When you mix varieties in the same cell pack then cutting them apart is the only option. You can't leave the germinated ones on the heat or under the dome as you risk killing them while waiting for some that may never germinate any way.

The beat bet is you don't mix varieties in the same cell pack. Actually the ideal is you never use cell packs for germination anyway. They aren't intended for that use but the manufacturers mislead people into thinking they are to sell them. You germinate in bulk in separate small containers - shallow pots, trays, cups, etc. and then transplant them into the cell packs.

Now if they are all the same variety by the time the first few have germinated the rest will either follow shortly or would never have germinated anyway.

Dave

For the tomatoes, I didn't mix varieties within a 6-pack. I have 14 varieties and since sixteen 6-packs will fit in two flats, two varieties have two 6-packs while all the others have one 6-pack.

Thenâ¦â¦â¦.as Dave says, as soon as even one seed in a cell pack sprouts, remove it from the heat and get it under lights, the rest will follow. While heat mats may speed it up, many many people germinate tomatoes without them.