How do you interpret germination rates?
Written by
Paul Reynolds
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Germination rates indicate the percentage of seeds likely to sprout within your garden. To find this figure, divide the number of seeds that have sprouted by the total number of seeds tested and multiply the answer by 100. For example, a germination rate of 90% means that 9 out of 10 seeds should grow. This percentage should directly influence your planting technique to achieve the best results.
Alter planting density according to germination rates. If your germination rates exceed 90%, you may sow at normal plant spacings. If your rate is 70%, then you must sow 1.5 times as many seeds as you would normally sow. If your averages are below 50% for any specific spot, you must replace your seeds or sow 2 to 3 times as much to achieve the desired density. I adjust my beans from year to year in accordance with my tests to avoid patches.
Perform this calculation correctly by following these steps: Count only sprouted seeds that have roots and shoots. Do not count moldy or otherwise disqualified seeds in your total. Do not take your final count for 48 hours after you have taken your last count of sprouted seeds. For tomatoes I test at least 20 seeds for statistical purposes. Record your results for future reference.
High Viability (90-100%)
- Planting density: Normal spacing
- Action: Sow seeds at recommended depth
- Example: 1 seed per inch for carrots
- Confidence: High success expected
Moderate Viability (50-89%)
- Planting density: 1.5x normal
- Action: Sow extras then thin seedlings
- Example: 15 bean seeds instead of 10
- Tip: Monitor germination closely
Low Viability (<50%)
- Planting density: 2-3x normal or replace
- Action: Heavy overplanting or new seeds
- Example: 30 lettuce seeds per foot
- Warning: High failure risk otherwise
Take seed type variations into account. Slow germinators, such as parsley, require longer observation periods. Quick germiners like radishes respond quickly. Always consider the optimum temperature for germination for every species. Your garden's influence on actual performance is compared to that in controlled conditions.
Use rates effectively for different planting methods, for seed trays, and increase cell density proportionately. For rows of seed plants closer together. I mark the seed packages with the rates determined by my test. It is a habit that helps me avoid mistakes when I plant in the spring, and enables me to get the most out of the garden each season.
Read the full article: Seed Viability Test Guide: Ensure Your Seeds Grow
