American pillwort facts for kids

The Pilularia americana, also known as the American pillwort, is a very unique type of fern. Unlike most ferns you might know, its "leaves" are mostly just stems. It belongs to the aquatic fern family called Marsileaceae. This family also includes the water clovers and other interesting water plants like Azolla and Salvinia.

What is the American Pillwort?

The American pillwort, like all other water ferns in the group called Salviniales, has a special way of making spores. It creates hard, seed-like cases called sporocarps. These sporocarps are different from its close relative, Marsilea. In Pilularia, they are round like tiny balls, while in Marsilea, they are flat.

Another interesting thing about Pilularia ferns is that they have lost their flat leaf blades. What's left looks like grass-like stems, called a stipe. Even though they look different, these plants still have the classic fern way of unrolling new leaves, which is called circinate vernation. This means new leaves unroll like a fiddlehead.

Where Does the Pillwort Live?

The American pillwort is commonly found in many parts of California and south-central Oregon. However, it's only found in a few scattered places in eastern North America. It's hard to know if this is because it truly grows in only a few spots, or if it's just very hard to find. This fern is small and looks a lot like grass, so it's easy to miss! You often need to look very closely to be sure it's a Pilularia.

This species also grows in Central and South America. But scientists are still studying these plants. They might actually be a different species called P. mandoni A. Braun.

Recent studies have shown that the P. americana plants in North America are actually two different species that look very similar. Most of the plants in the United States are true americana. But plants in southern California and Mexico are genetically very close to the Australian and New Zealand species, Pilularia novae-hollandiae. They might even be considered part of that species someday.

How to Grow the American Pillwort

This plant is quite easy to grow if it has the right home and isn't too crowded. The pillwort might disappear during drier or colder times of the year. But don't worry! It can grow back the next year from its tough sporocarps.

Even though it's an aquatic fern, it prefers to grow in shallow water with its stems sticking out into the air. It can also grow completely out of the water. However, it always likes to be rooted in wet mud.

Images for kids

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  Map showing the distribution of Pilularia americana.

See Also

• Pilularia