The article about Impatiens mentions placing two seeds in each cell. Will they not sprout if sown individually?
Single Seed or Two?
Certified GKH Gardening Expert
They will sprout if sown individually. The only real reason for placing multiple seeds in each cell is to ensure every cell produces as you may encounter some seeds that fail to germinate. Also, multiple seeds in a cell gives you the opportunity later to thin them (if you so desire) to allow only the most vigorous seedling to grow.
For more information on impatiens seed propagation, please visit the following link: