Abies balsamea 'Nana'

Abies balsamea 'Nana'

Saturday, March 15, 2014

Growing ferns from spores, aka: fern geek-out

One of my biggest concerns in moving across the country back to Washington state is safely transporting my germinated fern spores. Possibly my most prized possession at the moment is a container of tiny Cyathea dregei gametophytes. Cyathea dregei is a tree fern native to South Africa that is reputedly hardy to 7 degrees Fahrenheit (probably very optimistic, but there are several plants growing at the Royal Botanic Gardens, Edinburgh). However, being the plant-crazed lunatic that I am, I tracked down a source (Silverhill Seeds) of spore for this very slow-growing tree fern and I am going to attempt to grow as many as I can so that I can someday test them in the Pacific Northwest and hopefully share them with as many people as I can. For more information on this tree fern, see Ian Barclay's old angelfire website, here. This has inspired me to talk a little about ferns and their propagation.

This next part may be more than you want to know. Feel free to skip it. There's no quiz, so I'll never know.

Plants have a life-cycle known as "alternation of generations" consisting of sporophytes and gametophytes. The sporophyte is the diploid (2 sets of chromosomes) stage that most of us think of as a plant, since in vascular plants this has become the larger, dominant stage. (In mosses and liverworts the reverse is true, the gametophyte is the dominant, photosynthetic stage and the sporophyte is entirely reliant on the gametophyte for support.) The sporophyte produces gametophytes through meiosis (halving of the chromosomes) so that the resulting gametophytes are haploid (1 set of chromosomes), which will then combine to create another sporophyte with 2 sets of chromosomes. In flowering plants and cone-bearing plants, the gametophytes have been reduced to pollen and ovaries, which combine to produce seeds. Inside the seeds are embryonic sporophytes which will grow into the plants we are familiar with.

Back to ferns. In ferns (and their relatives) the sporophyte is the familiar, ferny plant that we all know and love. These plants produce spores, which germinate into gametophytes. The gametophyte is a structure known as the prothallus, a separate, often heart-shaped organism that is fully self-supporting and photosynthetic (unlike in flowering and cone-bearing plants). The prothallus produces sperm and/or eggs, which then produce a sporophyte. The sporophyte grows out of the prothallus, which dies once the sporophyte is large enough to support itself.

Had enough technical gibberish? Let's get on to some practical matters.

Unfortunately this is a retroactive post, so no pictures of the process of  sowing the spores. To germinate my fern spores, I used an empty, clear plastic salad container. A sterile, humid environment is key to success.


First, I thoroughly washed my salad container and wiped it down with rubbing alcohol for good measure (technically the first step was eating the salad to obtain the empty container, but I suppose that could be considered optional). I put my soil (for these particular spores I used Fafard seed-starting mix) into a spare nursery pot with drainage holes in the bottom. Then I poured boiling water over the soil until it drained from the bottom. This is a precautionary step to sterilize the soil and help prevent mold or other unwanted organisms from destroying the fern spores. After the soil had cooled, I put a 2-inch layer (probably more than I need) of the sterilized mix into my empty, cleaned salad container. Then I made an attempt to sprinkle the spore evenly over the soil surface.
Oh, look, green stuff on my soil! Not exactly evenly distributed, though I figured out the label on the container lid was contributing to that. I removed it and the center seems to be greening up a bit. 


Finally, I misted the the spores lightly with distilled water (tap water contains algae and other organisms that may compete with or harm your spores), put the lid on the container and placed it under my growing lights (oh, and waited, mustn't forget the waiting). The spores were sown on December 29, 2013. I noticed germination about the third week of February, 2014. At this stage, you can't really tell if you have fern gametophytes or algae, as the thin green tinge over the soil surface could be the beginnings of either one. As they grew, however, I began to make out the characteristic heart-shaped prothallus of fern gametophytes (Rather upright with taller stalks than other spores I've germinated, maybe because they're tree ferns? Just kidding.) In the past week or so I've been able to clearly make out the shape of the gametophytes, but they are still only a few millimeters tall and wide.



These little guys will take some time to look like anything, much less like ferns (and even longer to look like TREE ferns, if they make it that far), but it's so fascinating to watch them develop. Maybe they'll have trunks by the time I'm 40.

To start your own ferns from spores, you can collect fern fronds with mature sori (the spore-bearing structures, usually on the underside of the fronds). Do your research first. Learn what type of fern it is and how to identify mature sori so that your spores are ready to be collected. You can place your collected fronds in an envelope or on a sheet of paper with the sori-side down and allow it to dry. Once it is dry, discard the frond. The spores will have fallen into the envelope or onto the piece of paper and are now ready to be sown.

I wouldn't recommend this as a passtime for the impatient, but if you don't mind waiting it is a cheap and fun way to grow your own ferns and you can get some really unusual and rare types that may not be readily available as full-grown plants.

Have you ever started ferns from spores? Do you have a favored method or materials?

4 comments:

  1. Kudos to you, I've sown plenty of seeds, but have never tried fern spores. I hope your baby tree ferns make it to Washington alive.

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    1. It's so much fun watching seedlings (or sporelings) grow! I'm so nervous about transporting my fern spores. I also have a bunch of seedlings that will be riding in the car with me, packed with the utmost care.

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  2. You are certainly a very patient person! This was fascinating information! Thanks.

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  3. Glad you enjoyed it! Patience is a luxury oft wasted by the young.

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