Gardening
Landscaping
Lawn Care
What impacts the viability of grass seed
By
David Beaulieu
:max_bytes(150000):strip_icc()/headshots_FINAL_david-beaulieu-d92b82a50a3348a39241022715db70ff.png "Stored Properly, Grass Seed May Stay Viable for up to 5 Years (1)")
David Beaulieu
David Beaulieu is a landscaping expert and plant photographer, with 20 years of experience.
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Updated on 04/16/24
Fact checked by
Jessica Wrubel
:max_bytes(150000):strip_icc()/NewheadshotJW-931b8aadf3d540ccb600a4d03b1276a9.jpg "Stored Properly, Grass Seed May Stay Viable for up to 5 Years (2)")
Fact checked byJessica Wrubel
Jessica Wrubel has an accomplished background as a writer and copy editor, working for various publications, newspapers and in public libraries assisting with reference, research and special projects. In addition to her journalism experience, she has been educating on health and wellness topics for over 15 years in and outside of the classroom.
Learn more about The Spruce'sEditorial Process
:max_bytes(150000):strip_icc()/GettyImages-519977770-5a9646281d640400377d6322.jpg "Stored Properly, Grass Seed May Stay Viable for up to 5 Years (3)")
In This Article
Germination Rates
Ideal Storage Conditions
Recommendations
FAQ
Many homeowners keep a large bag of grass seed in the garage or shed to have on hand whenever a patch of bare lawn needs to be reseeded. But you may well wonder if that old grass seed is still viable, or if it has gone bad with age.If you store high-quality grass seed in ideal conditions that are dry and cool, you can count on the germination rates dropping 10% each year. Read on to learn how to tell if your grass seed is expired, tips to store it to make it last the longest, and the best way to use older grass seed.
The Viability of Grass Seeds
Germination rates vary considerably by plant, and it also depends on how the seeds are stored. To check your specific grass variety, the germination rate is stated on the grass seed package. New grass seeds starting with an 80% germination rate—declining 10% yearly when stored in cool, dry conditions—will have a 50% germination rate after three years.
Factors Affecting Seed Viability
The viability of stored seeds of any kind are greatly influenced by storage conditions, and unfortunately, the ideal conditions for seed storage are very often exactly the opposite of how homeowners store grass seed. In general, seeds will maintain their viability longest if stored in cool, dry conditions—which is not the condition typical in most garages and sheds. The factors influencing seed viability include:
- Seed moisture. An internal seed moisture level of 10 to 20% is ideal for most seeds. Seeds that lose moisture andfall below this level, or absorb humidity to higher levels, are likely to die.
- Storage temperature. Ideal storage temperatures for most seeds are above freezing but under 60 degrees Fahrenheit. Temperature above 100 degrees can badly affect seed viability.
- Storage humidity. If seeds are stored in cloth sacks or open containers, their moisture levels are subject to change. In humid climates, they may absorb humidity.
Recommendations
There is no harm in trying to use some old grass seed for top seeding or reseeding, but you should expect there to be a lower germination rate than you would enjoy with fresh turfgrass seed. To compensate for the lower germination rate, use more grass seed than recommended to make up the difference. A box or bag of grass seed that has been stored in very warm conditions, or open to humid summer air, will not hold its viability very well.
For the future, your new grass seed will keepbest if you store it in a tightly sealed plastic bag or container so it cannot absorb moisture. You can extend its viability by keeping it out of a hot garage or shed and storing it indoors where it is cool.
The cooler the storage temperature and the dryer the relative humidity (RH), the longer your seeds will remain viable. Seeds stored in a sealed container in a refrigerator usually enjoy the best longevity. If this isn't practical, seek out the coolest location in your home. Stored with this kind of care, your grass seed may remain viable for as long as five years.
FAQ
How can you tell if grass seed has gone bad?
There are several ways to tell if your grass seed is still viable. First, inspect your grass seed, it should be uniform in color, smell fresh, and have a firm, whole appearance. Old seeds may smell musty and feel lighter than viable seeds. For a quick test, float a handful of grass seeds in a glass or bowl of water, if more than 80% float, the seeds are likely expired. For a more accurate test, plant 100 grass seeds on a paper plate covered with moist soil. Cover the plate with plastic wrap and keep it in a sunny spot. Mist the soil daily with water. After a week, if you count more than 80 seeds with sprouts, your grass seed is viable.
How long does grass seed last?
Grass seed germination rates decline within two to three years, but when kept in ideal conditions, it can still be viable for up to five years. Store grass seed in a sealed container in the driest, coolest spot in your home.
When is the best time to overseed a lawn?
The best time to overseed a lawn for most USDA growing zones is early spring, from mid-February to mid-April, and late summer, from mid-August to the end of September. Although the timing can vary depending on your USDA growing zone and the type of grass you're planting, ideal temperatures for seed germination are between 50 and 60 degrees Fahrenheit.
