Fun With Volunteers

[0soyoung]

Volunteer trees, that is.

Among many volunteer trees I’ve potted and grown, I started this group of three Norway maples in 2010 after having found them sprouted in my yard early in the spring of 2008. Sentimentality is the primary reason I maintain it - the mother trees are a few hundred feet away on opposite sides of my property. The mother of the green one is about 100 years old and the two red (‘crimson king’) mothers on the opposite side are about 40 years old – all sizeable, big leafed trees.

Aside from sentimentality, there are two things I find interesting about this group. For one, the color contrast in the summer becomes much more vivid in the fall (in the first attached photo). It is a nice little laboratory for studying leaf size reduction, for the other (illustrated by the other two attached photos with a leaf from one of the mother trees). With these, the top-most leafs tend to be largest with leaf sizes decreasing moving downward, toward the roots. Nevertheless, the top-most leafs never get larger than about 20% the area of the mother-tree leaf size.

 

[JudyB]

Sweet grouping. Nice coloration.

 

[Cadillactaste]

That is really interesting. The comment about the leaves being larger on top. I wonder if it has to do with getting more sunlight...thinking of how on some conifers you select and remove needles. Weaker branches on bottom because of less light? So don't really know...just something that popped into my head when I read your thread.

Great reduction from the mother tree to what you have going on with the bonsai...pretty cool indeed! Thanks for sharing.

 

[0soyoung]

The comment about the leaves being larger on top. I wonder if it has to do with getting more sunlight...thinking of how on some conifers you select and remove needles. Weaker branches on bottom because of less light? So don't really know...just something that popped into my head when I read your thread.

I love this kind of 'how do trees work?' stuff - glad you are intrested too.

I really don't think light is the cause, though it does explain why there aren't many leafed branches at the interior of the group. Generally, plants to adjust to sunlight (within one season) by adjusting the amount of chlorophyl and/or protective anthocyanins rather than changing leaf size. But more to your point, I have examined the mother trees and shaded leafs low on the tree are not appreciably different in size from leafs in sun much higher up.

I'm thinking the polar auxin flow is a key to the top to bottom effect:

• shoot tips and leafs are auxin sources
• buds and leaf growth are suppressed by a passing auxin flow

Hence the top (or most distal) leafs are in charge and become the largest because there is no other auxin flow to suppress their growth.

The fact that being confined in a pot reduces the leaf size in general is well-known but not well-understood. Current horticultural thinking is that this happens because of strigalactones that are produced in the roots and flow upward. Strigalactones are also thought to be the actual agent of the auxin flow suppression - all very involved (I'll be reading more about this stuff over the winter - this is entertainment for geeky me!).

This past season I just repeatedly defoliated the upper part of the trees (3 times, all told), starting as soon as the apical bud's leafs were semi-hardened and about as big as I would ever want them to be. The apical leafs of the crimson kings still grew 2x to 4x larger than the basal leafs. I didn't repot the group this year (and will not again next year in the belief that I can get further reduction without endangering the trees' general health).

 

[dick benbow]

Initially thought with the headline, that I was finally gonna meet you as you had joined the volunteers at the new curator and weyerhaeuser display in Federal way.
BUT

Alas, I was NOT disappointed. What a nice grouping and great color! Appreciate your sharing your experience. I'm trying to learn with vine maple....

 

[0soyoung]

Initially thought ... you had joined the volunteers at the new curator and weyerhaeuser display in Federal way.

As much as it appeals to me, Benbow-san, the Pacific Rim Collection is on the opposite side of Seattle and about a 105 mile, 2 hour drive away from my home - not bad for a bay-area CA commute, I suppose, but a bit much for volunteering.