I couldn't find a setting to change the growth speed of trees, so I decided to try to make a mod of my own for use with Ago's mod loader. It lets you change the chance that a tree will age one step when its tile is polled, and also to modify the odds that a shriveled tree will die when polled.
The mod has been tested manually by me, and seems to work as intended. It has however not been tested for any longer periods of time, and it is also the first mod I have ever done, so please be careful before you decide to use it on any established server!
I hope the mod can be of use to you, and I welcome any advice or comments you have that may help me further improve it. Mod info can be found below:
Make sure you have Ago's mod loader
Download the mods.zip file here: https://github.com/Hepfem/WurmTreeGrowthMod/releases
Extract the zip and put the files inside the mods folder in your WurmServerLauncher directory
Edit the settings in wurmtreegrowthmod.properties to your liking
The mod has three settings:
The first is activateMod. Use it to activate or deactivate the mod.
# true: Activate mod
# false: Deactivate mod
The second is treeAgingChanceMultiplier. Use it to increase or decrease the chance of a tree advancing to the next age stage when its tile is polled.
# Multiply chance for tree to age upon polling.
# Value = 1.0: No change
# Value = 0: Trees will never age
# Value >= 225: Trees till always age
# Value < 1.0: Decrease the rate at which trees ages
# Value > 1.0: Increase the rate at which trees ages
The third is treeDeathOdds. Use it to increase or decrease the chance of a shriveled tree dying (replanting itself). A higher value means a smaller chance of death, the formula is: chance of death = 1/treeDeathOdds. The exception is a treeDeathOdds value of zero, which will result in a zero chance of death.
#Set odds (0-127) of a shriveled tree dying upon polling.
# Value = 15: No change (1 in 15 chance that tree will die)
# Value = 0: Shriveled trees never die
# Value = 1: Shriveled trees always die
It is recommended that both treeAgingChanceMultiplier and treeDeathOdds are modified together. Otherwise you may end up with a forest with unbalanced tree ages. If you for example make trees age faster without also making them more likely to die, you will eventually end up with a forest that has a higher ratio of shriveled trees.
Remember that a faster tree growth will automatically result in faster tree spreading, since the check for tree spreading occurs when tree age advances. Odds for tree spread can be changed in the original server settings.