Northwest Palms

The problem with Cyatheas

Cold-hardiness is not just a matter of finding your coldest temperature during the year. It's also about any given plant's ability to sit tight and remain in a defensive mode of stasis during that part of the year when dangerous weather threatens. Some plants do this easily. Others do so reluctantly and some not at all. All plants respond to one or more different triggers that tell them it is time to grow. Warmth and photoperiod are perhaps the most common, but plants that are adapted to Mediterranean-type precipitation cycles often respond to moisture -- which means that winter is the season that they flower or otherwise deploy their reproductive mechanisms. They want to set seed (or spore) and get the young seedlings (or prothalii) off to a good start while there is still available soil moisture.
Cyathea cooperi seems to be one of these. It will frond in wet weather even in the dark and cold of mid-winter. So while it may survive in Zone 9 conditions, damage to the unfurling croziers is a danger where mid-winter temps are likely to dip below freezing. Tightly-wound croziers seem fairly durable. After the fronds are fully pinnate and hardened off, the fronds can put up with mild freezes. But even light freezes during the unfurling crozier stage is likely to fry the pinnules. Here are some New Year's day photos of Cyathea cooperi and Dicksonia antarctica showing the Dicksonia's superior adaptability with regard to winter dormancy.

The following thread was started by Steve in Brookings on January 07, 2007 at 10:16 pm PST

Here are the unfurling croziers of C. cooperi -- the crown is always quite exposed, and the fronds are especially tender at this stage. These fronds seem to have a death wish as they will be at peak vulnerability for this Thursday night's freeze.

The above followup was added by Steve in Brookings on January 07, 2007 at 10:19 pm PST.

The Dicksonia keeps its fronds tightly compacted inside a protected crown. Notice, too, how the funnel-shaped crown naturally collects the insulation of fallen leaves. I suspect that this is an evolutionary adaptation that aids in cold-weather survival. This fern will not start to frond until photoperiod and/or warmth instruct it to do so -- March to April and continuing on into summer. Ironically, my Dicksonias got more damaged than my Cyatheas last year, because the cold weather that we did get came late. I should mention that I don't think the winter fronding of C. cooperi is necessarily the standard for the genus. C. dealbata seems to be in stasis. C. medullaris isn't doing much yet, either.

The above followup was added by Steve in Brookings on January 07, 2007 at 10:25 pm PST.

Great shots, Steve. I had a large C. cooperi in a pot. I grew it up to about 4' trunk from a one gallon and I never saw it exhibit that growth in winter. I bet Portland's winter is cold enough to preclude that kind of growth(?). It was killed in 2004...just didn't take it in the garage...didn't think it'd get that cold. ugh.

The above followup was added by Steve in Portland z8b on January 08, 2007 at 6:12 am PST.

On NWCN they said it was going to be 65f in brooking today 12/8. I can see how tree ferns could get damage down there.
In warmer winters Dicksonia will grow here also in winter. Not this year yet. Nice Pics Steve.

The above followup was added by Roger on January 08, 2007 at 10:08 am PST.

Not all Cyatheas do that... just the tropical and subtropical ones. I would expect the hardier C. australis, C. smithii and C. dealbata to behave like D.a. with a more seasonally defined growth pattern. C. medullaris, however, will make fronds at any time of the year as long as it is not too cold, just like cooperi.

The above followup was added by Ian on January 08, 2007 at 10:44 am PST.

I think that's exactly right, Ian. And it isn't just the timing issue. The structure of the crown itself is just so much more exposed in C. cooperi and medullaris.
Unfortunately my C. smithii crapped out on me last year - I looked at it the wrong way and it said good-bye (actually, it got too dry in February and was dessicated if you can believe such a thing...who waters their plants in Feb.?). C. smithii seemed very well adapted here, it's one of those thermophobic plants that actually dislikes heat units and those are always the plants I go to first. It also has the protected crown structure like DA's do. But I don't think its appearance justifies its expense and putting up with its prima-donna attitude. Everyone I showed it to asked "What's special about it?", and I was hard pressed to come up with an answer other than, "Hardly anybody in this country has one." It's not surprising that it never really made it into the trade...kind of scruffy-looking actually. I also have hopes that C. dealbata will take the wind beatings (if I live long enough to see a mature one). I think it's one of the best for the southern coast, its procrastinating ways not withstanding. When it comes to the wind issue, it's easy to see why DAs are the only TFs to make it into the trade north of SF. Others might be hardy enough to withstand the occasional freeze, but a big sail of wind-catching fronds on top of a skinny trunk isn't the right engineering for 100 mph wind-burst resistance. As much as I'd like to try C. cunninghamii, for example, I don't know if I have a spot protected enough for it to escape beheading. My firm favorite, though, remains D. squarrosa and I'm hoping its colonial habit will allow it to come back from the occasional toppling of individual trunks.

The above followup was added by Steve in Brookings on January 08, 2007 at 11:18 am PST.

Looks like it will be a sunny day w/a high of 60F in town here. matt

The above followup was added by matt on January 08, 2007 at 1:07 pm PST.

Hi Steve nice to see a few tree fern pics in January I too find C.cooperii seems to have a death wish unfurling croziers in winter but can just about stop it with a straw cage but mainly to get it through my z 8b climate.

This pic shows my slightly fried Cooperii against D. antartica trunks which are a fantastic green still and normally stay green throughout winter.

I have a 2 foot C.smithii to go in the ground this spring so what sort of postioning would you say was best..........I have been told out of the wind for sure.
What sort of zone are you doing it in?

Kev

The above followup was added by Kev Spence on January 08, 2007 at 2:37 pm PST.

The said plant.

kev

The above followup was added by kev Spence on January 08, 2007 at 3:12 pm PST.

Kev, now that I see your comely specimen, I'm inclined to thing otherwise about their appearance. That's a beaut that you got ahold of. Is that an imported plant? Mine, as you can see, is looking a bit peaked.

The above followup was added by Steve Bismarck on January 11, 2007 at 10:38 am PST.

Hi Steve
Thanks for the pic and I have gotta say that is one unhappy tree fern...........is it still alive?

The one thing I have learned about these ferns ,from others, is that they do dessicate easily in the wind and could do with all round wind protection or at least protection from the prevailing wind.
I am intending to plant mine out in the spring , on my first pic, just behind the ivy to the left of the pic in a small hollow behind the D.antartica.

We have a guy on the UK Oasis moving to New Zealand soon and he is selling up and I am going on a round trip of probably 400 miles to pick up a trunked Cyathea dealbata and Dicksonia sellowiana C.gleichenioides but unfortunately probably cannot get his 6 foot trunked Cyathea australis in my car.
Can you pick tree ferns up easily in your area or not.

As regards to my C.smithii it was just a lucky find ina nursery over here and I assumed it was imported as per usual.

Kev

The above followup was added by Kev Spence on January 11, 2007 at 2:06 pm PST.

Kev, all tree ferns sold in the U.S. are grown from spore, and you would have a better chance of finding a gold dubloon on the beach than finding anything other than D. antarctica or C. cooperi at a commercial nursery. There is a rare plant nursery in Portland that has from time to time has sold me some plants from "the back", i.e., plants that were not placed out for public sale. That's where I got my C. dealbata and C. smithii, but they were small. There is a large botanical garden in San Francisco (Strybing Arboretum) that has a sale once a year that focuses on ferns and rhododendrons and they often have some rarer tree ferns. As for my C. smithii...what you see is what I have...Mr. Smith has gone to glory. It is pathetic, I know, that I cannot resign him to the compost heap and keep his tragic remains in the garden even now. It is a sad indicator of the depth of death-denial and separation anxiety that the disease of pterophilia imparts to those afflicted with it.

The above followup was added by Steve in Brookings on January 11, 2007 at 3:44 pm PST.

Well, the "death wish" of crozier unfurling when a bit beyond what was expected. The forecasted freeze was far more damaging than expected. The older fronds as well as unfurling ones were all burnt. But even milder areas in southern California saw crown toasting on cyatheas in this freeze event. At any rate, here's a before-and-after pic of the subject frond.

The above followup was added by Steve in Brookings on January 30, 2007 at 7:12 pm PST.

I have a number of Cyatheas here in the uk,i was told that c,cooperi would require winter protection,do you protect your cooperi during winter steve?

regards graham

The above followup was added by graham wright on July 25, 2007 at 1:16 pm PST.