I've taken a look at the code and genetics for the flowers in Animal Crossing New Horizons and thought I'd share a simple explanation since most flower breeding guides online just say colour 1 + colour 2 = colour 3 and I'm sure some of you aren't getting the colour you'd expect
The flowers aren't just labelled in the code as red or yellow; they have genes that influence their colour. Two flowers of the same type and colour could have different alleles (versions of each gene)
Even if you're sure of the genes in a specific pair of flowers, you might be left with a CHANCE of getting the colour you want. First a little explanation of what genes there are. There are 4 genes in the game but only roses use all 4. The rest only use 3 (not always the same 3)
In case you're not familiar with genetics we'll just look at one gene to begin with. The pansies have a gene most people call R or r because it plays a role in making red (and similar) flowers. Each pansy has two R/r genes because there's one from each parent
The gene can come in two forms (we call them alleles), either an R or an r. This means a pansy either has RR, Rr, or rr depending on what the parents gave it. Pansies also have yellow and white-related genes so they could be RR-yy-WW or rr-yy-Ww for example. Two of each gene
There are rules in the code for what the genes do and they can influence each other in complex ways. But generally the red, yellow, and white genes work like this:
RR or Rr = red or similar
rr = not red at all
YY or Yy = yellowish
yy = not yellow at all
I'll come back to white
RR or Rr = red or similar
rr = not red at all
YY or Yy = yellowish
yy = not yellow at all
I'll come back to white
You can imagine a flower that's rr but YY as more likely to be yellow than red, but it might depend on what the other genes are doing and that's an important point. Your flower could be RR/Rr and YY/Yy so is it red or yellow? Sometimes one overrides the other
Before going to a real example I'll quickly mention the other two genes. The white gene works a little differently in that it's technically a purple or blue gene but it's recessive so if we called it P/p then PP and Pp would actually give white. It takes pp for purple or blue
So to keep things simple it makes more sense to ignore how it's labelled in the code and refer to it as a white gene where WW or Ww give white and ww gives purple or blue
The final gene I'll call X or x and it's responsible for the shade of the flower when it's red or similar (it does nothing in flowers that are yellow, or blue etc).
XX = usually pink (sometimes red)
Xx = red
xx = black (sometimes orange)
XX = usually pink (sometimes red)
Xx = red
xx = black (sometimes orange)
The important thing to understand at this point is that you could see three pink lilies and one could be RR-YY-Ss, one could be RR-yy-SS, and the other could be Rr-yy-Ss. If you're planning on using pink lilies for your breeding it matters which you use!
The good news is that there are some rules that don't change: when you buy flowers as packets of seeds they always have the same alleles. If you buy red lilies they WILL be RR-yy-Ss so at least you know something for certain
The standard colours (red, yellow, white) found on mystery islands also have those same alleles as the seed packets. However, the hybrid colours on mystery islands (blues, oranges etc) WILL have different alleles and that makes them useful for breeding!
I'm using a lot of purple flowers on my island and I'd love purple pansies but I'm struggling to get them so I thought I could use it as an example to show how weird it can be and why it's proving difficult compared to others I've bred or found
Most guides say you need two hybrid reds or two hybrid oranges (i.e. not reds you bought but reds you've bread from red+blue) to make purple but it's a lot more complicated than that. There are 3 ways to get purple pansies and 2 involve mystery island flowers
Let's assume you don't use mystery island flowers. The only purple pansy you can make is RR-yy-ww. To get that you breed two reds. A simple guide would say they can't be any two reds but hybrids, but what's more important is they need to have specific alleles
Here are the alleles for pansy seeds bought from the shop:
Red = RR-yy-WW
Yellow = rr-YY-WW
White = rr-yy-Ww
Purple needs two "hybrid reds" which is just a red that's quite different than the shop red:
Hybrid red = Rr-yy-Ww
So first we gotta make some of them
Red = RR-yy-WW
Yellow = rr-YY-WW
White = rr-yy-Ww
Purple needs two "hybrid reds" which is just a red that's quite different than the shop red:
Hybrid red = Rr-yy-Ww
So first we gotta make some of them
Hybrid reds need an ordinary shop-bought red and a blue and the good news is they will make hybrid reds 100% of the time (I'll show you that in a bit). The red's no problem but the blue can't be bought so we need to combine two whites to make a blue first
Here's where we start to see where chance comes into this. Remember whites are rr-yy-Ww? Let's put that in a good old Mendelian punnet square to see what we get. We put the alleles from the standard shop-bought whites onto the sides of the square representing both parents 
The coloured squares represent all the different combinations we could get from two store-bought white pansies breeding. There are three different variants we could get. If you count them you'll see that they're not equal. Half of the time we'll get rr-yy-wW: another white!
25% of the time we'll get rr-yy-WW and that's also white! So 75% of the time we just get more whites but with potentially different alleles. The final 25% is the rr-yy-ww, which is the blue we've been trying to make!
So far we've bought reds, bought whites, bred whites for a 25% chance of getting a blue, and now we just need to breed the blue with one of the reds to get our hybrid reds we'll need. This part is very simple because there's a 100% chance the offspring will be the hybrid red
See it's all one colour? A blue and a store-bought red can only ever give you the hybrid red we're after, which is helpful! Unfortunately the very last part isn't at all. To get our purple all we have to do is breed two hybrid reds together but let's see why it's frustrating
It turns out two hybrid reds with Rr-yy-Ww can create all sorts of combinations of alleles. Many of these will just be more reds with all sorts of combinations of alleles that will make them difficult to use in breeding. Here's the breakdown. Look for RR-yy-ww to find our purple
That's right. If we do everything perfectly, buy reds and whites, breed whites for a 25% chance of getting a blue, breed the blue with reds for 100% chance of hybrid reds and then breed those... we only have a 6.3% chance of getting the purple
So if you're struggling to get purples you might just need to be patient as the odds are against you. Or the worst case scenario is the previous breeding was done incorrectly and you don't have the hybrid reds you thought you had
Quick stop here to note a couple of things. Firstly I'm using this website to make the punnet squares: scienceprimer.com/punnett-square…
Secondly, in one tweet I mentioned an S gene and that's the X gene I was referring to earlier. The source I used for the combinations uses S. I prefer X
Secondly, in one tweet I mentioned an S gene and that's the X gene I was referring to earlier. The source I used for the combinations uses S. I prefer X
You can see the different combinations here: docs.google.com/spreadsheets/d…
This is why the mystery islands are so amazing for breeding! 6.3% chance of a purple after all that other breeding isn't great but there are two other ways to make purple pansies using mystery island flowers
Well there are two other combinations of alleles that can get you purple but there are three different ways you get purple from mystery island pansies. The first is another way to get the same RR-yy-ww we were trying to get earlier: breed two mystery island blue pansies
Mystery island blue pansies are Rr-yy-ww so there are three different combinations you can get. There's a 25% chance you'll get the glorious RR-yy-ww we were working so hard to create earlier!
Now we've covered all the ways you get the RR-yy-ww purple but there are another couple of combinations that also give purple: RR-YY-ww and RR-Yy-ww. The first we get from breeding two mystery island orange pansies (RR-YY-Ww) again for a 25% chance of purple:
Last but not least, with another 25% chance of giving you a purple... we can breed the mystery island orange and mystery island blue pansies together for another unique combination of alleles that make the final purple variant (RR-Yy-ww)
So hopefully you can see now why someone saying colour 1 + colour 2 = colour 3. For purple pansies there's a lot going on. It's simpler if you stick with mystery island hybrids but there's still only a chance that you'll the purple you're after
If you're interested in breeding a specific colour of a specific flower let me know and I'll tell you the most efficient way to do it :) I hope this was at least interesting
Also it’s called a Punnett square. My autocorrect kept making it Punnet
I didn't know this about visitors watering flowers, thanks for sharing!
I wouldn't change the flower breeding system at all because it makes it feel more realistic and keeps you from getting all the flowers in your first couple of days but if I could change something...
People were asking how to get blue roses which are very tricky to breed! Roses are the only flower to make use of all 4 genes (the rest use 3 but not necessarily the same 3) and only one combination of alleles makes a blue rose. I made a guide:
