Happy Little Trees comes with an additional plugin that is called Treescale.esm.
This plugin scales Treepineforest01, 02, 04, 05 and Treepineforest 01, 02, 04, 05 to a size of 120 percent.
But you can set your own preferred tree size via SSEEDIT.
And this guide shows you how to do it.
First grab SSEEDIT and install it into a directory that you want. The tool detects the installation and loads the files automatically.
Then you open up the tool and deselect any other plugin besides the Treescale.esm. 
The tool will load the plugin and all dependend plugins.
Then select Treesize.esm and open the context menu via right click.
Select Apply Script.
Select the script "Scale Tree References" from the dropdown menu.
Type in your prefered size multiplier.
Click ok and close the application.
SSEEDIT will save the plugin during its shutdown. And you can choose if you want to create a backup of the esm.
That's it.
You have your personal tree size and all you have to do is to recreate your tree lod.
15 comments
You say that the current % of scaling for trees are actually at 120%, but how does it work with the 0.6 value? What is the formula exactly? 0.6 is default value? I'm a bit confused.
Thanks a lot for your work, it's my favourite trees now.
Concerning the cumulative way the script work, it seems to be an important thing to point out. Thanks again.
Two years later I'm figuring out how to use SSEdit. Thanks so much for your work in testing and figuring out how scaling trees works for this mod.
Is there any solution for scale snow trees? By this article, treescale.esm does scaling only pinetrees.
Thank you for created this mod. I always use this.
Would this affect only the happy little trees that aren't being overwritten, or would it affect the trees from other mods that are overwriting the happy little trees mod?
And if that's the case, can you specify which tree type you want changed?
I was soo happy when I got this working.
Because it was very tricky.