In a lot of plants, a virus (sometimes carefully planned by breeders) causes the streaking. Sometimes it's a hybrid of 2 parent plants. It could also be environmental. Think of all the variations in human skin...same thing with plants.

That looks like a variety of portulaca in the Margarita line....coincidentally called 'Peppermint '.

It's beautiful.

nothing 'caused' it..

it was bred into the seed you sowed ...

as noted.. its a named variety ..

many such plants end up sterile ... or if they do self sow.. you may or may not get the streaking in the second generation ... and eventually.. it will break down into the attendant solid colors .. i say the generations are degrading back toward the species.. but i dont know if that is fancy science words.. or just my way of thinking abut it ...

ken

ps: if you are asking how they did it.. its all magic.. no real understandable answer.. lol...

I checked into it before the post, seeing there is a hybrid called peppermint.

But this was not bought as a peppermint, it was a multi-color that bloomed normally until now. It doesn't appear to be from seeds of the original as the number of plants is not different too. There is an orange one near it that is part red stripes, I didn't know if stripes were a naturally occurring variation.

I have had plants come back as a different color before. I do not know how, but it is pretty. :)

You planted a tray of bought solid color Portulaca but that doesn't mean that a couple of seeds of the peppermint variety didn't get mixed in with the solid colored ones when they were planted at the nursery. I have often had this happen with seeds and plants.

For instance I didn't buy enough marigold seed this year for what I wanted to do so I bought a tray of them. They were supposed to be all yellow but I ended up with 1 plant that is the mahogany color

I would go with the errant seed in a solid colored nursery planting, also. Do not think that a solid colored seedling changed into the lovely peppermint. If you like them but it throws off your display, transplant them somewhere else and collect the seed in the fall or let them self sow for next spring. Or, leave them be and consider it a wink from mother nature.