Pruning Decision Trees

Question

Below is a snippet of the decision tree as it is pretty huge.

How to make the tree stop growing when the lowest value in a node is under 5. H

Answer 1

Edit : This is not correct as @SBylemans and @Viktor point out in the comments. I'm not deleting the answer since someone else may also think this is the solution.

Set min_samples_leaf to 5.

min_samples_leaf :

The minimum number of samples required to be at a leaf node:

Update : I think it cannot be done with min_impurity_decrease. Think of the following scenario :

      11/9
   /         \
  6/4       5/5
 /   \     /   \
6/0  0/4  2/2  3/3

According to your rule, you do not want to split node 6/4 since 4 is less than 5 but you want to split 5/5 node. However, splitting 6/4 node has 0.48 information gain and splitting 5/5 has 0 information gain.