At the California Seed Bank at RSABG, we conduct germination tests on agar and use 4.5″ x 4.5″ square plastic plates. They are reusable and last for a very long time. We use BD Difco Granulated Agar. Before plating seeds on agar, we dip them in a 20% bleach and 1% Tween 80 (a surfactant) solution for 1 minute. After the bleach and tween (BLT) treatment we sow the seeds directly on agar. Push the seeds into the agar a bit so they stay put, otherwise they will move around on the agar surface. The BLT helps control the growth of microbes, but doesn’t completely supress it, so sometimes we need to retreat the seeds and sow them on a fresh plate. The BLT can also damage the seeds, so sometimes it’s a bit of a judgement call between letting the mold get to the seeds and over-bleaching them. We label the test by writing directlty on the plate with sharpie, which can later be removed with alcohol.