Do Tulips Close at Night?

Many flowers are known to retire for the night but does it apply to tulips?

Absolutely. Just like many other flowers, tulips too close up at night, a behavior scientists have christened nyctinasty. Triggered by low temperatures and darkness, the behavior causes rapid growth in the lowest petals of tulips, effectively forcing the flowers to close up.

It’s not yet clear why tulips do this but scientists have come up with a few theories which we’ll be looking at in a few. For now, here’s a deep dive into the whole process of nyctinasty.

Understanding Nyctinasty

Nyctinasty is controlled by a blue-green pigment called the phytochrome which, by the kind of light it absorbs, influences the type of growth and development a plant can undergo.

The kind of light, in this case, refers to red and far-red lights, found in the visible spectrum of the larger electromagnetic spectrum. Each of the lights here occurs during different times of the day with the red being available during the day while the far-red is more detectable as the sun goes down.

By detecting each of these lights, phytochrome helps plants like tulips establish a sleep-wake cycle – red light means it’s time to open up while far-red is a sign to close down shop for the night. The actual opening and closing are then effected by the pulvinus which acts basically as a motor organ.

In some plant parts, though, the closing up can also happen without the involvement of the pulvini. The motor organ in this case is replaced by the movement of water in and out of the plant cells.

Besides nightfall, tulips and other plants that exhibit Nyctinasty close up on rainy days.

Why Do Tulips Close at Night?

This is a big question in the scientific community. And despite years of deliberation, it still remains unanswered to this day.

That being said, we have a few theories trying to explain the phenomenon. Let’s take a look.

Defense Against Nocturnal Predators

There are always animals looking for a midnight plant-based snack, and tulips are on the lookout to not be the ones on the menu – at least that’s what some scientists think. Closing up just makes it difficult for animals like bats, beetles, and moths to have a bite.

That’s one version of the theory.

Another version of how tulips use nyctinasty for protection against predators is that it provides a clear view of the ground for night hunters like owls. That way, these predators can easily spot the herbivores who might be looking to feed on the leaves or flowers.

Energy Conservation

Tulips, pretty much like any flowering plant, depend on mostly insects for pollination. And these insects are active during the day, drawn to the magnificent blooms by the bright colors.

While it might not look like much of a task to us, keeping the flowers open is quite taxing to the tulips. During the day, it makes sense since there’s the possibility of pollination. At night, though, there’s really no need for it because, as mentioned, the insects have retired, and they couldn’t possibly see the blooms anyway.

So it’s best to fold up a bit as the night approaches to keep some energy when the light comes back again the next day.

Reduce the Risk of Freezing

This theory was put forward by the father of evolution himself, Charles Darwin.

Turns out – plants are just at the risk of freezing to death as animals. The only difference is that they can’t move in search of warmer places, so they have to get a bit creative. Closing up for the night is apparently the plants’ way of doing this seeing as it also helps keep most of the energy to themselves.

This is especially true for flowers as they tend to be warmer than leaves on average at night as you can see in these photos.

Keeping Pollen Grains Dry and Light

Wet pollen grains are bad for flowering plants like tulips because they become a.) unviable and b.) harder to move – especially for tulips that depend on wind pollination.

Closing the blooms at the end of the day keeps the pollen free from dew.

Final Thoughts

Tulips, like a few other plants close at night, a process that’s referred to as nyctinasty. While scientists understand the mechanism behind it, the specific reasons behind still remain a mystery.

According to a few theories, it’s mainly about protection – from predators, energy loss, freezing temperatures, and dew.