This year, my youngest gardener has chosen to test the effect of soil temperature on seed germination. I already have my theory, based on book knowledge, and I do start seeds with heat mats. So, it will be interesting to see if starting seeds with pre-warmed soil, soil that warms over time, or basement temperature soil makes a difference. Now, to find viable seeds already – thinking marigolds, radishes, and basil all start quickly but seeds are not yet in the stores locally. Will have to go through my inventory of seeds. I regularly re-use seeds from last year or even the year before with good results – I just sow a little heavier and then tweeze out the extras. But, does that throw off the data? Do I need to make sure all seeds are equally old?