Before the snowstorm arrived yesterday, and continues through today as well, I had intended to post this article on moonwort ferns, a very interesting group of ferns that not many people see. In a month from now on warm grassy fields the first moonworts will begin to emerge from dormancy and unfold their leaves to the sun. But first the snow must melt.
When warm spring weather arrives my life becomes especially busy. There are the gardens and the young apple orchard to tend, new trees to plant, my sheep and chickens, awful activities like mowing the lawn, and my work as a field botanist. Much of my field botany work is about finding rare plant species and that is actually how I became involved in it. One group of plants I am often asked to search for are a small ferns known as “moonworts”. There is a mysterious aura surrounding these ferns that affects some botanist-types, a few of whom become quite strange momentarily upon finding one.
My first encounter with the the odd little ferns known as moonworts was back in 1971 in a patch of wild strawberries many years before I had even considered botany. They were fleshy pale green plants with clusters of yellowish “berries” on a leafless stem opposite from a frilly leafy stem and were just a bit taller than the strawberry plants I was feasting from. I had a small book on ferns from Golden Press that said these were the daisy-leaf moonworts but that was about all. I don’t think I ever saw these ferns anywhere again for a long time. Years later I learned there were several species of moonworts and they were grouped in the genus Botrychium , a name derived from the Greek “botruchos” meaning “cluster” after the clusters of the little green “berries” (really spore-bearing bodies). Some of these moonworts were also very uncommon or even rare. The name “moonwort” (meaning “moon herb”) is from an Old English word for the species Botrychium lunaria which has leaflets that look like green half-moons. There is a lot of magic and folklore surrounding that species including its supposed power to pull out the nails from horseshoes and to open locks.
Moonwort ferns differ in many ways from plants we usually think of as ferns. The stems are small relative to the leaf mass, upright, fleshy, usually unbranched (only one growing point), and completely below ground with just a few thickened roots. The roots lack root hairs but association with mycorrhizal fungi may compensate for this. Moonwort ferns are ephemeral plants, the leaves appearing in the late spring or early summer and quickly senescing in a matter of a few weeks and then going dormant.
One leaf, or occasionally two, per year is produced by the stem. The leaves are small ranging from less than an inch to around 6 inches in height. The cut of the leaf can be very simple or very complex. The leaf is composed of two parts: a photosynthetic zone (“tropophore”) and a reproductive zone (“sporophore”). The tropophore may be thin to somewhat leathery to succulent depending on the species and may be divided with several to many divisions called “pinnae”. A very interesting aspect of leaf development is the production of successive leaf primordia (points of leaf origin). There may be as many as six leaf primordia, and a new one is formed every year. Thus, a leaf seen above ground during any particular growing season may have started its development as many as 6 years earlier. The other part of the leaf, the sporophore, is a slightly to highly branched structure, depending upon the species. It is covered with many fleshy, globular sporangia (structures that produce spores) that split longitudinally to release thousands of dust-like yellow spores.
The millions of spores produced by colonies of moonworts drift across the landscape germinating where conditions are suitable. The gametophyte (the sexual reproductive phase of the plant) is not like that seen in other fern species except Psilotum. Lacking chlorophyll, it is a white, subterranean, and irregular to cylindrical tuberous plant. The gametophyte of typical ferns is a thin, flat, green, usually heart-shaped plant that grows on moist soil and rocks.
It was once assumed moonwort ferns grew in special and rare habitats such as mature or old growth deciduous forests, moist soils, and similar places. But this is true only of a few species. One very tiny species, a variety of the least moonwort called B. simplex var. tenebrosum, grows in the moist duff and moss of cedar and ash swamps. Many other moonwort species grow best in open places such as in old fields with little shade from trees. A few, like the daisy-leaf moonwort and similar looking species, can be found in such places as old fields, prairies, sand dunes, railroad embankments, even spoil dumps at open pit iron mines. I have found the rare pale moonwort (B. pallidum) on sand dunes by Lake Superior, old fields, and the rubble piles of mine dumps. It is not unusual to find several different moonwort species growing at the same site.
Many moonwort species are rare and grow only in certain areas. Others, while a little more common or widespread are nonetheless seldom seen. The distribution patterns of some species show large gaps between known populations often several hundred miles apart. There are a few reasons for this. The fronds of moonwort ferns are small ranging from less than an inch to around 6 inches in height thus they are easily hidden among grasses and small herbs. Moonwort ferns are ephemeral plants appearing in the late spring or early summer and quickly senescing in a matter of a few weeks. So the time to find them is limited. Some populations seem to last only a few years in a place and then are gone. Why that should happen when it looks like nothing has changed is not certain. There is the possibility that the plants may have gone dormant for a year or two.
One spring day in 1994 while hunting for moonworts and their relatives the grapeferns (Sceptridium) in a blueberry patch I came across hundreds of morel mushrooms. A great find! And, by the way, I went back to that strawberry patch in 2003 and found the little daisy-leaf moonwort plants still there.