https://mods.factorio.com/mod/settingsforbobsgreenhouse
These settings are specifically for this mod. These settings will allow you to change the time it takes to grow, and the power usage required by the same amount you change growth time.

I myself, play with it set to 6, which multiplies the time taken to grow wood by 6 times, and divides the amount of power required by 6 times. I don't play marathon mode, so it was giving me way too much wood too fast so I reduced its speed to be a more realistic number. You can use this with Marathon too if you want, and you can increase the grow speed by going less than 1, e.g. 0.5 will be 50% faster.