What are the Common causes for impatient stunting ?

[brooklyn boy]

I grow my inpatients in the dark and when the seedlings pop out I transfer them to the window sill and it stops growing what am I doing wrong???

[pow wow]

I grow my impatient seedlings under artificial light. And when I move them into my greenhouse I keep them out of direct sunlight.

[applestar]

Yes, my thought was that either the windowsill's direct sun is too strong, or that the windowsill is too cold.

[brooklyn boy]

Yes, my thought was that either the windowsill's direct sun is too strong, or that the windowsill is too cold.

should I avoid the sun altogether and put them on a counter that's close to a window ?

[applestar]

What you may need to do is "harden off" -- acclimate the seedlings gradually.
You could START by putting them further inside the room then moving them closer to the windowsill. But I would want to give sprouting seedlings good strong light. Otherwise they would get spindly.

I think I would rather put something on the window -- a vellum paper or gauzy fabric, sheer or lace curtain, etc. experiment with maybe 60%-80% light. an open weave type material like wicker or lace partially blocks the sun in a dappled effect like under a tree. You could "acclimate" by blocking more light initially but gradually allowing more light.

Is your window insulated/double-panes or is it drafty? Temperature maybe a moot issue after this weekend if there are no more frosty temps in the forecast. But I would put a thermometer there to monitor the temps. If you suspect it is drafty, you could tape the gaps where the seedlings go. You could also take them off the windowsill when extra cold overnight temp is in the forecast. If you are drawing curtains/drapes over them at night, you could be trapping cold air between the window and the window treatment.