Step 1. Die
Step 2. Get someone to mourn you. You will get a drink ticket.
Step 3. Go to Naraka.
Step 4. Keep going till you get to hells bar.
Step 5. Exchange your ticket for a "Wine of the dead".
Step 6. Pour the wine on your cultavations.
You can also buy wine from auction. Hope I helped.
Also all resources have a lifespan so you could just use it up.
If you want to remove a Patch you will have to kill the tree too. You can kill them by not watering or petting but, even if you find a way to stop others doing that it will still take a very, very long time - with the exception of wood trees which you can kill quickly by over chopping. So for most trees you normally have to poison them.