Answer: I would not try to set out most of your mentioned plants before the end of April. We can still get a frosty night, even in New York city, until then. The exception would be sweet peas and snapdragons. These can take a light frost and survive, so perhaps put these out a few weeks earlier. The sweet peas and nasturiums should be direct sown in the soil outdoors. The coleus and impatiens should be started about 10 weeks earlier indoors under lights. The thunbergia and snapdragons can be started about 6-8 weeks before the last frost date in the same way and then transplanted out into the garden.
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