Basic Question on Growing Under Lights

This winter I'll be growing three types of perennials from seed, in 72-cell flats, to plant in the spring (Nepeta nervosa, bee balm, and creeping thyme.)

Is it always a good idea to plant two seeds per cell and then thin the weaker plant? Or does this only make sense with certain species?

Thank you!

Hoping to see an answer on this, as I am wondering the same thing.

If your seed supply allows, it makes sense to plant two, and in some cases more, seeds per cell and then thin to the strongest seedling. Not all of the seeds will germinate, and this is also insurance against having empty cells.

Do the thinning fairly quickly, because you don't want them competing against each other in a cell. Because they have the same nutritive requirements, a plant species is its own worst weed. To avoid disturbing a nearby seedling in the cell, I use small sharp-pointed scissors to snip a seedling off at the surface, rather than pull it out and possibly damage the root system of a nearby seedling in the cell. Actually, I start my zinnia seedlings in tiny pots, but the principle is the same.

ZM

There is no one right answer to this. It depends on what's more important to you. Is it more important to make sure every last cell has a plant in it? Then plant multiple seeds per cell.

Is it more important to get every last plant out of the seed that you have? In that case plant one seed per cell and accept that you'll have empty cells.

One place I would recommend against planting multiple seeds in a cell and eliminating the weaker one is with mixes. There is no guarantee that color or other characteristic that you are looking for isn't tied to growth rate. In other words the prettiest flowers might come from the weakest seedlings. I don't thing that applies to way you have listed.

You could actually save yourself some effort with potting-on (assuming you will grow the seedlings on to a good size prior to planting out?) if you start your seeds in larger pots - the 4" pots that one acquires from buying plants work very well. They can also often be had for free at the nurseries, where they are being discarded or recycled. Using larger pots will, needless to say, take up more room, but it's room that start to be taken up quickly anyway, as the seeds germinate, and then soon need to be potted on.