A picture of four daisies posted by Twitter user @san_kaido is getting a lot of attention. Three of the flowers in the photo do not look normal. The typically round yellow centers bend and curve like pairs of lips pursed in displeasure. These mutants apparently grew in Nasushiobara, a city bordering Fukushima Prefecture, the region where reactors at the Fukushima Daiichi Nuclear Power Plant melted down after the earthquake in 2011.

Since other plants and animals have show the effects of radiation — bird populations near the closed power plant have shown mutations and population declines — many people jumped to the conclusion that these mutated flowers were evidence of frightening radiation levels.

Take a look at the flowers:

Mochizuki for Fukushima Diary translated the tweet. Here is the translation with minor grammar tweaks:

… (Nasushiobara City, 5/26/2015) The right one grew up, split into 2 stems has 2 flowers connected each other, having 4 stems of flower tied beltlike. The left one has 4 stems grew up tied to each other and it had the ring-shaped flower. The atmospheric dose is 0.5 μSv/h at 1m above the ground.

A writer for The Weather Channel reports that the described radiation dose, measured in microsieverts per hour, is classified as safe for "medium to long term habitation."

It’s easy to assume that the odd appearance is due to a dose of radiation. After all, researchers have shown that even tiny doses of radiation can mutate butterflies. However, this particular flower deformity pops up all the time, even if it’s a bit freaky-looking. The mutation is called fasciation, a word that means banded or bundled, explains Jackie Carroll for Gardening Know How. She writes that scientists think fasciation is caused by a hormonal imbalance, though that imbalance may be triggered by a number of things: insects, diseases or physical injury to the plant. Though it can’t be "fixed" once it has happened, a plant that regrows each year may come back perfectly normal after one year of fasciation. Sometimes the trait is genetic and can be passed to the next generation, but more frequently it is a one-time occurrence. And not all fasciation is bad. Carroll writes:

The fasciation of a fan-tailed willow makes it a highly desirable landscape shrub. Fasciation deformation of flowers such as the cauliflower-like heads of a celosia is part of the charm of the plant. Crested saguaro cactus, fasciated Japanese cedar, beefsteak tomatoes and broccoli are all examples of desirable fasciations.

At this point, no expert could say whether the daises became fasciated because of nuclear radiation or something completely different. The city and its mutant flowers are roughly 80 miles inland and south of the power plant. It is outside the 12 mile evacuation zone that displaced more than 12,000 people.