More Mysteries: Growing Ferns from Spores

Prothalluses grow from spores on rock wool

Thirteen months ago I sowed spores from several types of ferns onto blocks of rock wool, photographed the process, and wrote about techniques for starting spores to grow baby ferns. The post is called, Unraveling the Mystery of Growing Ferns from Spore.

I ended up with more than a dozen zip-lock bags seeded with spores that I tended to all winter in my office, under lights. By the time the weather warmed in late April, there wasn’t the smallest bit of green to show that any of the spores had begun to grow.

Rock wool newly sown with spores in September of 2021

I was tempted to chuck all of the bags in the trash as a failed experiment, but decided instead to fill one of my large plastic boxes, normally used for starting Caladiums in the spring, with some potting soil and just move all of the blocks of rock wool into the box. I poured the remaining spring water from each bag onto the soil, covered the box with its tight fitting lid, and put the whole thing in a shaded, protected corner of the deck. And it has been there ever since.

It has been quite a summer. Soon after this, I injured my back while moving some pots, and that sidelined me from normal gardening for several weeks. As I was healing from that, finally, a close family member had an accident and I spent some time staying at the hospital with them, until they passed a few days later.

That all unfolded in the midst of a dry spell and heatwave, and the extent of my gardening revolved around trying to keep things watered enough for them to survive while I was dealing with the shock. The rest of the past several months has been something of a stressful blur.

But I did check on the progress of growth in the box in June and was delighted to find a bit of green. At least some of the spores had begun to grow. There were a few tiny plants plastered up against the side of the box that gets the most light. I added a little rain water and closed it up tightly once again.

Growth by October 19, 2022

When I began collecting this season’s spore in late summer, I decided to sow them differently. I went with the old, accidental method that worked for me at first. I put a few inches of fresh potting soil into a shallow plastic box, sterilized it with with some boiling water, and then sowed the spores directly onto the soil. I closed the whole thing up with a sheet of thin plastic held with a rubber band, and put it in a shady spot on the deck. Well, it bloomed green with new growth in only a few weeks time. I’ve been using that method again and again these past few months with different varieties of ferns. So far, a bloom of green prothalluses proves that everything is alive. I also have several boxes of sporelings growing on now in various sizes and stages of growth.

The volunteer sporelings in the garden keep my hopes up.

I checked the box of rock wool cubes once more, a bit later into the summer, to see if it was still moist, and finally pulled the whole box out of its corner again yesterday. When I lifted the lid, I was happy to find clusters of little gametophytes and even a few sporelings. And even some of the rock wool cubes further away from the light show green growth. It has taken much longer than I expected, but a good crop of sporeling ferns is on the way.

These sporelings are growing on in a larger container. I transplanted them out of their original propagation tray earlier in the summer. They are from spores collected in 2020.

I decided to leave well-enough alone. I had some fresh rainwater on hand and watered all of the blocks of rock wool and clusters of gametophytes to encourage more growth, covered the box, and put it away in a brighter spot. All of the ferns are hardy, so I’ll expect the sporelings to survive outside until we get into some seriously cold weather early next year.

Nature, and natural processes, remain a fascinating mystery. All of this just demonstrates, yet again, that patience is the first and best skill a gardener needs to learn. By giving those spores sown on rock wool the gift of time, they have come along when conditions proved favorable for growth. It may be another year before they have grown enough to plant them out into a bed or to pot them up to give away. But I believe that the day will come when the sporelings will be ready to leave their box and grow on as beautiful ferns.

If you love ferns, and want to try growing your own, don’t hesitate to experiment until you find the method that works for you, and for the fern species you want to grow. Just plan on it taking as long as it needs to take, cultivate your patience, and enjoy the process as each step unfolds.

Volunteer sporelings are growing in the moss in shady parts of our back garden.

For More Information:

Hallowell, Barbara and Anne C. Hallowell. Fern Finder: A Guide to Native Ferns of Central and Northeastern United States and Eastern Canada. ‎ Nature Study Guild Publishers. 2001.

Hoshizaki, Barbara Joe Hoshizaki and Robbin C. Moran. Fern Grower’s Manual: Revised and Expanded Edition. Timber Press. 2001.

Olsen, Sue.  The Encyclopedia of Garden Ferns. Timber Press. 2007.

Rickard, Martin. Ferns for a Cool Temperate Climate.  The Crowood Press.  2021.

Steffen, Richie and Sue Olsen. The Plant Lover’s Guide to Ferns. Timber Press.  2015

Visit the Hardy Fern Foundation’s website for additional information on propagation.



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