As anyone who has ever purchased seed packs knows, it is a pretty common thing to end up with a shoebox teaming with leftover packs. And it does not take long to accumulate a good selection of seeds from seasons gone by.

One way to make the most of these seeds is germination testing - a process that Sage Garden undertakes each fall and winter to evaluate current-season seeds and to help us plan for seed purchasing ahead of the spring growing season. The main process we use is to set an easy-to-observe quantity of seeds onto a filter paper in a petri dish, add water, close, label and wait. Each day the seeds get checked for germination, re-watered as necessary and the data recorded. At some point (exactly when depends on the variety), the test is deemed complete and the percentage of germinated seeds is compared to reference standards for the various species. For most seeds, germination rates are 85 - 100%, while for a few shy selections, good germination is rated as low as 55%.

Over the years we have noticed a few interesting things about this process. First, there are some seed types that germinate incredibly well in the petri dish but not so much in soil and vice versa. At times, we have found ourselves repeating tests on normally super reliable seeds only to get poor results... then test the same seed-lot in soil and get 100% germination. Some types of squash, cucumbers and beans have behaved this way. Another situation that comes up regularly is seeds that almost immediately go mouldy in a petri dish but germinate easily and without issue in organic potting soil. Examples include nasturtiums, calendula and watermelon. The speed at which some seeds germinate also varies depending on setting; we have seen seeds germinate in less than a day in the petri dish, while in soil the same selection may require 3 - 5 days to emerge.

In some cases, seeds may germinate much more reliably in soil, likely because the soil moisture can be more consistent but this also could be due to a requirement for darkness (some seeds require this - typically larger seeds that you would normally push well into the soil if sowing outdoors).

So, observing seed behaviour through germination testing has piqued our curiosity and changed the way we plan to do certain types of propagation. For one thing, in the greenhouse setting, we are often frustrated by erratically germinating seeds such as ultra-hot peppers and white sage. Traditionally, we started these in soil in 50 cell plug trays but found they would take up a lot of space over a long period, since the seeds may germinate over 4 - 6 weeks. For many of these selections, we moved to germinating them clustered in 4" pots in soil (which by the way seems to improve germination considerably, and a technique we call the Craig Lehoullier method), but there can still be a wide range of germination times and the seedlings end up at rather different stages but needing to be carefully separated before transplanting to plug trays. So, the petri dish method is really helpful to this situation, as we can in a small amount of space watch seeds germinate. And as each seed emerges it can easily be transferred to soil without disturbing the other seeds.

Another amazing thing about using the petri dishes for both germination testing and actually starting seeds is that if you are interested in watching how plants work, you get a very good view! For many seeds, as soon as you add water things start to happen. A fun example includes basil seeds, which develop a purple gel around the seeds within hours of being wetted, demonstrating that they have begun germinating (which is also why basil seeds are used like chia seeds in tropical drinks, similar to the "bubbles" in bubble tea).