You’re most likely familiar with leaves falling off of certain trees when the weather starts to get cold–it marks the beginning of fall and signals an end to the warm weather. But have you ever wondered why leaves do this?
Falling leaves are just a small piece of a larger process called dormancy, which is a vital and necessary part of a tree’s life. And although it’s the most obvious signal of dormancy, there’s more to entering dormancy for a tree than just the leaves turning bright colors and falling off. Keep on reading to fully understand what dormancy means for your plants.
The best way to think of a tree in dormancy is to compare it to a bear in hibernation. Just as the bear needs rest during the winter and wakes up in spring, so does the tree. The process of dormancy is equally about survival as it is about energy conservation when wintertime resources are scarce. The bear is conserving energy and protecting itself when the weather conditions are too harsh in a similar way that the tree does. It just looks a bit different.
Trees spend spring and summer harvesting energy and expending that energy to grow shoots, leaves, flowers and fruits. As the days get shorter and the sunlight dwindles, trees enter into dormancy or an “energy saving mode.” There are changes internally and externally that happen to the tree when this time comes.
Internal changes during dormancy are occurring at the same time that the external changes are. Just because you can’t see the internal changes doesn't mean they aren't as important–they might even be more important than the external changes!
Here’s some internal changes that occur:
- Growth dramatically slows or stops
- Signals are sent to the leaves to stop harvesting energy
- Sap will continue to flow, acting like antifreeze inside the tree & preventing damage
External changes are the most obvious to us when checking to see if a tree is entering dormancy or not. These are the visible changes we see on the outside of a tree.
Here’s some external changes that occur:
- The green pigment responsible for energy production from the sun will start to fade, revealing the red and purple pigments underneath that give us bright fall colors.
- Left-over fruit is dropped and ready for harvest
- Evergreen trees (ones that don’t drop all their leaves) will stop growing and drop some of their inner needles or leaves
Dormancy in Different Plants
Dormancy won’t look the same across all plants. While a maple catches your eye with its brightly colored leaves, the evergreen nearby might be less showy, albeit just as busy! Even the dormancy period of a plant will change depending on location and that year’s weather patterns.
Take a look at our quick video to learn what to expect when your plants go dormant:
Deciduous trees are the showiest when entering dormancy. The leaves on deciduous trees are meant to be seasonal and typically last for one year. They are usually on the thinner side and aren’t waxy like a holly leaf is. As a deciduous tree enters dormancy, expect its leaves to change color and drop completely, leaving the tree bare.
Evergreen trees get their namesake from the way they keep the majority of their leaves. Their leaves are thicker and more durable than deciduous leaves and might be in a needle form. Evergreens will lose leaves from time to time but never all at once, making them green, year-round. However, don't let the lack of leaf-drop fool you–they still have a period of dormancy–it’s just not as obvious as that of deciduous plants.
Entering and Exiting Dormancy
The timing will vary depending on where you live, the weather patterns that year, and of course, the specific plants you have. For most, expect dormancy to gradually occur for your trees when the temperatures start to drop. In northern climates like Minnesota, this might be as soon as early October. In Southern states like North Carolina, expect to see color change in late to mid November.
The best thing you can do during this transition to dormancy is to be consistent. Don’t stop watering altogether now that your trees are dropping leaves. Instead, water until the ground freezes in your area. While you might need to water less, you’ll still need to support your living plant. Be consistent with your fall care, and it will only help your garden come springtime!
Just like entering dormancy, exiting dormancy won’t happen overnight. When your plants do emerge from dormancy, expect a burst of growth. This might be a flower bud on a redbud tree or some new leaves emerging from your apple tree.
It’s perfectly normal for some trees to be a bit on the lazy side when emerging from dormancy. To help them out, have patience and start watering on a regular schedule. This is also a good time to start fertilizing to support the new flush of growth in spring.
Some areas might experience late frosts or unexpected temperature dips during this time. If you live in one of these areas and notice your plants emerging from dormancy, it might help to protect the fragile, new growth. Do this by using a breathable fabric or frost blanket. And remember, even if some of your plants do get damaged, nature is strong and can often rebound.
And while dormancy largely relates to outdoor plants, indoor plants might experience a lull in growth during the winter months, as well. However, they shouldn’t experience leaf loss. If you’re ever unsure if your plant is dead or just dormant (we know it can be tricky to tell!), just lightly scratch the base of the bark with a coin or your nail to look at the inside. If it’s white and green, your tree is dormant, and if it’s dry and brownish-black, your tree is dead.
If you need further help troubleshooting, reach out to our plant experts for assistance.
Just because plants are entering dormancy doesn’t mean the outdoors have to be dull. Cooler weather brings a multitude of wonderful changes. So, get outside and enjoy the brilliance of nature, the fall colors, and maybe even raking some leaf piles!
Be sure to check out our Regional Fall Planting Tips to prep your plants and set them up for springtime success!