Mushroom challenges are a feature of Pikmin Bloom, unlocked at level 15. Mushrooms of various colors and sizes appear around the world, and the player can send a group of Pikmin to attack them. Multiple players can join a challenge, and participants will receive fruit and a postcard as a reward, and a score that measures how well they did.
The amount of Pikmin that can be sent on a mushroom challenge by a player will increase over time based on the player's level, starting at 10 Pikmin. The mushroom challenge selection screen lets the player choose which Pikmin to send, and the strength value of the selected Pikmin can be seen in the top left corner. The higher the strength, the faster the Pikmin will be at completing the challenge.
Only three mushroom challenges can be done by a player in a day. Up to five people are able to join in on a single mushroom challenge.
Mushrooms grow at points of interest in the real world, similar to Big Flowers. They can only be seen and interacted with when they are less than 600 meters away from the player. After the mushroom is destroyed, it grows back in the same location 15 minutes later, without any input. The mushroom type that grows is randomized, but there seems to be a system where some mushrooms are removed from the selection if no players nearby have access to the corresponding Pikmin type.
Mushrooms come in various forms that differ in size and color. The hierarchy of the sizes are small, normal, large, and giant, with each size increasing in health. The larger the mushroom, the bigger the reward for destroying it. There are 8 colors of mushrooms for each size, except for giant mushrooms which only come in red. Some mushrooms have more or less health than other colors of the same size, such as gray or white mushrooms, being tied to the matching Pikmin's attack power. The color of mushrooms can also determine the type of nectar players get as a reward.
When a mushroom is selected, either from the map screen or expedition list, the camera will focus on the mushroom, with a photograph of its corresponding real-world landmark behind it. The screen displays some basic information about mushroom challenges, as well as 5 circles that can be filled with icons of the Miis of the players who have joined the challenge. There is a Join button which progresses to the selection screen.
In the selection screen, the player can choose which Pikmin to send. A list of all the player's Pikmin appears, and by tapping one, it can be added to or removed from the mushroom attacking group. The maximum size of the group depends on the player's level. Pikmin with an advantage against that mushroom type (see the next section) may jump in the list when selected for the challenge. Selected Pikmin also appear in front of the mushroom in the camera view. There is a GO button in the lower right corner; tapping it sends all the selected Pikmin to attack the mushroom.
Once the Pikmin are sent on the mushroom challenge, they rush towards the mushrooms and start attacking them. Most Pikmin types latch on to a mushroom and start attacking it at a constant rate, with each attack doing some damage. Rock Pikmin instead jump towards a mushroom from a distance and roll back to jump again. From time to time, Pikmin get off the mushroom, walk back to their starting position, and walk back to the mushroom to start attacking again. Each hit decreases the health of the mushrooms, though not by a set amount; see the Time section for more details. From time to time, one of the mushrooms in the group will collapse, leaving the Pikmin attacking it to start attacking another one. The intervals at which mushrooms break depend on the number of the mushrooms in the cluster: 4 for small, 7 for normal, and 10 for large, such that mushrooms break at regular intervals. For example, in a large mushroom group, one of the mushrooms will break for each tenth of health depleted.
When the health is fully depleted, the mushroom challenge is cleared. The player is provided with their score, the time it took to destroy the mushrooms, and a star rating, followed by the Pikmin bringing a postcard about their challenge and a small number of shiny fruits to be given to the player, providing them with nectar of an uncommon type. Each Pikmin that was sent on the mushroom challenge also gains some friendship (though this actually happens at the start of the challenge, not the end).
When the player is selecting Pikmin for the mushroom challenge, a power value appears in the top left corner of the screen. This shows how strong the selected squad is against that mushroom. (Note that the value displayed is rounded from the actual value.) Adding a Pikmin will increase the value by some amount. The amount depends on 5 variables: the type of Pikmin, its friendship, its maturity, whether it is a Decor Pikmin, and the color of the mushroom being attacked. The equation below is the overall equation for calculating the power contributed by a single Pikmin; the paragraphs below explain what each variable means.
Each Pikmin type has a base attack power. Red Pikmin, Yellow Pikmin, and Blue Pikmin all have the standard base attack power. White Pikmin and Winged Pikmin are slightly weaker, while Purple Pikmin and Rock Pikmin are slightly stronger. The exact values used are in the table below.
A Pikmin's maturity contributes to how strong it is. Leaf Pikmin have the standard attack power, and each maturity level above that increases the power slightly. Rare flowers, such as pansies and roses, are stronger than regular flowers. Bare Pikmin, obtained by feeding them too much nectar, are slightly weaker. The exact values used are in the table below.
A Pikmin's friendship contributes to how strong it is. For the purposes of the formula, the value used is the number of completed hearts. The fractions of a heart between full hearts doesn't matter, so a Pikmin with 1.1 hearts of friendship and a Pikmin with 1.8 hearts of friendship have the same attack power of 1. The number of full hearts ranges from 0 to 4, so a value in this range is used in the formula.
If a Pikmin is a Decor Pikmin, 4 points will be added to its attack power. This variable in the equation can be either 0 (for non-Decor Pikmin) or 4 (for Decor Pikmin).
The final variable is the type of mushroom, and this is the last step in calculating attack power. If a Pikmin is the same color as the mushroom, its attack power will be multiplied by 2. In other cases, certain Pikmin types may have an advantage or disadvantage against certain mushroom types. The multipliers for each Pikmin-mushroom combination are in the table below.
As an example, picture a standard Purple Pikmin with 2.5 hearts of friendship and a bud on its head, against a red mushroom. This gives it a base damage of 5.2, a maturity multiplier of 1.1, a friendship value of 2, a Decor bonus of 0, and a mushroom multiplier of 1.1. Putting these values in the formula gives (5.2 × 1.1 × (1 + 2/10) + 0) × 1.1, or 7.5504. The game would round this up to 8 for displaying to the player.
The amount of time it takes to complete a mushroom challenge (in seconds) is calculated by taking the health of the mushrooms, dividing it by the total attack power of the Pikmin on the mushroom challenge, and multiplying it by 4. For example, a normal-size mushroom with 21,000 health, attacked by a group of Pikmin with 200 attack power, should take 420 seconds or 7 minutes to destroy. Although the game presents damage as something dealt by each individual attack, each Pikmin hit actually does as much damage as it needs to decrease the health of the mushrooms at a linear rate such that they are fully destroyed at the calculated time.
At the end of a mushroom challenge, the game gives the player a score and a star rating. Star ratings are presented as ranging from 1 to 3, but they actually range from 1 to 4. The score obtained on a mushroom challenge is dependent on the attack power of the Pikmin group and the size of the mushroom, and the star rating is dependent on the score.
While the exact system for calculating scores is not understood, it is clear that it's based around thresholds for each star rating. For small mushrooms, the minimum scores for each star rating are multiples of 720 – 1440 for 2 stars, 2160 for 3 stars, and 2880 for 4 stars (the maximum score). These thresholds are doubled for normal-sized mushrooms, doubled again for large mushrooms, and doubled again for giant mushrooms. Score is calculated according to the time taken to defeat a mushroom, relative to its size and colour. This is especially apparent when multiple players join at differing times, as the delay will result in a decline in score, compared to a scenario where the same players join in unison. Because time requirements are scaled based on mushroom HP, attack requirements for a certain score are the same across all mushroom colours, so long as the size is the same. However, this scaling does not factor the matching Pikmin colour's base attack. As an example, higher scores can be achieved on purple and grey mushrooms with less Pikmin, as Rock and Purple Pikmin naturally possess the highest base attack of all Pikmin species.
The following table shows the approximate minimum total attack power for each star rating and mushroom size, based on experimental data. Note that results when teaming up for mushroom battles may vary due to differences in joining times. Values marked with * are approximated with rough calculation.
Once a mushroom challenge is complete, a postcard and some fruits will appear, and the Pikmin on the mushroom challenge will collect them. If too few Pikmin were sent on the mushroom challenge to carry all the rewards, only some rewards will be collected; the postcard has the highest priority. The fruit rewards depend on the star rating for the challenge.
This table shows the nectar type for each mushroom type as it is currently. When multiple types can come from one mushroom, each fruit given by a mushroom challenge can have a different nectar type. The distribution has changed over time, and past distributions can be seen in the History section.
This table shows the number and type of fruits given by a mushroom challenge depending on its star rating; see the Fruit (Pikmin Bloom) article for details on fruit sizes.
If a Huge Seedling is given, its location type will be based on the mushroom's location.
When you first unlock mushroom challenges, you likely won't be able to get very high scores because of the limit on how many Pikmin you can send to a challenge. At this stage, focus on attacking larger mushrooms as they give more rewards for low star ratings, and send Pikmin you want to increase the friendship of, since challenges give a small amount of friendship to participating Pikmin.
After gaining a few levels and increasing your maximum challenge group size, you'll start being able to get higher scores. To optimally prepare a squad for challenges, select Pikmin that are the same color as the mushroom you'll be attacking, and Pikmin with higher friendship values (preferably Decor Pikmin). Feed them all a rare type of nectar (the types you get from completing challenges), and send them on the challenge. With a high enough level and enough Decor Pikmin, you should eventually be able to reach 4-star scores on small mushrooms.
Getting 4-star ratings on larger mushrooms requires multiple players, so if you have friends who play Pikmin Bloom, consider working together to complete a challenge as quickly as possible.
The following changes have been made to mushroom challenges over time: