Scottish Rock Garden Club Forum
Bulbs => Ian Young's Bulb Log - Feedback Forum => Topic started by: gote on October 21, 2008, 02:40:47 PM
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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
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A very interesting approach Göte !
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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.
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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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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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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? :-\
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As with colchicums, Lesley. Flowers in autumn and leaves in spring.
The variations of flowers and plants will be ever interesting to us.
Paddy
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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.
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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!!
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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.
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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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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.
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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.
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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.
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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.
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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...... ::)
I would suggest it would be foolish to expose your bits to the sky until they are ready. Ovaries are a nutritious food source so there is no point in putting your eggs in an obvious and visible basket until it is time for dispersal?
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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...... ::)
I would suggest it would be foolish to expose your bits to the sky until they are ready. Ovaries are a nutritious food source so there is no point in putting your eggs in an obvious and visible basket until it is time for dispersal?
Anthony - one of my Sternbergias currently has its bits exposed & I presume they are nutritious since they are being eaten by something.
Martin Rix has a not very illuminating discussion of the subterranean ovary in his book Growing Bulbs. He lists 22 genera which possess it & in which it probaby originated independently.
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Wonderful - now I have you all trying to solve my dilemma.
So often we are conditioned to think within certain parameters - but I always try and break the boundaries and look at all possibilities.
I have always assumed or been taught that autumn flowering bulbs are flowering 'out of season' unlike their spring relatives which are 'in season' but is this the case?
To broaden this discussion can anyone offer any reason why there are no autumn flowering fritillarias?
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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...... ::)
I would suggest it would be foolish to expose your bits to the sky until they are ready. Ovaries are a nutritious food source so there is no point in putting your eggs in an obvious and visible basket until it is time for dispersal?
Anthony - one of my Sternbergias currently has its bits exposed & I presume they are nutritious since they are being eaten by something.
Martin Rix has a not very illuminating discussion of the subterranean ovary in his book Growing Bulbs. He lists 22 genera which possess it & in which it probaby originated independently.
By there very nature, sternbergias have their ovaries on a stem. Crocus flowers have their ovaries under ground. The stem only elongates when the seeds are ripe, which makes sense.
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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...... ::)
I would suggest it would be foolish to expose your bits to the sky until they are ready. Ovaries are a nutritious food source so there is no point in putting your eggs in an obvious and visible basket until it is time for dispersal?
Anthony - one of my Sternbergias currently has its bits exposed & I presume they are nutritious since they are being eaten by something.
Martin Rix has a not very illuminating discussion of the subterranean ovary in his book Growing Bulbs. He lists 22 genera which possess it & in which it probaby originated independently.
By there very nature, sternbergias have their ovaries on a stem. Crocus flowers have their ovaries under ground. The stem only elongates when the seeds are ripe, which makes sense.
Anthony - sorry, I obviously didn't make my point clearly enough. I was wondering why, if it was a so advantageous, Sternbergias did not also have subterranean ovaries - though I believe S. clusiana effectively does. With respect to crocus, I also wonder to what extent the supposed advantages of subterranean ovaries are offset by the enormous distance the pollen tube is required to grow - up to 10cm or so.
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I have always assumed or been taught that autumn flowering bulbs are flowering 'out of season' unlike their spring relatives which are 'in season' but is this the case?
To broaden this discussion can anyone offer any reason why there are no autumn flowering fritillarias?
Ian,
I do not believe that there is 'out of season' or 'in season', I think it all relates to the competition after pollinators, in spring there are much more flowers around which makes a lower Chance for a bee to find you.
While in Autumn there are much less flowers and so you have a better chance, I think evolution created this separation of plants that had better results in terms of continuity of the species by flowering in spring or autumn.
As for your Fritillarias question:
Frits. have a soft bulb meaning it doesn't have a sufficient protection against drought, not as in the case of Crocus and most other geophytes that have layers of tunic, and so the solution is to go deeper and deeper in the ground,
for example,in the case of F. arabica [persica f. arabica], in the desert we once degged for a bulb that was 60cm deep in the ground.
Now, if it had to flower in Autumn , it means it would have to grow a stalk of at least 1.2 meters high, through a soil that is hard and dry as a rock.
Having a relatively small sized bulb i assume it would be almost impossible without available water.
Urgineas for example have a Hugh bulb that can weight a few kg [full of water] heaving the neck on the surface or just below and so it can afford blooming in Autumn.
My answers are only thoughts that I share and not scientifically proved...
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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...... ::)
I would suggest it would be foolish to expose your bits to the sky until they are ready. Ovaries are a nutritious food source so there is no point in putting your eggs in an obvious and visible basket until it is time for dispersal?
Anthony - one of my Sternbergias currently has its bits exposed & I presume they are nutritious since they are being eaten by something.
Martin Rix has a not very illuminating discussion of the subterranean ovary in his book Growing Bulbs. He lists 22 genera which possess it & in which it probaby originated independently.
By there very nature, sternbergias have their ovaries on a stem. Crocus flowers have their ovaries under ground. The stem only elongates when the seeds are ripe, which makes sense.
Anthony - sorry, I obviously didn't make my point clearly enough. I was wondering why, if it was a so advantageous, Sternbergias did not also have subterranean ovaries - though I believe S. clusiana effectively does. With respect to crocus, I also wonder to what extent the supposed advantages of subterranean ovaries are offset by the enormous distance the pollen tube is required to grow - up to 10cm or so.
The question is biologically irrelevant. You might as well say why don't Agapanthus have subterranean ovaries. If your ovaries start off underground, no point in exposing them too soon. That's the way these crocuses have evolved. There is not one solution fits all. Sternbergia flowers are on a stem clear and simple.
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The question is biologically irrelevant.
Well Anthony, I think that is debatable, but the pages of the SRGC forum do not seem an appropriate place to debate issues in theoretical biology.
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Oron, thanks for your thoughts on my Fritillaria question they are good points and I will think about them - but it is a fact that some fritillarias share the same habitat as crocus both summer and spring flowering so there is no simple answer.
I agree with you that pollinators must play a very big part in the evolutionary development of these bulbs and when they flower they are possibly more influential than climate alone.