Eric’s Pet Plant – Australian Tree-fern (Cyathea cooperi)

The Tree-fern in its new surroundings seems to be quite happy. There is a smaller one lurking to the left.

Big doings over at Yale’s Marsh Gardens. Our friend Eric is finally about to climb out of the greenhouse construction blues and ascend toward the greenhouse enjoyment oratorio. This week he starts celebrating, giving us the lowdown on tree ferns and inviting us to the grand opening.

Australian Tree-fern (Cyathea cooperi)

By Eric Larson

Before discussing the fern, I want to start the new year by saying these columns are not just about plants, the same way the Bible is not just about religion – not that I’m making any sort of comparison other than that. Although if I think for a minute (which is always dangerous), we could do an Old Testament about humanity’s relationship with plants and the environment, and a New Testament where we evolve into a more ‘loving’ or sustainable approach.

In the Old Testament, we were given dominion over the Earth and all that is on it. In the New Testament, we learn we are part of and not above all the processes and we share DNA with all living creatures, even the banana (some say 40%) for instance. Do you think seeing Avatar might have had an effect on me?

As we go forward, I’ll be talking about gardening in general; garden-related subjects (I wrote about water issues once, and there is a column on the way about honeybees); perhaps some cuisine and then certainly very unrelated subjects.

Once in a while, if I’m feeling cantankerous or devoid of my usual pithy plant banter, I will bring back the Colonel (British Army retired) and his wife Millicent, fictional characters based on old coots and their lovely wives everywhere. I somehow feel that writing about him will either help me avoid that fate or at least make me somewhat self-aware as I descend into it.

Now let me give you several invitations to join us at Marsh Gardens:

1. As advertised, on Friday January 29, 2010,  there will be a Grand Opening of the New Greenhouse.  This open house event will include tours of the glass houses, a ribbon cutting for the new greenhouse and desert display (which won’t be completely installed, but will be well on the way), live music, light refreshment and all of the usual fooferaw associated with our events.

2, Before that, we are having a couple of Pre-Opening Volunteer Days: Thursday, January 14, and Friday January 22. Both will be all day events, from nine to five, with plenty to do for anyone who has an hour or so to donate to the garden. Tasks will include general clean up, mixing soil for the Desert Display and weeding indoor plants. Sound fun? Well, if you didn’t get to the tropics for the holidays, now is your chance to get a few hours of warm humid sunlight on your face. And do a good deed for a good cause, as well as hang around with us.

3. We are planning a series of Seminars on Practical Beekeeping. New Haven beekeeper Vincent Kay, whose honey label Swords into Plowshares is sold at locally owned markets in the area, will be our instructor and leader. We will start in February and then meet quarterly, to cover all the seasons of bee culture.

The first session will center on general beekeeping issues, lifecycles, types of bees, etc.  In subsequent sessions, we will offer practical bee handling advice, possibly with bee-suits so that we can have several people present when we open the hives. We will have a specific date for the first one in the next column, so please stay tuned.

CONCERNING THE FERN

After the completion of our new greenhouse, the long process of populating it with plants began.  This week we have started moving large plants into the first room of this greenhouse, with an emphasis on ‘ancient plants;’ plant families or species that have been around for a long time. Cycads, ferns and other foundation plants for the history of evolution are represented in this area, along with other more ornamental plants for aesthetics.

One of the first plants we moved in was our large tree-fern, Cyathea cooperi. This native of Australia is a fast grower, which causes some concerns in areas where it has become invasive. Another story of an introduced species running amok to scare the botanists around the campfire. In Hawaii for instance, this species has taken over huge expanses of the Big Island.  On a visit there some years back, I stayed in a cabin nestled amongst a tree-fern/camellia mixed forest. Charming but not biome-friendly.

Ferns are evolved from an ancient lineage that reflects pre-flowering plant reproductive systems.  Ferns propagate by spores, usually on the undersides of the fronds or leaves. The term ‘tree-fern’ refers to a group of ferns whose fronds are elevated on a trunk, sometimes as tall as fifty feet or more.  There are a number of families that include the morphological type we call ‘tree-ferns,’ and many genera.  They all belong to the order Cyatheales.  The genus, family and order names are derived from the Greek, kyatheion, meaning ‘little cup,’ referring to the cup-shaped sori on the underside of the fronds. (Sori are the part of the fern that produces the spores.)

Tree-ferns in general prefer tropical or sub-tropical rain-forest situations, and even the  hardy types belong to the genus Culcita, found in southern Europe. So for us tree-ferns are a hothouse undertaking.

If you grow one in a pot you can move it from the patio to the sunroom, but there is one caveat that should be kept in mind.  The tiny hairs on our species, and many other tree-ferns, are very abrasive to the skin. They get into your clothes through the tiniest openings, work their way into your skin and will often remain there for days, even through showers and baths.

Don’t fiddle around with this fern unless you and your clothing are well protected. Notice the fine hairs on this fiddle-head and frond stems.

Please bundle up tightly in as airtight a garment as you can find when moving, pruning or otherwise handling your plant.

My entire crew clad in white Tyvek suits, looking like a throw-back to Ghostbusters: Who you gonna call for ghost-busting or tree-fern handling? We are ecstatic that we had just finished moving the specimen you see behind us. For some reason, one of us is wearing 3-D glasses. Another serious day at the botanical garden.

As for its care, a tree-fern prefers light shade if kept outside over the summer, but as much sun as you can give it in the glass house or sun room.  Water well daily except during the winter, when a bit less is necessary to keep it healthy.

Fertilize on a weekly schedule during the spring and summer, but make it less frequent in fall and winter as their growth slows down.  Not much ails a tree-fern, although we noticed some mealy-bugs on ours when we moved it.  But it doesn’t get completely infested as many plants do.  A good going-over with a cotton swab dipped in alcohol will take care of that little problem for the (well-protected!) home gardener with only a single tree-fern to manage.

In lieu of growing one yourself, please stop by for a visit with ours.

Disclaimer: The opinions and views expressed herein are the sole responsibility of the author.  Yale University and Marsh Botanical Garden and Leslie Land are not responsible for the inane and sometimes off the chart craziness of this publication. Contact us at: eric.larson@yale.edu or at (203) 432-6320.

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20 Comments »

  • Phoebe Said,

    Can I ask what you are using to fertilize your Tree-ferns?

    I live in Australia and I have lots of tree ferns in my yard and I have never fertilized them, they are in a shady area and get watered daily.

  • Eric Larson Said,

    Good morning, Phoebe. We fertilize with 20-10-20 soluble Peters fertilizer. Some growers suggest a 3-1-2 proportion of the NPK trinity. Unlike most herbaceous ferns, Tree Ferns respond to and really need the extra fertilization, at least under the conditions and with the soil mix that we use.(We grow them in large pots in our greenhouses, in a mix of peat moss, perlite and vermiculite) We fertilize every two weeks, providing about 150-200 ppm N.
    A couple of things I didn’t mention: mealy bugs and spider mites can be problems for these plants, although not many other insects seem interested.
    And this plant is native to the rain forests in Queensland, Australia. Malaysia and Indonesia are significant in their numbers of species, as are Central and South America.
    Happy growing, Phoebe, and watch out for the tiny hairs.
    best,
    Eric

  • Phoebe Said,

    Many thanks for the reply Eric.

  • Louisa Cunningham Said,

    If I remember correctly, it is the
    > Ostrich fern that produces the fiddleheads people eat (if so inclined)? I was also told that fiddleheads actually aren’t the best thing nutritionally for humans. Having lived in the country in Japan, part of the pleasure of spring is rejoicing in the flavors of renewal represented by the fiddlehead with a touch of soy. Would you know if nutritionally this is a good or bad thing? Or would you know a reliable source for such information? I’m not sure googling is the best approach to such a question. Thank you

    Hi Louisa,

    I took your question to heart. The answer is here.

  • Chance Said,

    Have an Australian tree fern growing for about 5 years was 2 ft, now 12ft+. The spores are ridiculous, can watch them fall even after blasting the ting with water. Makes a mess! Any ideas on how to control the spores?

    Yes it’s Summer.. It’s going NUTZ!!!!!

  • where can cyathea cooperi be burchased, i’m stoked.

  • Eric Larson Said,

    I’m not sure how one would control the spores. Disrupting that part of the plant’s physiognomy, especially the ‘ancient’ plants might be an interesting subject for Monsanto to take on. (Only kidding: no money in THAT research, as opposed to the so-called ‘suicide seed’)
    As for sources for Cyathea cooperi, Dave Garinger, our Tropical Plant Curator, says that this species is the most common, and is available on-line, which is where he gets it when he needs a replacement. Which I should say isn’t often. Our trees have produced numerous spores, which germinate with alacrity.

  • dan kleck Said,

    Can I cut an Austr. tree fern back at/near the ground? Mine are too tall, but I don’t want to damage them…just get them back into the shade below.

  • Manohar Said,

    Hi!
    What’s the difference between Dicksonia Fibrosa and the Australian Cyathea cooperi?
    Thanks.

  • Tracy Maclean Said,

    Just how bad are the hairs, I have been considering a tree fern for the front porch, but it would have to be moved for the winter. What is the temperature range for these strange critters. I live in Central Texas about 45 miles SW of Austin?

  • Eric Larson Said,

    First to answer Manohar, Cyathea and Dicksonia are very closely related, both being in the Cyatheacea family. Beyond that, I could only say that Dicksonia is more primitive, a more ancient plant. (Have you heard Cole Porter’s song, “I Want a Primitive Man?”) I don’t know if the hairs on Dicksonia fibrosa are as difficult as on Cyathea, but they could only be half as bad and still be disruptive to the pruning and general handling process. Tracy, don’t let that discourage you, though. I’m not sure of the plants cold hardiness, but I have seen forests of them growing way up in elevation in Hawaii, where it gets quite cold at night. Put one in a pot and move it in during the coldest cold snaps. Just wear something you got at goodwill and then throw the garment away: the hairs get in the laundry too. Good luck, all!

  • doorothy Said,

    I was given two lovely australian tree ferns, right before a cold snap hit the south! I had no room indoors. They are on a screened porch. All the fronds turne brown. Icut them off. Will I see new frons appear soon?

    Welcome, Doorothy,
    and I wish I had more encouraging news, but everything depends on how cold the snap was and how long it lasted. C. cooperi is sub-tropical, likely to perish at temps in the 30’s even above freezing, so your plants are probably goners. That said, if the ferns are in big pots and you’re in zone 9 b or warmer, might as well wait and see what happens. Individual plants can be tougher than they have any right to be.
    Good luck!
    Leslie

  • Fred Garcia Said,

    My tree fern is now some eight feet tall. Is there a way trim it back, lower it, and have it be ok? I asked my local nursery and they said cutting the truck would/ could kill it. Want to possibly cut back as it now over the garage. Hoping you get back to me, Fred

    Unfortunately your nursery is correct. Reducing the size of a tree fern is ending its life. Start or buy a new one and plant it nearby, thus ensuring that when the offending specimen comes down, you have a larger replacement.
    Eric

  • Linda Byrd Said,

    When and how do you prune the tree ferns?

    Hi Linda,
    Sorry to say the answers are “never” and “don’t.” Please see Eric’s advice to your fellow questioner, above.

  • Billy Said,

    Hello Eric,

    I just purchased my first tree fern, did all the research beforehand and asked the questions I needed answered but have been bugged by something the saleperson told me and have been trying to varify all day: I headed into the greenhouse pretty early and noticed they had their tree ferns sitting in water (not a standard pebble tray.) I asked if this was because they had just been watered or if if he suggested this practice. He assured me that they prefer that much moisture and this would be the best method for growing in my home. As this is so unusual in plant care (except carnivorous and bog plants)I would greatly appreciate a second opinion before either drowning and drying out the plant. Thanks so much.

    Hi Billy,

    I’ve forwarded your question to Eric – who’s having a very busy week this week – and will post his reply when it comes. Meanwhile, everything Eric wrote in this post suggests that standing in water is not only unnecessary but also a bad idea, especially when the plant is resting. There’s a big difference between keeping soil moist and keeping it sopping wet!

    • Billy Said,

      Thanks! I’m glad I went with my gut. I had only left it in a saucer of water for 12 hours before convincing myself not to and the difference is clear. The first day, a new unfurling frond, recurled the opposite direction and all the individual leaves did the same thing. As soon as I placed it in a dry saucer the “reverse curling” stopped and finally, after a few days, it seems to be bouncing back. I do look forward to hearing Eric’s response to this (maybe it really is a practical solution in a hot, sunny greenhouse but, clearly not a good idea in the home enviornment.) On a side-note I would like to express my gratitude for this site. I had just discovered the plant a few weeks ago at one of my favorite nurseries and had been doing the research anyone would do with a new, unusual houseplant. To my dismay, there is not a whole lot of information on the net about Australian Tree Ferns (especially as houseplants,) at least not without a little digging. I have to give you my highest praises and thanks for this little chunk of e-gold. To have a site with such great information to start with AND then to supplement it with people who are knowledgable and “on-top” of things, is such an invaluable resource. I don’t think I would have initially purchased my Australian Tree Fern without the guidance of this site.

  • Eric Larson Said,

    First I have some more nuanced answers to Linda Byrd’s request for information about pruning: In late winter, you CAN prune actually all the fronds off the tree fern, but you can’t appreciably lower its height. You can lower it somewhat by doing the following: Take it out of the pot. Cut through the below ground stem severing a portion of the lowest root mass. MAKE SURE TO LEAVE SOME ROOTS ON THE STEM. You can’t take all the roots off. How much you leave is a matter of feel, but the plant will need roots to continue to live. Then bury the stem in the pot adding soil above the old soil line: the tree fern will send out roots from the stem that is in contact with the soil. This will lower the overall size by the amount you have cut off, but this can’t be done every year to keep a plant in check. It’s done every three to four years.
    As for the tree ferns in a container of water: Billy, you are correct, it is a function probably of full sun and dry relative humidity: the plant uses all the water through evapo-transpiration. But this is dangerous technique for most of us: they just don’t like their roots swimming in water. So let the water drain through and treat as a regular potted plant.
    My very best to you all, and thanks for the kind words about the site, Billy. I’m proud to be a part of it from time to time.

  • Teresa Said,

    I have serveral tree ferns and wonder if breathing the spores can cause lung problems?

    Hi Teresa, interesting question – and one to which there appears to be no clear answer. Here’s what Eric had to say when i put your question to him:

    There is a wide diversity of opinions on tree fern spores and the effects on humans. While there are some who maintain there is little effect on humans, folks from Australia say that Tree fern spores are ‘like asbestos on steroids.’ Which doesn’t sound too salubrious to me. I guess the best approach is to be cautious. Just as some of us are allergic to mold and others not, certain kinds of pollen irritate some of us more than others. Some suggest that spores from Tree ferns and some kinds of bracken are actually carcinogenic. Others will say that ANY powder or substance when exposure is at a maximum will be irritating and even cause cancer as a result of long term exposure. If you are growing your tree fern indoors, it might be good to isolate from living quarters and the kitchen or the nursery. If you are blessed to be living in the tropics or sub-tropical regions, grow tree ferns where you can look at them but keep them downwind on the prevailing wind patterns from the house.
    If you are subject to allergies, best not to grow one.
    Sorry to hedge my bets so obviously, Teresa, but without definitive toxicological study results, that’s the best I can do.
    Best,
    Eric

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