Acorns to Oaks

Leaves Afloat

Oak Leaf on the Move

As the snow blankets the earth, there are patches of orange, rust and brown painting the mostly naked forest. These leaves cling to the tree, only being freed by harrowing winter winds or warming days of spring pushing out the new leaves.

Acorn Caps

I am embraced by the quiet serenity of this place, contemplating a mystery afoot which is perking my curiosity throughout my winter walk in the park. Only the sound of the leaves rattling above my head keeps my inquisitive focus. Stillness is not a part…

Look at it go….

As my attention is drawn to the lone oak leaves dancing across the new fallen snow, pirouetted on pointed end, making their way to the ice capped banks blown free of the glistening white blanket.

Wind Whipping

Above, the brown, supple leaves, still clinging to the tree in February, rustling as the wind whips through are a testament to an ecological development since the very first evergreens graced our planet. In fact, try to crumple leaves of oak and beech. Dry, they don’t even break into pieces. This springiness was why they were used in stuffing mattresses rather than using straw which was easier to collect, yet compressed easily. Early settlers were very  industrious and inventive.

There are the evergreens such as pine, hemlock, spruce and fir which retain needles all winter, yet not all conifers are evergreen to lose needles in winter, such as larch and bald cypress.

There are the deciduous trees such as maple, birch and cherry that shed their leaves to expose their very stark nakedness.

Japanese Maple Leaf on the Move

But not all trees in this forest are naked in their winter glory.

There is this odd group in the middle, composed of beech and oak. And, I am assuming larch and bald cypress as well. The question then becomes, is retaining dead leaves an evolutionary and ecological advantage for a tree that is in between? Why do these trees delay shedding when there is apparent benefit for doing so for others? Most tree species have picked a side. Either evergreen or not.

Being evergreen is believed to be an advantage to a tree by increasing the time available for its leaves to remain photosynthetic. They also reduce nutrient loss associated with dropped leaves and seal themselves to protect precious water.

Weighted Down with Ice

A deciduous tree has developed a redesign to allow trees in changing environs to reduce water loss and avoid frost damage during most unfriendly seasons. They then are increasing their photosynthetic efficiency during favorable seasons. So what is it called being in the middle…

The term is called marcescent. Which in laymen terms, is when a plant part dies and is not shed. The leaves may curl in a chrysalis-like fashion, but they hang on like a scared child gripping his mother hysterically on the first day of school.

Off again…

Young Oak

A botanist may say or agree that marcescence is a juvenile trait for a tree and it is usually observed on a young tree, but it also occurs on the lower branches of older trees.

Older Oak with Marcescent Leaves on Lower Branches

There is an idea that perhaps this acts as a means of trapping snow at the base of the tree, allowing for more moisture come springtime. But also consider that snow-covered branches weigh down more heavily on a tree and limbs may break as a consequence, so this can be a double-edged sword for an oak if you follow this logic.

Following the two leaves bouncing across the ice and snow has yielded little damage.

Other theories suggest that the retention of leaves may provide frost protection for new buds and twigs to weather out the winter, shielding them from biting, brutal winds.

Browser with a tasty belly full. Yummy on those yews.

Yet, others have suggested that the dead leaves act as a deterrent to browsing deer preventing the buds from being eaten. All plausible theories giving credence to marcescent leaves being helpful to trees living in dry, cold, deer ravaged forests.

Many Young Oak at the Base of the Mother Oak, a lot of busy squirrels.

But it is also possible the oak is an example of a tree that is evolutionarily delayed in development, not quite being a full-fledged deciduous tree.

Above you can see how successful the oak is in perpetuating itself. Oaks outcompete other species in areas that are dry and less fertile. And another theory suggests a reason why. It is proposed that by retaining the leaves until spring, the tree delays the decomposition process, enabling it to provide mulch and compost for itself and its offspring, thereby warming and fertilizing the less than optimum soil. This is when the saplings and the mother tree need the most nutrients and then get a quick jumpstart to the season.

Leaf Buds and Leaf Loss

So it appears to be a matter of great timing, shifting the competitive balance of one species over another. Very cool stuff.

Get some air…

Beech and oak are delayed in some respect to being full-fledged deciduois because, they are decendant from their more evolutionary, evergreen past. Beech, genus, (Fagus), and oak, genus, (Quercus), are in the same family , Fagaceae, which includes evergreens such as live oak and tanoaks.

Big Oak with Younger Oak on Either Side

Does anyone really know the reason why marcescence occurs?  It is understood how it occurs.  The abscission layer, separating a leaf and its twig, forms a seal in autumn on a tree.

Abscission at Dark Area, (I am Guessing) Andrea will Know

This switches off the leaf from its water and nutrient supplies like a gate valve, causing the leaf to usually, and in most cases, disengage. The base of the leaf stem produces an enzyme which forms this separation layer or abscission zone to help prevent infection and the tree starts the process of leaf drop.

Two Leaf Stems Attached, See New Buds?

The abscission layer is not fully formed with marcescent leaves. Simple, sort of until you consider the hormonal changes necessary, then it becomes all kinds of complex.

The hormone that stimulates abscission is called ethylene. It is believed that the hormone auxin inhibits abscission by preventing the abscission layer from forming.

For some science in less than sciencey terms, see my popular post Why Do Trees Change Different Colors on the Same Tree?.

Papery, Yet Still Springy

I hope you enjoyed the papery textured leaves in there whithery best. They bring a lot of winter interest to the landscape and you have marcescence to thank.

And if you missed my winter interest piece, here is the link. And for those that really like winter photography, I have a post sure to please. My coldest shots yet, plus more very red birds. This time the boys. Please stop back for my monthly GBBD Magazine for the 15th. Cold Niagara here too.

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About Garden Walk Garden Talk

I love to photograph, paint, draw, design, garden, travel the world, and pass on a few tips and ideas that I learned through experience as a Master Gardener and architect. I am highly trained in my field and enjoy my work each and every day. I garden in Niagara Falls, NY in zone 6-B. Find me at: http://gardenwalkgardentalk.com
This entry was posted in Conifers, Deciduous, Did U Know, Friday at the Falls, garden, Identification, Tree ID, Trees, Winter and tagged , , , , , . Bookmark the permalink.

35 Responses to Acorns to Oaks

  1. Donna says:

    fascinating science and you make it easy to understand…

  2. Mesmerising photos of leaves on snow Donna, how on earth did you take them? You must have got cold knees?!

  3. Masha says:

    I am glad I found your blog. Your post is very informative. I have been so engrossed in shrubs and perennials, it was shock for me to come here and realize how little I know about trees. It is such a joy to meet (even virtually) someone as knowledgeable as you are. Your photographs are excellent, I really enjoyed pictures of leaves and their shadows in the snow (just as I was taking pictures of spring for my own blog!). You must be a skilled photographer to freeze the motion of moving leaves and get such sharp pictures.

  4. Marguerite says:

    Donna, what an interesting article. I had no idea there were deciduous trees that held on to their leaves, let alone there was a whole other category of trees. Blogging makes me learn something new every day.

    • Hi Marguerite. It really is not a category exactly, just a little background on the trees development over a very long time that brought it to this point. It is also about Beech and Oaks relationship to each other. I checked many sources to try and lay it out as simply and concisely as I could. I am sure a botanist could clarify this much better.

  5. Great post Donna! It is fascinating to understand the characteristics and habits of trees. There is a reason for all they do. I love your poetic leafy shots!

  6. Edith Hope says:

    Dear Donna, What a fascinating account you give here. I have never before known why Beech hedging retains its leaves but that is why it has been a long term favourite of mine for creating a garden boundary. As you show here, I love the russets of the tones and tints of the Beech leaves and one is never without something of a screen whatever the season.

    • Beech are some of my most favorite trees. I like them in all seasons. I should have went to the farm and photographed them in the fields. I did have an image of a Larch I forgot to upload. They are not so pretty in winter form, but that is just my opinion.

  7. Missy says:

    I never knew, or more accurately, never thought about this class of tree. It’s fascinating.

    • Missy, it really is fascinating. Not many people notice these trees hanging onto leaves through winter. It makes you wonder how the trees developed this way and why. I found scientific research debunking the theories, but also saw some in favor of these explanations. It always makes me wonder how much we really know and understand. I think when science writes a paper, there are ten others questioning the findings.

  8. Donna, I love all the fascinating facts about what plants do and why. Especially enjoyed the photos of the leaves skipping across the snow–it felt like I was there. CarolynsShade

    • The leaves skipping was what made me post this. I have always been amazed by trees keeping their leaves. And, if you try to pull marcescent leaves off the tree, it really takes a tug. Try it sometime in the dead of winter. They are strong little buggers.

  9. Bom says:

    Very interesting post, Donna. Very nice captures of the floating leaves as well. No frost bite, I hope.

  10. Cat says:

    Such beautiful captures Donna and interesting science too. We just got back from Colorado where we had 32″ of snow fall during our stay! I can appreciate how cold you must have been waiting for the leaves to stop blowing!

  11. One says:

    Hi Donna, This is interesting. I would think the leaves are there to protect the young. At the same time, they are not ready to let go…

  12. p3chandan says:

    Interesting post and such lovely shots of that oak leaves dancing and pirouetting on the ice!

  13. Greenearth says:

    Beautiful images.

  14. Darla says:

    Nature is fascinating, is she not? I will never fully grasp all that is involved and why the plants do what they do…I just appreciate it. You have captured the mood of ‘peacefullness” wonderfully in these photos.

  15. That is an extraordinarily good post.

    Esther

  16. Absolutely gorgeous photos! Love the maple leaf — it’s like something from Fantasia. Also, thanks for the new word. I’m now repeating “marcescent” over and over in my mind to try and make it stick.

  17. Rosie says:

    Hi Donna, don’t know whether you are aware of this Stylish Blogger Award going around or not, but I find it an interesting game of tag…someone awards you and you pass on the award. I would like to extend this award to you for more than the style you have as a blogger. I think that you have style in the way you interact with fellow bloggers with grace and warmth. Please do come and collect the award from my blog. At the same time, we get to learn a little bit more about one another. It is fun.
    Rosie

  18. b-a-g says:

    Hi GWGT,
    I have never awarded 5 Blotanical picks so far but I think you deserve it for :
    (1) Making us think about something we haven’t thought about before
    (2) The science bit – and for making it easy to understand
    (3) Exposing yourself to such freezing cold conditions
    (4) Amazing photos – which tell the leaf’s story so well
    (5) Photo of the disinterested deer – not so keen on the marcescent leaves

  19. What an interesting post Donna. Most of our oaks here are primarily evergreen, but we do have some other trees whose leaves cling to them for dear life through winter. In my first garden, I remember having a Japanese maple that would always have brown leaves clinging on as the buds were breaking in spring. I found it so unsightly, I’d usually pull them off 😉

  20. debsgarden says:

    Very interesting post! We have a number of large oak trees on our property. Just this morning my husband and I were discussing this very thing as we looked out our kitchen windows to a large oak not far away. It still has all of its brown leaves. It amazes me how they can all be there and then one day I get up and poof! New leaves are coming out and all the brown ones are gone.

  21. Karen says:

    Another great post, Donna. Oak trees are my favorite of all deciduous trees but for some reason, I have none planted on the farm any longer. This is something I want to change though I will never see them grow to maturity. I wish I had thought of planting them when we were in our 20’s. The photography is wonderful, as always.

  22. lula says:

    Donna, You have captured the “dancing leaves in the snow” a visual poem!

  23. Andrea says:

    Oh my…Donna, you put me on the spot! hahaha! I felt like i am again undergoing a comprehensive examination. But before tackling the topic (or while i am still thinking to bid time), a short speech first. I would like to tell you that all the genus and species of trees you mentioned are not existing in my patch of earth! Second, i haven’t seen most of those trees you mentioned. I’ve seen an oak once (i dont know what kind), in the rocky mountains of Turkey, it must be very old because maybe >1m in diameter! Lastly, we dont have those gymnospersm in the tropics, only angiosperms. Moreover, i am a little bit of a plant physiologist, not a botanist nor ecologist, actually retired plant physiologist because now i am a patent agent. hahaha.

    Oak is one of the oldest trees, to be exact, one of the oldest angiosperms, million years ago they are already here. So maybe with that length of time they are already the most ‘learned’ or ‘wisest’ among them. So they have acquired the system to help them most, basically to survive harsh environment for the survival of the species. By being still here till now, their survival mechanisms could have worked efficiently for them. And maybe the foremost mechanism is the state of ‘marscescence’. (This term i also just heard or read in journals before, but didn’t really explored, i just know it goes with C3, C4, CAM, regarding photosynthesis mechanisms). They experientially learned to delay abscission of their petioles till spring, so they can withstand winter better. And you are correct (doing your homework well), they transmit more auxins to more parts of the body to antagonize ethylene-the dehiscence hormone, and several biochemical metabolic pathways come in: lignin, chitin, etc, etc. The mechanism is a complex process and i tell you it is a bit difficult, years or courses in college, graduate school, haha! The main objective of the plant is to survive winter in a dry environment.

    Donna, i am already getting lost! What is the question or topic you throw at me? Never mind, suffice it to say that it is juvenile characteristics because most young trees have it, while old trees have it only at the lowest portion, of course the lowest portion is the juvenile phase. It is logical that juveniles need this mechanism as they need more things to survive compared to older ones. Leaf abscission is a physiological response to dry conditions, and may not occur if water is perennially available. I don’t know what to write next. ..am sorry for this attempt. but i am glad you gave me an exam, i was able to dig my archive!

  24. Andrea says:

    oh i just realized it was so long. BTW, i am sorry again, oaks are angiosperms. Our gymnosperms are pines and some junipers.

  25. Here is an update from Andrea. Please go to her current post too for the whole thread.
    http://abagillon.blogspot.com/2011/02/succulents-agaves-and-bonsais-plus.html
    Regarding the photo of the abscission layer in your post, yes it is the darker part which has already separated, because it has lignified completely, thickened and dried completely, without any more water from the previously attached tissues. The abscission zone is complete in that area. The light part might probably be in transition and not dried yet. By lignification, that means hardening of the vascular tissues, e.g. a vegetable or let’s say an okra when left at ambient conditions for sometime will not be good anymore as a vegetable, coz it becomes tough. That toughness is due to lignification.

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