Regrowth Bloons (also known as Regenerating/Regen Bloons, Regrow Bloons) are heart-shaped bloons that grow one extra layer every second, up to their original form (e.g. if a pink regrowth bloon is popped into a green regrowth bloon, it will only regenerate up to pink).
Regrowth Bloons can also have Camo status at the same time, making them particularly dangerous (such bloons are called Camo Regrowth Bloons). Regrowth Bloons can appear on any level of the bloons family line from Red Bloon to Ceramic, although MOAB-Class Bloons can't be Regrowth Bloons, nor their spawned children (With the D.D.T being the only exception in Bloons Monkey City).
Occasionally, the player can send Regrowth MOAB-Class Bloon in Bloons TD Battles. Their MOAB-Class shells will not have any form of regeneration, but once they release Ceramic Bloons, those bloons will become regen and regenerate back to a ceramic. This can also be done with Camo Bloons, allowing players to send a weaker version of the D.D.T at their opponent.
- Main article: Regrowth Bloon/Strategies
- A Regrowth Red is the easiest bloon to pop in the game, as its regrowth does nothing to it if it was a red to begin with and it is larger and therefore easier to hit than a normal Red bloon. These Red Bloons are available in regrowth form in the Sandbox Mode menu, but they are unnecessary because if they are popped, the entire bloon will be gone, so it will not be able to regrow.
- If a tower popped a Regrowth Bloon that had just regrew its old layer, the player will NOT get money for popping that layer. The player will only get money for popping the layer(s) below the ones you popped. Example: a pink regen enters the map, you pop it and make it a yellow, giving you 1 money. If it regens up to a pink, you won't get any money for popping it back to a yellow. You will however, get money for popping the yellow into a green, then blue, etc. This only applies to the Flash version.
- Children of a Regrowth Bloon regrow back to their original parent, regardless of whether the corresponding parent has spawned one or two of them. Meaning for example, a White Regen Bloon can pop into two Pinks, the latter of which can grow back to two whites.
- This sort of regrowth can add extra cash from the split bloons, which is, in this case, called Regen Farming.
- If a Rainbow Regrowth (spawned from a Ceramic) regenerates, it will regenerate straight into an undamaged ceramic shell, requiring another ten hits (more in Freeplay Mode) to pop it back down to a rainbow.
- Corrosive Glue acts faster than regeneration. However, it will take a while before the bloon is totally popped and it will take much longer for corrosive glue to pop regrow bloons than regular Bloons.
- In the Covert Pops Special Mission, bloons that are normally Camo become Regrowth instead.
- Beekeepers are good for popping Regrowth Bloons that do not have multiple children. This is mentioned in the Beekeeper's description, saying "Regrow bloons, beware!"
- Cleansing Foam can remove the regeneration properties of a Regen Bloon and is one of only three towers to be able to do so (the other being the Mortar with a level 3+, 8+, and 13+ Monkey Knowledge Level and a Monkey Sub with a level 4 Specialty Building)
- Regrowth Lead Bloons can be very hard to beat with only Road Spikes and Pineapples because you would have to use a Pineapple to pop the Lead layer. However, by the time you place Road Spikes, the bloons may have regenerated into lead again, and so on.
- Any sort of Spike Factory would remove the threat of Regrow Bloons in general because by the time the Bloons get to the spikes, the bloon will have very little time to regrow once it starts to pop. This is not the case if there are too many Regrow Bloons for the Spike Factory to handle, however.
- Bloon Liquefiers are the best type of corrosive glue against Regrowth Bloons.
- Regrowth Reds can appear in Bloons Monkey City, particularly on MOAB-Class Camo Assault tiles.
- They can be sent on Bloons TD Battles by players.
- Regrowth Bloons can't regenerate while frozen by Ice Towers.
- Technically, they regrow one layer per 25 frames, which actually works out to 1.2 layers a second
- Regrowth Bloons DO NOT regenerate any layer whilst in a Bloonchipper, even if the Bloonchipper has no upgrades.
- In Bloons TD Battles, there was an annoying bug where regrowth bloons with insta regrow right after it was popped, and caused a lot of issues.
- This bug mentioned above might also happen in Bloons Monkey City.
- There used to be a strategy in BTD5 called Regen Farming, where the player could earn ridiculously huge amounts of cash by popping regenerated layers and keeping them from leaking with 4/2 Ninja Monkeys or 4/x Apprentices. However, the Flash Version was updated to where cash cannot be earned from regrown layers, not even from split bloons. However, if the player uses enough Ice Towers to keep a bloon frozen (regens in particular, as this strategy needs x/4 Snipers that can pop frozen bloons) along with Supply Drop Snipers, the regens will stall the round and allow the player to keep Supply Dropping again and again. The new strategy that goes complementary with Regen Farming is called Supply Drop Farming. You can also do that by starting what would be a normal regen farm, and use the supply drops.
- In Bloons TD 5, the player never gets to see a Regrowth Lead Bloon in the main game or Mastery Mode . However, they can see it in Sandbox mode, some Daily Challenges, Bloons TD Battles and Bloons Monkey City.
- In Bloons Monkey City, Regrowth Bloons can appear in assaults.
- In Bloons TD5 Mobile, Regrowth Bloons do change their size which may make them harder to pop than their flash counterparts, due to some Regrowth Bloons being smaller than those in flash.