Warm Oak

 is an upgrade in the Magic Monkey Knowledge tree. It allows the Heart of Oak upgrade to cost $100 less regardless of game modes. It requires four magic knowledge points invested and Hot Magic.

Prices
The following are prices for the Heart of Oak upgrade with and without the effect of Warm Oak:

Summary
Aside from being a simple discount to Heart of Oak, the main perk with this MK is not from Heart of Oak itself, which would be purchasable pretty cheaply already, is the mere overall discount to Druid of the Jungle and Jungle's Bounty.

Tips

 * Even $100 less can allow for easier accessibility to the Degrow status effect.
 * The mere $100 can make a big difference to affording Jungle's Bounty sooner.

Trivia

 * Warm Oak is the shallowest Druid-only MK in the Magic Tree.