When turning off my seed-starting lights at night, I’ve been startled on more than one occasion by the appearance of my little charges. The leaves of some my plants droop like they are water-deprived. Over the years I’ve learned not to react because some of them are fakers. The leaves hang downward, but if you poke them, they are still very taut and strong.
This movement is called nyctinastic (night-induced). The seedlings know that day has turned to night and they are preparing to “sleep.” The behavior occurs even though my seedlings have no exposure to natural light. Even if I left my grow lights on all night, certain plants would still droop after sunset.
Not all of my seedling behave in this manner, but I can always count on the salvias and ageratums to give me a little scare now and then. I’ve learned to poke first before scrambling for the watering can.