Attacks convert Regrow Bloons into normal Bloons.
~ In-game description

Heart of Oak is the second upgrade in the middle path for the Druid in BTD6. Heart of Oak allows all Druid attacks to strip Regrowth Bloons of their regrow property. Interestingly, because the "degrow" effect is applied on hit rather than on damage, Heart of Oak can remove regrow from Regrow Leads even if it cannot damage them.

It costs $295 on Easy, $350 on Medium, $380 on Hard and $420 on Impoppable.


  • A Monkey Knowledge upgrade named Warm Oak reduces the price of this upgrade by $100. Note that this applies after difficulty price multipliers.
    • The same Monkey Knowledge can be used to make it easier to farm with Jungle's Bounty Druids.
  • As a crosspath, this upgrade is largely ignored because the Druid's removal of the Regrow property tends to not be very impactful.
  • Heart of Oak thorns can remove regrow from Regrow Leads even if the thorns themselves cannot pop them. This may be useful in specific challenges.

Version History (BTD6)Edit


Buff Heart of Oak now allows all attacks to degrow Regrow Bloons, not just thorns.



  • Heart of Oak, similar to Counter-Espionage and Perishing Potions, removes one specific bloon property type from bloons.
    • Coincidentally, all of these upgrades come from Magic Monkeys as the 2nd upgrade of their 2nd path (Druid, Ninja, Alchemist, in the respective order).
  • Version 18.0 added a secret undocumented buff that allows all attacks including thorns to degrow Regrow Bloons. The description was changed from "Thorns convert Regrow Bloons into normal Bloons." to the current description to accomodate these changes.
    • This change has also made the 2TC combo Superstorm + Sky Shredder possible, which allows Round 61 to be possible with just a 3-2-0 Druid. This was shown on the official r/btd6 subreddit. Link.
    • This buff was not at all mentioned in the Version 18.0 patch notes. It was, however, officially mentioned in the Version 19.0 patch notes.
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