I keep my seeds stock current. There is no guarantee on the seed germination because seed germination doesn't depend on seeds quality only. they require user experience, perfect temperature, proper watering. so i am selling my seeds as is with no guarantee. 
600+ Early purple Vienna Kohlrabi Seeds, NON-GMO. Fresh seeds.

Kohlrabi is a cool season crop grown similarly to cabbage able to be sown direct in early spring or early fall. For earliest starts, begin indoors 3-4 weeks prior to frost dates. Plant 3-4 seeds 1/2" deep per cell or 3-4" apart in the garden in Organically rich, loamy, and well-drained soil with a pH of 6.0-7.5. Seeds germinate in 3-10 days, thinning out best starts to 1 plant every 12-15" in the garden as true leaves establish. Kohlrabi does not do well in containers. A thin layer of top mulch helps retain moisture and cool roots during warm summer months.