I planted regular impatiens in a place which is mostly shady, but I'm not getting any flowers. What's wrong?

They get enough water, but they're not producing any blooms. The leaves look a little pale to me. I bought them from an individual who had them in a flat-type tray. I thought that they might be root-bound, so when I planted them, I loosened up the roots. Still no improvement. Any help would be appreciated. Thank you.