To really understand when a plant is ready to make the move outside I experimented. I am growing MoonFlower at the base of the Japanese Lilac I have been following through the seasons (below).

Oh, and I left out my seedlings all day in the sun and all night (down to 3 degrees) and they appear to be fine - so I guess they are officially hardened off enough. It was not as much work as I had thought and I am thrilled with how many plants I have for the money.
Now to plant them and see how they adapt to the garden...clear my schedule!
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Sharing with Fertilizer Friday