It takes impatiens about 8-10 weeks to flower from sowing under good conditions, but the seeds require almost continously warm soil around 60-70 deg F to germinate. If direct sowed outdoors, you can probably not see germination until late may and that would give you flowers by early august, if you are lucky. Direct sown impatiens may be suitable for zones where germination temperatures are present in february and you have entire growing season until november, but for zone6 it is not worth it.