Has anyone lost trees due to warm winters?

[zeejet]

I've been trying to understand whether certain species can actually survive here in coastal areas in Southern California (Zones 10b/11a) and getting a lot of mixed insights. Most seem to think it's fine for deciduous but that they lack fall color and may burn in the summers. Others (like Michael Hagedorn) are adamant that without cold temperatures and large swings in day/night temperatures, deciduous trees will die over the course of a few winters.

The thing is, I've never heard anyone say that they've killed a tree this way and I wanted to see if there are any anecdotes from practitioners in areas where average winter night time lows are 45F or higher (Zone 10b and up). I know that some species tolerate it better than others, but that's getting into the weeds.

Does anyone in Zone 10b or up have experience with this? If so, what varieties?

 

[nuttiest]

I think it could be true, I have a peach tree purchased last year that requires way more chill hours (flat wonderful), and it did not show much vigor this spring or flower. I feel like if things don't flower maybe that is a sign they will decline?

 

[Paradox]

Would you survive if you aren't allowed to get enough sleep or any sleep?

Dormancy is the sleep for a tree.
Species are adapted to grow where they do by their biology, physiology and evolution.
A species that needs a cold winter isn't going to magically adjust to not having a cold winter.

 

[Shibui]

Most seem to think it's fine for deciduous but that they lack fall color and may burn in the summers.

I cannot see why cold winters have any bearing on fall colour.
Fall colour is mostly about cool nights and warm sunny days through that autumn period. There needs to be enough chill to signal the tree to shut down and withdraw chlorophyl from the leaves. Warmer nights slows the process and allows the colours to break down before they are revealed by chlorophyl withdrawal.

Summer burn is caused by trees not being able to transpire enough water to cool the leaves. Maybe an unhealthy tree might transport less water but I don't think summer burn is related to lack of cold in winter.

I certainly grow a number of species that we have been told need winter chill. There must be some threshold for each species and possibly some varieties but that threshold is certainly well above what I've seen some 'authorities' quoting.

 

[hemmy]

Does anyone in Zone 10b or up have experience with this? If so, what varieties?

I was SoCal for 12yrs and 9yrs coastal 10b/11a (in practice or winter lows were only 40-45F). Below is a link on my experience with Japanese Maples (JM) and chill hour requirements. I only got 4 “winters” with the JMs, which some might claim was not enough for an experiment since they will surely die in the 5th. But they had no signs of ill health, other than some tip blight. For most of the 9yrs, I had Chinese Elms from SoCal growers which border on a subtropical species in tolerance. Also Trident maples loved our longer growing season. English oak from seed grew good. I also grew a native tree to zone 8 from OK/TX, the Maclura pomifera, which saw no ill effects from the warmer winters.

Look around your neighborhood and you might be surprised at what deciduous trees are growing.

Post in thread 'Japanese Maples Chill Hour Requirements'
https://www.bonsainut.com/threads/japanese-maples-chill-hour-requirements.43585/post-742599

 

[WNC Bonsai]

The limitation with published chill hour requirements is that most research has been done on commercially valuable species such as apples, peaches, and other fruit.They are constantly looking for apples that can grow in the tropics! Anyway what that means is that most of the info we have on native trees is anecdotal based on what folks will tell you they have seen/experienced. So you take you best shot and learn from it based on what locals tell you they have had work in your area.