Germination Rates - What Do They Actually Mean?
If you’ve ever been flipping through a seed catalog and wondered what the term germination rate actually means, you’re not alone. Read on to learn more about what seed germination rates represent and even how to do an at-home germination test!
What is germination rate?
All that a germination rate signifies is the average number of seeds that will sprout given a specific amount of time. Germination rate is calculated by dividing the number of seeds that sprout by the total number of seeds started, and then multiplying that number by 100 to get a percentage. For example–if you were to start ten seeds and eight of the seeds actually sprouted, you would have a germination rate of 80%.
Ideal germination rates
The higher the germination rate the better, with a percentage of 80 or above being preferred. The higher the number, the more of your seeds will sprout, meaning you’ll spend less money on seeds and materials, and you won’t waste any time waiting on lifeless seeds to sprout.
Low germination rates
If your seeds have a lower germination rate, be prepared to sow more seeds to get the same number of plants–if your seeds scored only 50% germination, plant two seeds and expect to get one seedling from each pair. If your seeds are 75% viable, expect that for every four seeds you sow only three seedlings will sprout.
You’ll also want to start seeds with low germination rates sooner than seeds with higher germination rates. Lower-germination seeds need extra time to sprout, and starting these seeds early gives the gardener plenty of time to sow another batch of seeds if the results aren’t satisfactory.
How to find germination rate
Germination rate for any particular variety isn’t always easy to find. While most seed packets will list statistics like days to maturity, ideal temperature, plant spacing, and lighting requirements, you usually have to do a bit of digging to find out the germination rate for a batch of seeds.
Most seed packets will have a Lot number on the packet, so if you’re curious you can reach out to the seed company with the information listed on your seed packet and find out exactly what the germination rate is for that particular batch of seeds.
You can also send off your seeds to a university or agricultural extension office to have professionals test your seeds. This is particularly helpful for gardeners and growers who have saved their own seeds and want to know exactly how viable their seeds are.
Or, you can very easily do an at-home germ test and find out the numbers for yourself–while learning about seed germination in the process.
Paper towel germination test
To do a simple germ test, decide which seeds you want to test. Most people test between five and ten seeds and get fairly accurate results, but the more seeds you test the more precise your results will be. Check out this guide to at-home germination testing by Seed Savers Exchange for more detailed information.¹
To germ test your seeds, moisen a couple of paper towels and lay them out flat. Place your seeds evenly on one side, then gently fold the paper towels in half so that the seeds are covered on both sides. Transfer to a gallon-size Ziploc bag but don’t seal it shut.
Keep the bag in a sunny location, and check the paper towel frequently, adding water if the paper towel begins to dry out. Use the recommended days to germination listed on the seed packet as a guide to know when to expect the seeds to sprout. After the germination window has passed, count up the number of seeds that have sprouted and divide that number by the total seeds used in the test. Multiply that number by 100 to get a percentage that is your germination rate!
What factors affect germination rates?
There are a number of external factors that determine whether or not seeds germinate. When testing seeds for sample germination rates and when sowing seeds for optimal germination, you’ll want to create an ideal environment for seeds to sprout.
Age of the seeds
Even the highest-quality seeds lose viability with age. It’s why seed packets always have a packed for and sell by date. That’s not to say that seeds expire–most seeds, if stored properly, will still have excellent germination two years after purchase. Some seeds will still sprout three to five years after their packed-for date, but germination will decrease each year that seeds aren’t used.
How the seeds were stored
Seeds that were prematurely exposed to moisture, warmth or light won’t have as high germination rates as those seeds that were stored correctly. If you’re not using your seeds immediately, the seeds should be stored in a cool, dry, and dark place. Keep your seed packets and loose seeds in Ziploc bags, plastic containers with lids, or even mason jars. Minimize exposure to condensation, humidity, light, and heat by keeping seeds in airtight containers in a cool room that doesn’t see the sun.
Whether or not the seed was prepared
Some seeds–more so perennial flower seeds than annual vegetable seeds–require either cold stratification, scarification, or pre-soaking to germinate. Cold stratification involves refrigerating the seeds to mimic winter conditions. Scarification is the process of roughing up the seed coat to allow water to permeate the seed coating and break dormancy. Pre-soaking seeds is helpful with beans, peas and legumes–the seeds absorb water, swelling twice their size, and jumpstarting the germination process.
Ways to increase germination rates
Even if your seeds had a lower germination than expected, there are ways to get the most out of the remaining viable seeds. For more information on starting seeds indoors, check out this article on seed-sowing hacks.
Seeds require even moisture to germinate. Start seeds in soil that is moist but not overly wet, and keep the soil moist until the seeds germinate.
Seeds, just like seedlings and mature plants, need to be able to breathe. Sow seeds in a porous growing medium that allows the exchange of airflow between the seeds and their environment.
Soil temperature has a massive impact on seed germination rates. The University of California has found that while there are a range of temperatures at which most vegetables will germinate, certain species sprout exponentially at their ideal temperatures. According to this study, while lettuce might take two weeks to germinate at 40℉, those same seeds will germinate in less than three days at 77℉!²
Most annual vegetable seeds germinate in soil temperatures ranging from 70℉ to 80℉. Cool-season crops like radishes and onions will germinate in cooler temperatures, but reference UCA’s Garden Notes chart to find temperature needs for your seeds, and use a heat mat and thermostat to achieve the ideal temperature.
Some of the smallest seeds, particularly wildflower seeds, actually need some light to germinate. If a variety calls for light to germinate, don’t bury the seeds too deep–instead, sow the seeds on the surface of the soil and dust with sand to keep the seeds in place.
A good rule of (green) thumb is to plant seeds twice as deep as they are wide. Any deeper and some seeds won’t sprout, but sow too shallow and the seeds might wash away at the next watering.
Don’t let germination rates throw you off–all they really are is a shorthand for communicating how viable a batch of seeds are. Germination rates are directly connected to seed age and quality, and at Seeds ‘N Such we strive to always provide our customers with the highest-quality, youngest seeds so that germination rates are the last thing you have to worry about when starting your own flowers and vegetables at home.
¹ Home Germination Testing. Seed Savers Exchange, https://www.seedsavers.org/site/pdf/HomeGermTests_LAFrevised.pdf.² Pothour, Gail. Soil Temperatures Conditions for Vegetable Seed Germination. Edited by Judy McClure. University of California, February 2013, https://sacmg.ucanr.edu/files/164220.pdf.