Are seeds dead if they float?

If your pumpkin seeds smell or taste rancid, stale, a little sour, or just not like they used to be, discard them. Rancidity doesn’t mean the seeds are no longer safe to eat, but the nutritional value may decrease, plus rancid seeds taste bad.

One method to verify the viability of seeds is the water test. Take the seeds and place them in a container of water. Let the seeds rest for 15 minutes. If the seeds sink, they are still viable; if they float, discard them, as they likely won’t sprout.

Seed Viability Science Using the Water Float Test

Acorns have very low germinability because many seeds do not fully develop inside the nut and because various parasites lay their eggs in viable seeds which are subsequently eaten by the larvae. Floating them is a common way to get rid of many of the non-viable seeds. Even with this test, too much agitation of the water will cause viable seeds to float.

Juniperus polycarpos, the Persian juniper, also produces a low number of viable seeds. Floating in water isn’t a reliable means of separating the good from the bad, but floating in a sugary solution does work. Sugar water has a higher density than water, and this difference can be used for separate seeds of various densities. The heaviest vital seed sinks.

The Process

Since this blog is all about pepper plants, I’m sure it’s no big surprise that I’m using pepper seeds for the test.

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Step one: all the seeds were placed in cups of room temperature water and then stirred quickly to encourage them to sink.


If the coating on a seed is thinner than usual, brittle or flakes off, it is likely that the seed is old and no longer viable. A healthy seed, on the other hand, will have a waxy sheen to its coating. A sign that it is healthy and still viable for germination.

A healthy grass seed should be plump and firm to the touch. A seed that is shriveled or looks hollow is old or has not formed properly before harvest.


  • How to test seeds
  • Frequently Asked Questions
  • Resources
  • Place 10 seeds on a moistened (but not dripping) paper towel in an open container in a dark, warm cupboard for the expected number of days to germinate (or a little longer).
  • Check seeds daily for changes and moisten a paper towel as needed.

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