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Author Topic: Why do autumn crocus flower when they do?  (Read 5759 times)

gote

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Why do autumn crocus flower when they do?
« on: October 21, 2008, 02:40:47 PM »
A couple of weeks ago you Ian discussed the question:
Why do autumn flowering crocus flower in the fall?
Perhaps it is the wrong question maybe a better one is: why do they perceive fall as spring?
During my time north of Barcelona I noticed that, to some extent, the seasons were reversed..
In Sweden Polypodium vulgare gets new fronds in the spring when the hard days of winter are over. The very similar Catalonian Polypodium gets new fronds in the fall when the hard summer is over. Here the cold of the winter is the time to be dormant. In the south, the dry summer is the time.
Crocus follows the pattern dormancy - flowering – making seeds and forming a new corm – dormancy.
My belief is that autumn-flowering species are accustomed to dry-summer climate and start when the temperature drops (or whatever gives the timing) Spring flowering species are adjusted to cold-winter climate and start when the temperature increases.
Lilium candidum is next to impossible to grow in my area. Orchis, anacamptis and the lot are the same. These are accustomed to dry summers when they are dormant and mild wet winters when they vegetate.
The frequency of pollinating insects is of course also a reason but these are subject to the same constrictions so the reasons overlap
Göte
     
« Last Edit: October 21, 2008, 05:35:44 PM by Maggi Young »
Göte Svanholm
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Luc Gilgemyn

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Re: Why do autumn crocus flower when they do?
« Reply #1 on: October 21, 2008, 02:57:01 PM »
A very interesting approach Göte !
« Last Edit: October 21, 2008, 05:36:08 PM by Maggi Young »
Luc Gilgemyn
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Ian Y

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Re: Why do autumn crocus flower when they do?
« Reply #2 on: October 21, 2008, 06:29:29 PM »
I have considered your reason as well Gote and it could be that simple but sometimes I wonder with crocus if we are looking at an autumn flowering species that has modified and adapted to also flower in the spring.

The fact that the ovary stays under ground suggests that sort of strategy while all the other bulbs that have spring flowering relatives have above ground ovaries not best suited to go through a winter.
Cold undoubtedly plays a big role as you point out as does a warm dry dormany period.

Another factor that we need to take into account is that Crocus are in the family Iridaceae which probably has its ancesteral home land in Southern Africa around the Cape crocus has evolved as they migrated northwards.

I suppose we will never know the answer but it is fascinating to speculate and I look forward to any other comments.
Ian Young, Aberdeen North East Scotland   - 
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Anthony Darby

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Re: Why do autumn crocus flower when they do?
« Reply #3 on: October 22, 2008, 09:48:47 AM »
Göte is correct. Bulbs and corms are modified storage organs designed to tide a plant through harsh times. In northern climates, that is winter and the plants grow in spring, taking advantage of conditions before herbaceous plants take over. In Mediterranean-type climates this is summer, so growth is from autumn through to spring when the climate is mild and wetter.
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Maggi Young

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Re: Why do autumn crocus flower when they do?
« Reply #4 on: October 22, 2008, 03:40:41 PM »
Yes, we know what bulbs are intended to achieve from the plants' point of view, but I think Ian is meaning that we should look beyond that to a reason for the underground ovary etc...... ::)
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Lesley Cox

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Re: Why do autumn crocus flower when they do?
« Reply #5 on: October 22, 2008, 07:26:13 PM »
And assuming all the above is correct, why do some autumn crocuses flower with their leaves while other don;t make leaves until 4-6 months later? :-\
Lesley Cox - near Dunedin, lower east coast, South Island of New Zealand - Zone 9

Paddy Tobin

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Re: Why do autumn crocus flower when they do?
« Reply #6 on: October 22, 2008, 08:02:48 PM »
As with colchicums, Lesley. Flowers in autumn and leaves in spring.

The variations of flowers and plants will be ever interesting to us.

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Lesley Cox

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Re: Why do autumn crocus flower when they do?
« Reply #7 on: October 22, 2008, 08:36:14 PM »
Yes, but not always. CC goulimyi and serotinus salzmannii flower with leaves, nudiflorus and banaticus without. Why the difference? Besides, some colchicum flower with their leaves too. C. baytopiorum (in autumn) and szovitsii (spring) for instance.
« Last Edit: October 22, 2008, 08:38:55 PM by Lesley Cox »
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tonyg

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Re: Why do autumn crocus flower when they do?
« Reply #8 on: October 22, 2008, 11:25:13 PM »
Lesley - without having been to all the relevant locations my understanding is that C serotinus and C goulimyi would be unlikely to experience prolonged winter snow cover while C nudiflorus and C banaticus probably would.  In other words the crocus with generally lowland distribution/mediteranean type climate are more likely to flower in autumn, with leaves. ... Now I'm sure your next reply will offer some which do not fit this theory!!

Gerry Webster

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Re: Why do autumn crocus flower when they do?
« Reply #9 on: October 23, 2008, 04:10:49 PM »
Lesley - without having been to all the relevant locations my understanding is that C serotinus and C goulimyi would be unlikely to experience prolonged winter snow cover while C nudiflorus and C banaticus probably would.  In other words the crocus with generally lowland distribution/mediteranean type climate are more likely to flower in autumn, with leaves. ... Now I'm sure your next reply will offer some which do not fit this theory!!
While it seems plausible to suppose some connection between environmental conditions & whether plants are synanthous (with leaves at flowering) or  hysteranthous (leaves appear later) matters do not seem straightforward since many plants seem to have a wide distribution in terms of elevation but maintain a more-or-less constant pattern of leaf growth. Some details from BM:

C. laevigatus, sea-level - 600m(to 1500m in Crete), synanthous;
C. boryi, sea-level - 1500m; synanthous
C. tournefortii, sea-level - 650m; synanthous
C. banaticus; 130 - 700m, hysteranthous
C. medius, 200-400m, hysteranthous;
C. pulchellus, sea-level - 1800m, hysteranthous;
C. robertianus, 450-900m, hysteranthous;

It would seem that in order to draw any conclusions about the relation between patterns of leaf growth & environment one may also need information about localised snow cover, winter temperatures &, doubtless, other factors.
« Last Edit: October 23, 2008, 08:17:43 PM by Gerry Webster »
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gote

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Re: Why do autumn crocus flower when they do?
« Reply #10 on: October 23, 2008, 06:18:15 PM »
Since Mediterranean plants are very difficult in my climate I have not been able to observe as much as I would have liked to do.
How are the other "Crocuslike" plants doing? I mean where is the ovary?
I am thinking of the genera Lloydia, Sternbergia, Colchicum, Merendera They are not particularly closely related but seem to have adapted to the environment in the same way.

Plants adapt to the environment on an ad hoc basis, but they do not necessarily revert back in a new environment. If the adaption is not harmful in the new environment it does not necessarily disappear.
This is of course sheer speculation but if we assume that autumn flowering crocuses adapted to Mediterranean climate by starting the flowers as soon as the temperature starts to drop. We can then assume that some of those that ventured into harsh winter did not start flowering in the spring but rather postponed sending up leaves.
Speciosus is the only one I am certain that it survives my climate in the long run and it definitely has no leaves until spring.

It is interesting to note that I have gomulyii that came from central Europe and that one comes up with leaf earlier than one from Lithuania where the winter is harsher.

Göte
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Oron Peri

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Re: Why do autumn crocus flower when they do?
« Reply #11 on: October 23, 2008, 08:45:17 PM »
And assuming all the above is correct, why do some autumn crocuses flower with their leaves while other don;t make leaves until 4-6 months later? :-\

Lesley,

The answer is very simple...Snow!!!

For example: C. hermoneus, palasii, cancellatus and many others as well as some Colchicum  that grow at high altitudes flower in autumn, October-November, by the end of November snow covers the ground for at least 4 months, which mean that plants cant make photosynthesis and/or leaves would freez to death, there for they will set  leaves the minute snow melts.

Now, some Autumn crocus and Colchicum flower in early Autumn when temperatures are very high still and sun is backing. Since there was no rain yet, they would prefer saving the little water they still have in the corm and therefor they will bloom without leaves.

And the third group is the autumnal species that flower a bit later after there was already at least one good rain and so they can grow leaves without any risk of drying out.
« Last Edit: October 23, 2008, 09:38:20 PM by Oron Peri »
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Lesley Cox

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Re: Why do autumn crocus flower when they do?
« Reply #12 on: October 23, 2008, 09:54:19 PM »
Well thank you Gentlemen. My initial enquiry was somewhat tongue-in-cheek because I'd never really thought about it until this thread. The answers seem logical and confirm that there really ARE good reasons for all the small mysteries that the gardener encounters but (in my case) writes off as "what will be, will be."

It is very true, that old saying that the more one knows, the more one realizes one knows very little.
Lesley Cox - near Dunedin, lower east coast, South Island of New Zealand - Zone 9

Gerry Webster

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Re: Why do autumn crocus flower when they do?
« Reply #13 on: October 23, 2008, 11:08:33 PM »
And assuming all the above is correct, why do some autumn crocuses flower with their leaves while other don;t make leaves until 4-6 months later? :-\

Lesley,

The answer is very simple...Snow!!!

For example: C. hermoneus, palasii, cancellatus and many others as well as some Colchicum  that grow at high altitudes flower in autumn, October-November, by the end of November snow covers the ground for at least 4 months, which mean that plants cant make photosynthesis and/or leaves would freez to death, there for they will set  leaves the minute snow melts

And those at relatively low altitudes which are hysteranthous? And those at relatively high altitudes which are synanthous? Whatever the answer is, I don't think it is simple.
« Last Edit: October 23, 2008, 11:24:54 PM by Gerry Webster »
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Oron Peri

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Re: Why do autumn crocus flower when they do?
« Reply #14 on: October 24, 2008, 06:41:25 AM »
Gerry,

By answering 'simple' I was referring to Lesley's specific question.

My answer regards the Mediterranean species, If you  think of a certain Autumn flowering Crocus you will notice that most of them
can fit into one of the three categories  I have described.

I think in the end, it is all a meter of temperatures, rainfalls and pollinators.  I do think there are reasons for these phenomenons.
« Last Edit: October 24, 2008, 06:49:27 AM by Oron Peri »
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