I have couple of questions:
*why pot in the pot?
*what kind of trees did the branches and stumps came from?
*were the leaves partially or well composted, and what kind of trees the leaves came from? (I know you showed some oak leaves, but were they all oak?)
*did you use seedlings of exactly same age & type? (looks to me that there are few different types of peppers & eggplants - was same number of same planted in each tub?)
*did you water all of them same or 'as necessary'?
*did you grow your other veggies in same tubs?

Hope I am not asking what you already answered.
The peppers & eggplants harvest looks good.

Thnx. Rina

What's you're interpretation of the physics here? Did the stump wick up the water to the surface such that there was no perched water on the bottom?

Rina,

*why pot in the pot?

This was just to divert any drainage to runoff the deck. Since I water with a drip system on timer and sometimes I travel, I didn't want the wooden deck to get wet.

*what kind of trees did the branches and stumps came from?

Soft wood, long needle pine. This wood, when dry, wicks very well and decomposes faster than hardwood. I should try it with hardwood to see if this really makes a difference or not.

*were the leaves partially or well composted, and what kind of trees the leaves came from? (I know you showed some oak leaves, but were they all oak?)

Good question. The leaf pot contained roughly equal amount of oak, redwood, and long pine needles. They were all dry, not rotted when first used. In the leaf pot the roots grew in the leaves quite well.

Whereas in the pot with just redwood needles in the bottom, the roots didn't grow into them.

This was a key observation. 2 difference accounted for this I believe. One: soil filtered into the leaves in the leaf pot, because sometimes I watered with a hose on the shower heading close to the soil just so the water stream would push the compost deeper. I watered more gently with the compost/leaf pot, so the compost didn't get pushed into the redwood needles at the bottom of the pot.
Second, long pine needles decompose quite fast. They had completely decomposed when I dug up the tub.

So the roots would not grow just into freshly dried leaves well. They did need some compost or soil. In the future I'll try 3 parts leaves (compressed volume), to 1 part compost.

*did you use seedlings of exactly same age & type? (looks to me that there are few different types of peppers & eggplants - was same number of same planted in each tub?)

The 3 peppers in each tub were the same age & type, I purchased these Burpee 6 packs that had 2 each of 3 different types of peppers.
The eggplants were different: Stumpot had Pot Black, Casper, and 2 Japanese. Branch pot had Black Beauty, & 3 Japanese. I planted 2 of the Japanese in each pot late in the season.

*did you water all of them same or 'as necessary'?

They were all on the same drip system, 12 emitters, 6 minutes a day. But I also hose watered about once a week. With the hose I watered the leaf pot more, since I knew it would dry out faster. I hose-watered the branch pots less.

*did you grow your other veggies in same tubs?
No. All eggplants and peppers were grown in tubs, rest of my vegetables were grown in-ground.

greentiger,

I do use 5:1:1 type mix for some indoor plants and they are much happier for it. I just have never been able to get good results outside on my deck with it. My own theory is that the roots don't form as much contact with the mix since it is highly aerated, so they can't wick up fast enough to prevent wilting in hot, sunny weather. In cool weather (<= 80degrees) or even in hot shade the plants do great.
Since my deck only gets afternoon sun, the 5:1:1-plants would just wilt and go into survival/bonsai mode and start fruiting early and stay small.
When I move in a few years to a place that gets morning sun, I'll try 5:1:1 outside again. I'm very interested to really understand difference I've observed to what I see you all are getting.

Zero cost fertilizer was used (HLF, homemade liquid fertilizer or human liquid fertilizer :)

About the wicking physics:
The 2" of soil right underneath the stump was wet and contained perched water. But the roots were great there, thick and white. Probably because they were right next to the drainage/aeration holes. Also they were receiving water that dripped down through the stump so it probably was a good wood-decay + HLF fertilizer slow drip.

The top of the stump would wick away any excess water.
The dry wood I used will wick up about 3" not more.
So water from the bottom of the tub would not wick up to the top of the stump. But the top 3" of the stump would provide water to the top of the soil as needed.

Overall the stump pot was easy to water and very robust. I could overwater it without negative consequences, and it could go for days even a week without water and the eggplants would be fine. They might droop a bit in the heat, but not go into severe wilt.

Cheers

I really do want to experiment with stumps now too. Thanks for documenting/posting this!