ACNH Flower Genetics Guide

By Paleh

Update: Thanks to data mining from Aeter (Aeter#9823 on Discord), we now know the genes of all the New Horizon flower species! Huge thanks for getting this info! This guide has been updated with all the new gene data for all species.

Animal Crossing New Horizons uses a surprisingly complex genetics system. Every flower has its own unique genes it carries, and you cannot always tell what recessive genes a flower carries based solely on its color. The system uses basic Mendelian genetics, the same system that’s normally taught in school. Since it’s Mendelian genetics, you can also make use of punnett squares to predict offspring.

The gene system is able to record up to 4 different genes for each flower, however most species only use 3, with only roses using all 4.

Flowers from seed bags always have the same genes, so these are vital for being able to predict what offspring you’ll get.

Native flowers found on your cliffs at the start of the game have seed genes, however, since there’s a risk of them breeding before the player reaches them, you should be wary of using them for your breeding if you can’t guarantee the flower isn’t offspring of another.

Hybrids found on mystery islands have different genes than those you would normally get by breeding the seed bag parents. Often these flowers have the genes necessary to produce third/fourth generation hybrids (e.g. blue roses, purple windflowers, etc.). Base color flowers (red, yellow, and white) found on mystery islands have the same genes as seed bags and can safely be used for breeding.

Animal Crossing New Leaf uses an almost identical genetics system as New Horizons. The ACNL version of this guide can be found here.

The genes

Disclaimer: The genes are not labeled in the game’s programming, they’re simply represented by numbers in-game. The labeling here is simply to make it easier to read and understand for players. The game itself only uses binary and 0-2 numbers in the source code. All names and definitions are a matter of interpretation, check the technical explanation section for details on exact implementation.

While four genes exist, only roses use all four. This section will talk about the gene’s general purpose mainly as it applies to roses, but the genes have similar or identical purposes on other species.

The actual displayed color of the flower is based on genes, but when you get to later generations with all of the genes interacting, it’s not always easy to predict which genes will cause which color due to complex gene dominance rules.

If you’re curious what color each gene combination is associated with, there’s a spreadsheet below with the gene values and colors. This can be helpful to look through if you’re trying to make complex breeding plans.

Gene spreadsheet

Despite the unpredictability of some gene combinations, there does seem to be a pattern on what each gene does to a flower.

Rr gene

Controls whether a flower is red based or not. Red based flowers are red, black, pink, and orange. Non-red are yellow, white, and purple.

Note: Not all flowers with the R gene will be red-based, since other genes can cover it, but a flower with the genes rr will never be red-based.

RR or Rr = red-based flower

rr = non-red flower

Yy gene

Controls whether a flower has any yellow in it (yellow or orange). Other genes can sometimes cover this gene up though.

The same note for the Rr gene applies here.

YY or Yy = yellow or orange

yy = non-yellow

Ww gene

Controls whether a white flower will be white or show its underlying color: either purple or blue depending on the species.

White flowers are fairly recessive to most colors, so this gene will only have an effect if the white isn’t getting covered by reds, yellows, or other colors.

WW or Ww = white

ww = purple or blue

Technical note: For the W gene only, WW is associated with 00 instead of 11. See the technical explanation section for more info.

Ss gene

Controls which shade the red-based flower will be. Pink is the lightest shade, red is the middle, and black is the darkest. This gene has no effect on non-red flowers.

Note that in species without the S gene, pink is instead obtained by certain interactions between the R and W gene.

SS = pink (sometimes red in some species)

Ss = red

ss = black (or orange when combined with yellow)

Technical explanation

This section is not required to understand the genetics system. It’s meant for those wanting to understand what the game is actually doing behind the scenes. You can skip to the next section if you’re just interested in breeding your flowers.

Every flower has their genes stored in the item’s flag value. The genotype portion of the flag is an 8-bit number. Genes are represented by 2-bit pairs within this flag, and alleles are represented by a single bit within the gene pair. For example, a red rose from a seed bag has the flag value of 11-00-00-01.

For species with fewer than 4 genes, the higher bits are simply always set to 0, with only the lower gene pairs used.

When bred, each parent passes on one random allele from each gene, and they’re combined together to make the offspring’s genes.

For example, if you breed two 11-00-00-01 red roses together, the offspring can be any of the following:

11-00-00-00

11-00-00-01

11-00-00-11

If a flower has a “1 allele” and a “0 allele” on a gene, that gene’s value in the flag is always stored as 01, never 10.

It is also possible for flowers to asexually reproduce under certain conditions, instead of crossbreeding with another flower. This produces offspring with the same genes as the parent, essentially just duplicating/cloning the flower.

Certain areas of the games code also process genes with an alternate “trinary”/numeric format instead of binary, with the following conversion (including genetic notation):

Binary

Trinary

Genetic

00

0

rr

01

1

Rr

11

2

RR

This trinary format can be handy for writing out a flower’s genes in a shorthand way. For example, instead of writing out a seed red rose’s genes as 11-00-00-01 or RR-yy-WW-Ss, you can instead just write 2001 to represent the genes.

Important note: Most genes have been labeled where 11 is dominant, however I’ve labeled the W gene opposite, where WW = 00, because the color caused by 11 (purple and blue) behaves similarly to a recessive color. Recessive genes are normally labeled with a lowercase gene name by convention, so I’ve decided to stick with gene naming conventions here. Some guides/tools do not flip this gene, and leave WW = 11, so keep that in mind when looking at other guides and tools.

The genotype flag’s 8 bits are stored alongside other data within a larger flag (currently unconfirmed which of the 3 flags it’s stored in) for an item. The gene order is reversed, so roses are [gene 4]-[gene 3]-[gene 2]-[gene 1], and other species are 00-[gene 3]-[gene 2]-[gene 1].

Flower species

Roses

Roses are the only species to make use of all 4 genes: R, Y, W, and S.

Note: There is only a single gene combo that will display as blue. All other colors could have different underlying gene combinations, but blue’s is always the same. This also means that when you breed two blues together, they will only ever produce more blues.

Seed red = RR-yy-WW-Ss

Seed yellow = rr-YY-WW-ss

Seed white = rr-yy-Ww-ss

Red + yellow: orange = Rr-Yy-WW-ss (50% chance)

Red + red: black = RR-yy-WW-ss (25%)

Red + red: pink = RR-yy-WW-SS (25%)

Red + white: pink = Rr-yy-**-Ss (50%, W gene can be anything)

White + white: purple = rr-yy-ww-ss (25%)

Black + yellow: orange = Rr-Yy-WW-ss (100%)

Orange + purple: “hybrid red” = Rr-Yy-Ww-ss (25%, note: another 25% of the red offspring will not be hybrid reds)

Hybrid red + hybrid red: blue = RR-YY-ww-ss (1.6% / 1 in 64)

Mystery island orange = RR-YY-Ww-Ss

Mystery island pink = RR-yy-ww-SS

Island orange + island orange: blue = RR-YY-ww-ss (6.25%)

Island orange + island orange: special red = RR-YY-ww-Ss (12.5%)

Special red + special red: blue = RR-YY-ww-ss (25%)

Blue rose method

This genetics system explains why blue roses are notoriously difficult to get. Blue roses only ever have the genes RR-YY-ww-ss, never anything else. This means they need genes from red, yellow, and white, hence why crossing purple and orange sometimes works. However, only half of the reds produced will have the required Rr-Yy-Ww-ss genes. The other half will be Rr-yy-Ww-ss, which are incapable of producing blues, and there’s no efficient way to test which is which. Furthermore, even with good reds, only 1 in 64 of the offspring will be blue.

The quickest and most surefire way of getting blue roses in New Horizons is by using Mystery Island oranges, however you can only find these if roses are your native or sister flower (i.e. the ones that spawn on your cliffs, or the ones Tom Nook gives you seeds for), so for many users it’s impossible to obtain these.

There are two alternate paths: one will guarantee you hybrid reds that are capable of making blues (at a very low rate), and the other will gradually increase your chances up to 25% of blue offspring per pairing, to be certain you’ll get blues by the end. The path to increase your chances involves more generations, and test breeding the offspring at one step, but it’s absolutely guaranteed you will get blue roses by the end of this method every time.

It’s currently unclear if the method of increasing chances is faster than simply breeding a lot of hybrid reds and crossing them all with each other, but it is more fool-proof.

Guaranteed blue rose path (v2)

If you’ve already started v1 of this path, you can find the original instructions here. If you haven’t started yet, it’s recommended to use v2 instead.

Note: It’s recomme