How hoarfrost forms

One of the most beautiful times during winter is when frost builds up on tree branches, blades of grass and fences.

The whole world takes on a bright, shimmering white hue, and it makes the bitter temperatures worth it. You might even call it a winter wonderland.

hoarfrostopens IMAGE file

This type of frost is called hoarfrost and can look like white feathers growing on a variety of surfaces.

It starts with water vapor or fog --- the gaseous version of water --- hovering over the ground the is at a maximum of 32 degrees. Because water freezes at 32 degrees or below, the water molecules in the air will come into contact with the freezing ground, a freezing branch, a freezing blade of big bluestem, a freezing metal arbor and will immediately turn from gas into a solid state as an ice crystal.

(Are all snowflakes unique?)

The more moisture that is in the air, the more the ice crystals will interlock on freezing surfaces and will build larger and larger into those feather-like frosty structures that we see in the beautiful outdoors. These large accumulations of frost is what is called hoarfrost.

hoarfrost on plantsopens IMAGE file

If there is not enough moisture in the air, hoarfrost will not occur.

Do you know why it's called hoarfrost?

Hoar comes from an Old English word meaning gray, venerable or old, and it was put with this kind of frost because it apparently made people think of an old man's beard. Hoary is still used as a term for something that is gray or white with age. Other things in nature are also called hoary, like hoary vervain. This purple flower has a leaf that is covered in whitish hairs.

(Butterflies and moths love vervain!)

hoarfrost on brushopens IMAGE file


Animal winter camouflage

The Iowa world is white in winter, so it makes sense that animals would want to blend in with their seasonal surroundings. Some animals have natural coloring that allows them to hide well in winter, whereas some animals change their colors to keep hidden from predators. Jackrabbit Jackrabbits used to be common in the tallgrass Read More »

Read More

How animals survive the winter

Humans often hole themselves up in their houses to survive the winter in front of the fire with hot chocolate. However, animals have to survive the frigid chill outside in the elements, and they have different ways of dealing with the change in seasons. Let’s take a quick look at how these Iowa animals survive. Read More »

Read More

Eight snow facts you probably didn’t know

All snowflakes are unique, sort of. The short answer is, yes, because each ice crystal has a unique path to the ground. They will float through different clouds of different temperatures and different levels of moisture, which means the ice crystal will grow in a unique way. Temperature and humidity – moisture in the air Read More »

Read More

Plants protect themselves from the winter cold

Each autumn, the world outside is getting ready for a change. Birds are migrating to find warmer wintering grounds. Mammals are eating a lot to increase their fatty insulation and are putting food away for the winter. Trees are dropping their leaves and going dormant. (Read about that here) What about other plants though? How Read More »

Read More

How prairie plants disperse seed

As a kid, we all picked a puffy dandelion and blew the wisps into the air. Little did we think that we were actually helping dandelions disperse their seeds. Dandelions and other plants only survive when their seeds are dispersed so that new plants grow the next season. They spread through a variety of ways Read More »

Read More

Prairie plant roots help water quality

Native prairie plants make wonderful habitat for wildlife like voles, turkeys, rabbits, ground squirrels, hawks and foxes. They provide both habitat and food sources for tiny creatures such as monarch butterflies, bumblebees and milkweed beetles. They are beautiful to look at. However, they are also important in a way that we can’t see. Deep down Read More »

Read More

Spring and winter coloring page

When you sit down to color a picture, it’s usually pretty obvious what you’re coloring. What’s fun about folding pictures is that you have to finish it before you can see exactly what you’ve done. As we transition from winter into spring, we thought it would be timely to create a folding picture that encompasses Read More »

Read More

10 snow activities you haven’t done yet this winter

You’ve built snowmen. You’ve gone sledding. You’ve had snowball fights. Now, it’s still winter and you don’t know what else to do to have fun in the snow. So we have put together 10 activities that will make the everlasting snow a bit more fun! Maple taffy I love historical fiction, and I grew up Read More »

Read More


  1. Reecie A Woodley on September 15, 2019 at 7:28 am

    I was reading the bible how God rained down manna which was small as hoar frost. Wanted to know what it looked like. Exodus 16: 14. thank you.

  2. Michele on December 11, 2018 at 1:36 pm

    Thank you! It is so beautiful, and now I know the rest of the story. It is a great trivia question and answer.