I am instantly attracted to the sight of ferns growing in the woods. Their graceful and elegant foliage makes them so appealing. Take a moment to think about how they reproduce. It’s not the same as other perennials in the garden because they don’t have flowers. So how do they do it? Ferns have a fascinating form of reproduction that is a bit of a mystery to even the well seasoned gardener.
To learn more about the reproduction of ferns, read the article below by Terrestrial Ecologist, Dave D’Entremont.
Ferns are strange, strange plants. After all, what kind of plant doesn’t have seeds!?
Ferns occupy a funny little niche in the plant family tree, having diverged into a separate group after the evolution of vascular tissues (“plant veins”, for simplicity’s sake), but before the evolution of seeds. This means they can grow taller than mosses and other bryophytes, but still reproduce a lot like them – totally backwards!
How does it all work?
Spores (single plant cells) are produced in tiny structures found on adult fern leaves – either underneath normal fronds, or sometimes clustered on special fronds dedicated to making spores. These spores disperse by wind and water to damp soil, where they germinate and grow.
But do spores grow straight into ferns? No, that would be too easy! It’s not simple like seeds.
Each spore has only one copy of each chromosome – half the genetic material necessary to live as an adult. In effect, sexual reproduction hasn’t even happened yet! Instead of adult fern fronds undergoing sexual reproduction like flowers do, this task is left for new baby plants the spores grow into!
Baby ferns, or “gametophytes”, are tiny algae-like leafy proto-plants with three jobs: grow a tiny leaf, soak up sun, and wait for just the right rainy conditions. When the right conditions occur, rainwater allows the gametophytes exchange gametes, and only then does sexual reproduction finish. This process, which can take months depending on the species, leads to the growth of the sporophyte – what we recognize as the adult fern fronds.
At Royal Botanical Gardens, we have a wonderful diversity of fern species growing in our nature sanctuaries. This year, we decided to undertake some propagation of select native fern species for specific habitat restoration projects.
The spores are growing and off to the races – thought we would share a few photomicrographs of the tiny gametophytes of that first growth stage!
By: Dave D’Entremont