. Look for obvious signs of damage, decay, and discoloration.

• Discoloration: Good seeds typically have a uniform, expected color. Black or speckled seeds can indicate fungal infection or mold, while unusually pale or discolored ones may be heat-damaged.
• Texture and Firmness: A healthy, viable seed should feel plump and firm. Soft, shriveled, or squishy seeds are often empty or damaged internally. This is particularly noticeable in larger seeds like beans and peas.
• Mold or Mildew: Visible mold or mildew is a clear sign that seeds have been exposed to excess moisture, which can cause them to rot. A musty or foul smell also indicates poor storage conditions.
• Physical Damage: Inspect for cracks, holes, or insect bites. Any breach in the seed coat can compromise the embryo's integrity and lead to failed germination.

The Float Test: A Quick, But Flawed, Method

One of the simplest and quickest tests is the float test, which involves placing seeds in water. The theory is that viable, dense seeds will sink, while empty, non-viable seeds will float. However, this method is not foolproof and is not recommended as a definitive test by many experts.

Here’s how to do it:

1. Fill a clear glass with water.
2. Drop a handful of seeds into the water.
3. Wait for about 15 minutes.

While this can provide a general idea for larger seeds, numerous factors can cause viable seeds to float, such as trapped air pockets or the natural buoyancy of certain species. It is a fast first-pass check, but should not be the final word on your seed stock's fate. If seeds have been wet, you should plant the sinkers immediately as they will no longer be shelf-stable.

The Paper Towel Test: The Most Reliable at-Home Method

For a more accurate assessment of your seeds' viability, the paper towel test is the most widely recommended at-home method. It is essentially a small-scale germination test that gives you a clear germination percentage. It is also more versatile than the float test and works for seeds of all sizes.

Steps for the Paper Towel Test:

1. Gather 10 seeds of the same variety from your stash.
2. Moisten a paper towel until it is damp but not dripping wet.
3. Spread the 10 seeds evenly on one half of the paper towel.
4. Fold the other half over to cover the seeds.
5. Place the folded paper towel inside a plastic bag or an airtight container to retain moisture.
6. Keep the container in a warm, dark location, such as on top of a refrigerator or in a closet.
7. Check the seeds every few days for signs of sprouting. Germination times vary by seed type, so be patient. For some, it can take up to two weeks.
8. After the typical germination period, unroll the towel and count the number of seeds that have sprouted. If 8 out of 10 seeds sprouted, you have an 80% germination rate. This percentage indicates how many seeds you can expect to grow successfully when planted.

Seed Viability Comparison Table	Viability Test	Best For	Reliability	Time to Results	Pros	Cons
Visual Inspection	All seeds	Variable	Immediate	Quick, requires no tools	Can miss internal issues; healthy-looking seeds can still be bad
Float Test	Large, dense seeds (peas, beans)	Low to Medium	15+ minutes	Fast and simple	Not reliable; many viable seeds may float
Paper Towel Test	All seeds (especially smaller ones)	High	1-2 weeks	Accurate, simulates germination	Takes time, must be done well before planting
Soil Test	All seeds	High (most accurate)	Varies	Replicates real-world conditions	Requires more space and time

Preventing Bad Seeds: The Importance of Proper Storage

Many seeds lose their viability prematurely due to improper storage. To maximize the longevity of your seed stock, follow these storage guidelines:

• Keep them cool: Aim for storage temperatures between 40°F and 50°F (4°C - 10°C). A refrigerator or a cool, dark basement is ideal.
• Keep them dry: Moisture is the primary enemy of stored seeds. They should be completely dry before storage and kept in an airtight container to prevent humidity from causing mold or premature germination.
• Keep them dark: Light can damage seeds, so store them in opaque containers or a dark location.
• Use the right container: Airtight glass jars, such as mason jars, are excellent for long-term storage. For short-term use, sealed plastic bags or original paper packets inside a bigger airtight container also work well.
• Control humidity: Consider adding a desiccant, like food-grade silica gel packets, to your storage containers to absorb any lingering moisture.

The Downside of Using Bad Seeds

Planting non-viable or low-vigor seeds can lead to several problems in your garden, beyond just wasting space and resources:

• Uneven Germination: Some seeds may sprout while others don’t, leading to a spotty and uneven plant stand.
• Weak Plants: Even if they do sprout, plants from low-vigor seeds may be less robust, more susceptible to pests and diseases, and produce lower yields.
• Disease Spread: Diseased seeds can introduce pathogens into your soil, which can affect future plantings.

Conclusion

Identifying whether seeds are bad is a fundamental skill for any gardener looking to improve their success rate. While visual signs like discoloration and mold can offer hints, the paper towel germination test provides the most reliable at-home results. For the best outcome, combine a quick visual check with a germination test for older or questionable seed packets. Additionally, practicing proper seed storage in a cool, dark, and dry environment is the most effective way to prevent seeds from going bad in the first place, ensuring a thriving garden season after season. For deeper insights into seed testing protocols, institutions like NIAB provide more advanced information on assessing seed quality.

Frequently Asked Questions

Can I plant expired seeds?

Yes, but you should not rely on them. The date on a seed packet is a 'packed for' year, not a hard expiration date. Older seeds often have a lower germination rate, so you may need to plant more to achieve the desired number of plants.

Why did my seeds not germinate even after passing the float test?

The float test is unreliable. While a seed may be heavy enough to sink, it could still have a damaged embryo, internal deterioration, or simply have very low vigor. A germination test is a much more accurate predictor of success.

How should I store seeds to prevent them from going bad?

Store seeds in a cool (40-50°F), dark, and dry place. Use an airtight container, such as a glass jar, to protect them from humidity. For extra protection, you can add a desiccant pack.

What is a good germination rate?

For most vegetable seeds, a germination rate of 80% or higher is considered good. If your home test yields a lower rate, you can compensate by planting a few extra seeds to ensure a full crop.

What are the common signs of poor seed quality?

Beyond visual damage and low germination rates, poor seed quality can result in weak seedlings that are more susceptible to pests and diseases, and may not grow into healthy, productive plants.

Are older seeds more prone to disease?

Not necessarily, but improper storage that causes mold or rot is a common issue with older seeds. This can introduce fungal or bacterial pathogens that can harm future seedlings.

Is it better to buy fresh seeds every year?

For the highest possible germination rate and most vigorous plants, yes. However, properly stored seeds can last for years, with a gradually declining germination rate. Testing older seeds is a great way to avoid waste.