A lot of important tree care happens during dormancy. For instance, winter tree pruning and fertilizing can be done during dormancy. Trees follow an annual growth cycle. Dormancy is the period in this cycle when a tree is not actively growing, i.e. late-autumn to mid-winter. Therefore, it is worth knowing when a tree is actively growing and when it is ‘asleep’. Moreover, if you go through long winters like here in Western NY, you might want to know: ‘when do leaves start to grow back on trees’?!
Why Do Leaves Grow Back in the Spring?
Firstly, let’s consider why leaves start growing in the spring. This may seem obvious. However, the answer to when do leaves start to grow back on trees, has a lot to do with how trees ‘know’ when to grow. That’s because a tree’s processes to go dormant in winter go hand-in-hand with its processes to start growing in spring.
Step 1: Going Dormant
The process begins in the fall. As days shorten and temperatures drop, trees prepare for dormancy. At the same time, a tree prepares to leaf out in the spring. First, as the nights lengthen in autumn trees stop growing longer twigs. Instead, they create resting buds. Likewise, chlorophyll production slows and leaves lose their color. Eventually, a layer of cork at the base of the leaf cuts it off from the tree and it drops.
While trees may appear dormant at this point, they are actually in a state of pre-dormancy. During this time a tree can be pushed back into growth. This is key to knowing when to fertilize trees. In other words, fertilizing too early could encourage fragile growth just as winter sets in! Therefore, know that true dormancy begins several weeks after growth stops.
Step 2: Staying Dormant in Winter
Okay, so now we know how a tree prepares for dormancy. But how does it stay dormant through winter. Similarly, how does it ‘know’ when to start growing leaves again? Well, first it needs to go through a certain number of ‘chill hours’. Chill hours are those spent between 44F and 30F. While we don’t yet fully understand how trees ‘count’ their chill hours, typically it appears northeastern hardwoods have had enough by January to enter post-dormancy.
To human eyes, this can look the same as dormancy. After all, you don’t see a lot of leaves out in January! However, at this time winter’s cold stops growth and a tree’s freeze-resistance is highest during post-dormancy.
Step 3: Leafing Out in Spring
Finally, we’ve arrived at discussing when do leaves start to grow back on trees. This happens in the spring as trees are warmed to the right temperature. At this point, the hardened bud the tree created just before dormancy bursts open and new leaves emerge.
In other words, autumn nights and chill ‘tell’ a tree to prepare for winter. Then, a tree accumulates its ‘chill hours’ during mid-winter. Next, the deep freeze of winter stops new growth. Finally, the longer days and warmer sun of spring ‘tell’ the tree to leaf out.
When Do Leaves Start to Grow Back on Trees in New York State
The question of when exactly do leaves start to grow back on trees in New York State will vary year to year. For example, in response to why leaves come at different times in Canada, the University of Toronto explains:
In 2010 the buds may have burst two weeks earlier than this year because the autumn of 2009 was cold enough for the trees. So, once the night length got longer, the trees went into their dormant program, and then the tree was able to fulfill its cold days requirement and then there were enough warm days to allow the tree to say, “OK, timing is right, I can burst bud again.”What Makes Leaves Sprout in the Spring
Thus, when the leaves come back depends on the conditions of the previous fall. It also depends on the local conditions. In particular, in the northeast our trees tend to leaf-out later than in other regions. Due to the risk of a sudden freeze – need we remind you of the Rochester Ice Storm of ’91 – trees in Western NY leaf out in late April and early May.
Spring Tree Service in Webster NY
Worried that your trees aren’t leafing out as expected? Stay calm! Different trees leaf out at different rates. However, if you do notice trees in distress you might want to contact an arborist in Webster? Or, let Arbor Tree Experts know! Established in Webster in 1985 we are a fully licensed and insured tree service in Webster. We offer tree removal, tree pruning as well as stump grinding. Likewise, we can help you choose the best trees for your unique landscape. Contact us for a quote.