Did you know a bit of magic is happening in your backyard? Pine trees perform a fascinating feat every time they get wet! So the next time you are out for a hike, take a closer look at a pine cone.
Pine trees disperse their seeds by opening their cones and allowing the seed to fall. For the best germination and survivability, the seed must float and fall far away from the original tree. Pine seeds do not travel far in wet conditions.
Basically, pine tree cones close when wet so seeds can wait for drier weather.
Pinecones function primarily for reproduction, one of the most critical tasks for any plant. They open and close to protect seeds from a variety of factors, not just water! Read on to learn more about why this happens!
As noted above, a pinecone’s primary function is reproduction. Pinecones protect the developing seeds and sometimes aid in dispersing seeds.
A young pine cone, once fertilized, begins to harden and grow in size. Pine trees can take two years for the seeds to mature within the cone. When the seeds have matured inside the pinecone, it opens, and the seeds are dispersed into the air, eventually falling to the ground.
It is in the tree’s best interest that its seeds fall from the pinecone and drift far away from the original tree. If the seed fell too close to the original tree, it would struggle to germinate. Furthermore, if germination did occur, that new tree would struggle to compete for sunlight and nutrients with the mature tree.
What Does It Mean When Pine Trees Close?
Pine trees close their pinecones to protect the developing seeds during specific weather situations. Whether that induces pinecone closings are freezing temperatures, unseasonably cold weather, rain, and humidity.
Additionally, pinecones may close during specific times during their reproductive cycle, for example, releasing and receiving pollen and seed dispersal.
When the weather is wet or humid, the seeds will not float or drift with the wind, but fall quickly to the ground where they have little chance of reaching maturity. This is why a pine cone closes when it gets wet. It protects the seeds from falling too close to the tree.
Not all pine cones close when wet. To know if your pine tree has cones that exhibit this unique ability, consider purchasing The Tree Identification Book: A New Method For The Practical Identification and Recognition of Trees to better understand the pine trees in your backyard.
Water Swells Pine Cones And Needles, Causing Them To Close
The science behind this phenomenon is still being understood at the cellular level. It boils down to two different types of cells, arranged in two layers that flex when exposed to moisture. This process is more complex than just water swelling the parts of the cone.
Scientists believe that understanding how a pinecone opens and closes with moisture could help us develop better water movement techniques to help grow food or fight climate change.
Cold Weather Causes Cones To Close
In addition to closing during rain and humidity, pinecones stay closed through the winter and during unseasonably cool summer weather.
The pine tree seeds are housed inside the pinecone, and it is the cone’s job to protect the seeds. Therefore, pine cones stay closed through the winter to protect the developing seed. Since winter is not an ideal time for seed dispersal and germination, the pine cone remains closed.
For more info, read our article on how to care for your pine tree over the winter season.
Closing Cones In Cold and Wet Weather Helps For Reproduction
The primary function of pinecones on trees is for reproduction. In pine trees, there are male and female cone structures.
The male cones release pollen into the air, while the female cones are designed to collect pollen and siphon it toward a seed for fertilization.
Once the male-structured pinecone releases its pollen, it has done its work and falls from the tree. Once fertilized, female pinecones begin to harden into the woody structures, we know as pinecones.
Female Pine Cones Open And Close Throughout Their Life Cycle
Female pinecones open and close throughout their life during essential times in the reproductive cycle. When the cone is young, its scales open just as trees begin to release their pollen. The wind carries the pollen to the female pinecone and enters through the slightly separated scales.
Between the cone scales, the pollen is directed to the ovum, where it is fertilized. Next, the seed begins developing. At this point, the pinecone enlarges, and the scales close tightly to protect the developing seed.
Depending on the species, the seed may take up to three years to mature. Once the seed has matured, if conditions are right, the scales open, and the seeds are dispersed in the wind.
Different types of pine trees have other seed-releasing mechanisms. Some pine cones only open in the presence of fire. These trees need fire to complete their reproductive cycle.
Waiting until a fire releases seeds gives these pine trees an advantage, as they will get a head start on growing without competing with dense underbrush.
Weather Is Cold Or Stormy When Pine Trees Close
Pinecones close when the weather is cold because they do not want to release their seeds into an environment that isn’t ideal for germination. Since seed germination happens during warm temperatures, pine cones keep their seeds protected through freezing weather.
If a seed is released when it is too cold, it will not germinate or grow into a tree.
Additionally, pinecones do not release their seeds during a storm. Therefore, the best scenario for a pine tree is to remove its seed on a warm and dry day so that the seed can travel on the wind a great distance.
If the seed is released during a storm, the water and humidity will cause it to fall directly under the tree, where it cannot survive.
If you are still curious about how your pine tree will weather dark, dreary days, we have you covered with our article on how much sunlight a pine tree actually needs.
Pine Trees May Be In Their Reproductive Cycles When Opening And Closing
As discussed above, seed dispersion is a part of the reproductive cycle. There are additional times during the life cycle of a pine cone when it may open and close. A young female pine cone first opens during pollination to allow pollen, carried by the wind, to fall between its scales and pollinate an egg.
After the egg is pollinated, the cone scales begin to harden and enlarge to protect the seed as it develops. The pinecone won’t open again until the seed has matured and is ready for dispersal.
Is It Okay For Pine Trees To Close When Wet?
Yes! Not only is it okay for pinecones to close when wet, but it’s also an essential part of their reproductive cycle!
Pinecones close when wet to protect their seeds. Seeds need warm and dry weather to ensure maximum survivability.
The motion of the pinecone closing and opening with weather changes does not hurt the tree. On the contrary, it is a natural adaptation to ensure the tree can produce offspring.
Keeping Pine Cones Open
You won’t be able to control the opening and closing of pinecones on a living tree. That happens naturally and is a process that shouldn’t be interrupted.
If you have pine cones you want to keep open for crafting or decoration, keep the pine cones in a warm and dry location. They will remain available for as long as you need if you keep them dry.
Some Pine Trees Only Open With Fire
The jack pine, native to the north-central United States and Canada, requires fire to open up its pinecone and release the seeds. A thick layer of resin covers the cone that must melt before the cone can open up.
As the fire moves through the forest, the cones of the jake pine tree open up, and the wind disperses the seeds. The fire method has some advantages for the jack pine that now has fresh ground to grow in, free from competing weeds.
Sometimes, forest management includes controlled burning, the process of burning out the underbrush in a mature forest or prairie. Controlled burning ensures that plants like the jack pine tree can be around for centuries to come. In addition, this small fire puts nutrients back into the soil and keeps invasive plants and pesky underbrush under control.
Pine Trees Closing Helps Them Create More Offspring
When a pinecone closes its scales, it protects the seeds that lie within from extreme weather conditions. This protection ensures that as many seeds as possible reach maturity, are released from the cone, and land gently in the perfect area for germination and later tree growth.
If the tree did not close its pine cones during wet weather, its seeds would not be protected. Instead, they would be susceptible to bacteria and fungi, preventing them from reaching maturity and potential germination.
Pine Trees Closing Can Protect Them From Predators
Birds are common predators of pine trees. Long-billed birds can pluck the seeds from between the available scales. When a pine cone is closed, the bird’s beak is not strong enough to break through the scales to get to the seeds. So, another example of the great job pinecones does is protect seeds!
Some species of pine trees have rigid spines on their woody scales. As the scales open and close, these spines hinder and prevent birds from getting at the seeds. When a pine cone is open, its seeds may be in danger, but a pinecone with scales makes predation even more difficult.
Try It At Home!
You can do a fun experiment at home with the pinecones you find in your neighborhood. Place a few in a bucket full of water, and leave a few in the dry open air. If you watch the cone in the water closely, you will see it slowly close until all the scales are tightly packed.
The cone that remains dry will not change. It will stay open. Now take the wet pinecone out of the water and place it next to the dry one. As it dries, it will slowly re-open. How long did it take your cone to reopen?
What To Do If Your Pine Trees Close When Wet
If you notice your pine trees close when wet, don’t worry, this is an entirely natural and important reproductive mechanism for the pine tree.
Unless you use fallen pinecones for a craft project, leaving your pine trees alone is the best course of action if you notice they are wet.
If you have young experimenters who would like to learn more about how pine trees grow from pine cones, “How Do Pine Trees Grow?” is the perfect early reading book.
You could also read our Full Pine Tree Timeline for more information on pine trees and how long they take to grow.
Wait For Your Weather To Get Better
Pinecones with mature seeds will reopen when wet and humid weather has passed, so they can continue releasing the seeds in the wind. The best conditions for pine cones to be open are warm and dry with a light breeze.
Pinecones with immature seeds will remain closed to protect the seeds from fungus and predation, no matter the weather. So leave them alone to let them do their thing!
Move Harvested Cones To A Dry Location
When collecting pinecones for crafting or decoration, it is best to harvest only the pinecones that have fallen to the ground, so you don’t interrupt the tree’s reproductive cycle.
Collect fallen pine cones when the cone’s scales are open during wet and dry weather. Store the pinecones in a warm and dry location to keep them open.
If your pinecones accidentally get wet, move them to a dry place. They will reopen once they are dry.
Are you hoping to use pinecones in your holiday decorations this year but don’t have a pine tree nearby? Then, purchase 20 Pine Cones 3″ to 4” Tall Bulk Packages for all your festive needs!
For other pine project ideas, our article on what to do with pine trees with over 21 uses!
That’s A Wrap!
The pinecone’s primary purpose is reproduction and seed protection. Weather changes and reproductive seasons will open and close the pinecone scales.
A pinecone opens and closes for:
- Seed protection from predators
- Seed protection from poor weather
- Seed fertilization
- Seed dispersal
The next time you come across a fallen pine cone, consider picking it up, bringing it home, and placing it in a glass of water. You just may get to see this fascinating phenomenon in action!
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Eger, C. J., Horstmann, M., Poppinga, S., Sachse, R., Thierer, R., Nestle, N., … & Rühe, J. (2022). The Structural and Mechanical Basis for Passive‐Hydraulic Pine Cone Actuation. Advanced Science, 2200458.
Leslie, A. B., & Losada, J. M. (2019). Reproductive ontogeny and the evolution of morphological diversity in conifers and other plants. Integrative and comparative biology, 59(3), 548-558.
Losada, J. M., Blanco‐Moure, N., & Leslie, A. B. (2019). Not all ‘pine cones’ flex: functional trade‐offs and the evolution of seed release mechanisms. New Phytologist, 222(1), 396-407.
Quan, H., Pirosa, A., Yang, W., Ritchie, R. O., & Meyers, M. A. (2021). Hydration-induced reversible deformation of the pine cone. Acta Biomaterialia, 128, 370-383
Song, K., Yeom, E., Seo, SJ. et al. Journey of water in pine cones. Sci Rep 5, 9963 (2015).
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