Defoliate Chinese Elms

[AlainK]

Portugal? I'm guessing by the sidewalk bricks

Yes!

My son worked in Lisboa for a year and I went there in october last year. I discovered that the small paving stones are a real feature in most of the places, even small towns we went to.

He's been in Belfast (NI) since July now, not really the same kind of weather, but the people are friendly there, that's what his brother who's just back told me.

 

[Adair M]

Fair point! However, as a scientist, you should acknowledge that even this evidence is anecdotal. We don't know (or has not been posted yet in this thread) why or why not from a biological standpoint.

I did. I said that a complete defoliation might harm interior branches. When the tree produces its replacement leaves, it’s going to put them where they will regrow the fastest. Which is out near the ends of the branches. Because they will have more exposure to the sun.

 

[markyscott]

Fair point! However, as a scientist, you should acknowledge that even this evidence is anecdotal. We don't know (or has not been posted yet in this thread) why or why not from a biological standpoint.

OK fair enough, although all this is fairly off topic from the OP as that was concerning fall defoliation, not what I’m going to talk about now.

While a deciduous tree is in leaf, it is absorbing light, CO2 and H2O and, through a set of reactions, producing a stable organic compound - glucose. At the end of the season, plants begin to move sugars and carbohydrates from the leaves to the roots to nourish the plant during the winter months. Whatever is left over after the winter is the reserve that the tree has to push growth in the spring. When spring comes, trees take a big bet and invest most of these sugars into pushing new foliage. The bet is that these leaves will last long enough that the investment will pay off and the tree will get its sugar back with interest. When you defoliate, you are making sure that the bet doesn’t pay off - the tree is forced to leaf out with whatever additional reserves it had left over after the spring push. Generally, that’s not much - that’s what Ryan was referring to as “a punch in the gut”. You’ll get a reduction in leaf size after defoliation to be sure - the tree is weakened without a lot of reserve glucose and carbohydrates, is unable grow strong, large, healthy leaves, and it won’t give you long extensions. Defoliate again and you’ll get even smaller leaves because the tree is weaker still - or maybe you’ll kill it.

Why don’t I defoliate trees in development? Because a weak tree with little leaves is exactly the opposite of what I want! I don’t care if it’s an elm, a maple, an oak, a ficus, or a bougainvillea. I want strong, healthy growth with big leaves and big extensions that I can wire into place throughout the growing season. When I prune, I want a big drop in auxin levels to encourage back-budding. All that growth is extremely important for building branches and it will take forever if you’re pinching and defoliating all the time because it weakens the tree. That’s the whole point of those techniques - to weaken the tree so that it produces little leaves and doesn’t grow too much. For a tree in development (and in the US, that would include almost every broadleaf bonsai that I’ve seen here), the trees need primary, secondary and tertiary branch development. Weakening the tree through defoliation before this is accomplished is really counterproductive. After branch structure with good movement and taper is in place one can start worrying about refinement techniques to build twiggy growth and tiny leaves.

So many times I’ve seen trees where people have put the cart before the horse and started pinching and defoliating before they built their trunk and branches. The result is consistent - terrible branch structure. Ramrod straight taperless branches with a poof of leaves out at the end and no interior ramification. When I’ve bought these trees it’s been for the trunk - I generally cut all the branches off and start all over again from the beginning. Tons of the progressions I’ve posted on this site are exactly that.

Scott

 

[0soyoung]

I love it, Scott - put a big ear-to-ear grin on my face . I owe you a beer! For that I have a Mastercard. This is priceless!

But I cannot help myself. Trees aren't potatoes.

At the end of the season, plants begin to move sugars and carbohydrates from the leaves to the roots to nourish the plant during the winter months.

Storage is as starch rrains in the vacuoles of living cells throughout the tree.

 

[markyscott]

I love it, Scott - put a big ear-to-ear grin on my face . I owe you a beer! For that I have a Mastercard. This is priceless!

But I cannot help myself. Trees aren't potatoes.

Storage is as starch rrains in the vacuoles of living cells throughout the tree.

Starches are just long chains of glucose molecules. But I stand corrected about the storage - you’re right that sugars are not just stored in the roots.

S

 

[milehigh_7]

Starches are just long chains of glucose molecules. But I stand corrected about the storage - you’re right that sugars are not just stored in the roots.

S

In fact, a good deal the of the fuel for the initial push of spring leaves is stored in the actual buds in the fall. That's why you can remove much of the roots (like the tap) and the tree will be just fine as long as most of the buds are left intact.

 

[markyscott]

Let’s talk about later - after the tree is out of development and into the refinement stage. Why don’t I completely defoliate the tree then? Adair touched on it - it has to do with balance.

We’re all familiar with how we “balance” a two-flush pine like a Japanese Black Pine. There are tons of books that describe various iterations of the technique. Basically they all describe weakening the strong shoots and strengthening the weak shoots. We do this by needle plucking and decandling. We pluck more needles from the strong shoots and fewer from the weak ones. And/or we decandle the weak shoots early or not at all and the strong shoots later. That way the weak shoots have more time to develop and the strong shoots less. I don’t think I’ve seen anyone questioning this because it makes such intuitive sense - I mean, why would anyone want to pluck a bunch of needles off of shoots that are weak already?

So what about broadleaf trees? How do we balance them? Well - we have different techniques. Pruning and selective leaf removal. If we want to weaken a strong shoot, prune it back to a weak one, or cut it off entirely. During the summer when we remove leaves, remove them from the strong branches and leave them on the weak ones. It’s the moral equivalent of needle plucking on pines and that is how balance is achieved on a broadleaf tree. Any broadleaf tree, anywhere on the planet where broadleaf trees grow. How does this relate to defoliation? Well there are different types of defoliation in practice.

1. Complete defoliation. This technique is the most stressful for the tree and it weakens everything - both the strong and the weak branches. I never do this. Defoliating the weak interior growth can kill it. It’s the same as pulling lots of needles off of weak interior shoots on a pine tree. These interior buds are incredibly important - I’m trying to strengthen them, not weaken them. Defoliating weak shoots weakens them further - it’s the opposite of what I want.
2. Individual branch defoliation. This I do all the time, especially with apically dominant trees. Sometimes even with trees in development there’s an area that will get out of hand. Defoliation is a very important technique for slowing down apical growth while encouraging basal growth.
3. Partial outer canopy defoliation. This I do all the time on more developed trees. This particular technique involves removing the outer layer of foliage while leaving the inner, more delicate leaves untouched. This is the least stressful defoliation technique to the tree because it can continue to photosynthesize through the process. It also allows light and air through the the outer canopy into the weak interior shoots. They get strengthened while the strong shoots on the outer canopy get weakened and the tree is brought closer to “balance”. So why defoliate completely when we can use the technique instead? It looks like this:

Sometimes parts of the tree get developed more quickly than others. When you have a branch or two that needs to be developed more, one can perform a partial outer canopy defoliation on the tree, but leave the branches that need to be developed alone. Like this:


Weaken the strong and strengthen the weak - that’s our goal on developed trees. So why ever do a full defoliation? It is A) the most stressful for the tree and B) weakens all shoots uniformly - both the strong and the weak. Instead, I do a partial outer canopy defoliation leaving leaves on the weak interior shoots intact while weakening the apical shoots so that they don’t take over. It’s less stressful to the tree and helps balance the strength between the shoots.

So I made two posts 1) why I don’t completely defoliate trees in development and 2) why I don’t completely defoliate trees in refinement. Do I have any exceptions? Of course. I will completely defoliate strong and healthy trees if:

1. I plan to put them in a show. Some tropicals will flower if defoliated at the right time. Sometimes I want to show a broadleaf tree without any leaves. Sometimes I want to show a broadleaf tree with a fresh set of small leaves. There are lots of asthetic reasons why one might want to completely defoliate for display.
2. In the fall when the colors begin to change. At that point the tree is slowing down. Chlorophyll is being replaced at a slower rate and other pigments called carotenoids begin to show through giving a yellow/orange/red appearance to the leaves. Leaves may safely be removed at this point.

Scott

 

[Anthony]

I understood that you guys defoliate to encourage fine branches and smaller leaves.
So I guess for you fall - might - make more sense.

For us - say Tamarind ----- feed well first for a month and defoliate at the end of the dry season - May /April
when the Tamarind trees in nature are self defoliating.
The budding is so heavy, you have to use a skewer to remove the extras.

The seagrape also self defoliates and responds as above.
Which is why on the test trees we do leaf counts. 3 inches tall and almost 60 leaves.

Some like the Fustic, defoliate to soil dryness.

Our local willow leaf ficus is also self defoliating.
BUT I have never seen a defoliating Ficus B.

Thus far a month of fertilising works well on all species down here before a
defoliation is attempted.
The Zanthoxylum [ Satinwood ] will die back if the last leaves on a branch is
defoliated.

Interesting how Bonsai techniques are advancing.
Good Day
Anthony

 

[twisted trees]

Defoliated late spring. Looks fine to me.

 

[markyscott]

Defoliated late spring. Looks fine to me.

View attachment 173205

If you’re happy with how this tree has responded to defoliation and it’s progress, then that’s all that counts and I’m happy for you.

Scott

 

[milehigh_7]

Defoliated late spring. Looks fine to me.

View attachment 173205

"looks fine" is not very scientific O.

I think what @markyscott was saying is that it could be better with different techniques.

@markyscott thanks for taking the time to explain what you were saying. It makes sense and is very appreciated.

I still say this has been a great talk! Thanks, everyone!

 

[twisted trees]

If you’re happy with how this tree has responded to defoliation and it’s progress, then that’s all that counts and I’m happy for you.

Scott

I capice your thoughtful post.

This was very vigourous when I defoliated and as you can see in the pic I still have sacrificial branches and good overall vigour. I'm pleased with the developmental results.

 

[Jpour6]

Trying to read through all these comments and have a simple question ..
is it safe to defoliate a Chinese elm in early January with leaves already turning color and dropping? I would like to better visualize the structure and do some pruning/wiring.

 

[hemmy]

Trying to read through all these comments and have a simple question ..
is it safe to defoliate a Chinese elm in early January with leaves already turning color and dropping? I would like to better visualize the structure and do some pruning/wiring.

Nice tree! I like the slant form.

It is wild that it took until post 17 to answer the original question. In SoCal, you can follow Scott’s advice in that post:

“When my elms started to turn at the end of December, I defoliated them.”

When I lived in SoCal, I’d defoliate maples around Christmas but their leaves would be more “spent” than the elms. I often wouldn’t defoliate Chinese elms (mostly due to laziness). Some of your leaves are turning, but others still have sugar/starch to return. You can defoliate unless you think it needs additional energy reserves based on prior growth or conditions. You can also just partially defoliate which should let you see the structure.

Stay safe!