Tap Root?

[Cajunrider]

In a practical sense: for bonsai purposes, does it matter??

Anything resembling a traditional bonsai pot is well shallow of the depth of roots "in the wild"...tap or not. That includes the seedling "tap root" that is working to establish the tree's survival.

Even when collecting, roots down to 2' or more need to be considered a possibility. That they don't go down 10' is irrelevant...they go down deep enough you need to open up a large enough hole you can cut them. And the root ball will still very likely be deeper than a bonsai pot and need further flattening.

For seedlings, you still need to manage a deeper-than-you-want-in-the-end central root from many species. Either that means trimming it and encouraging side shoots or putting it on a tile to force it lateral to keep roots "shallow".

One example: I recently received an order of 50 bald cypress yearlings. The "tap roots" on them were 8"+ long and rigid. Even at 1 year, the roots are too deep for bonsai use and need addressed...

Last week I pulled out a 6" base BC from next to a bigger BC. Since the main objective was to keep the big BC healthy, I couldn't cut the root surrounding the small BC. I tied some stout rope to the small 10 ft tall BC and pulled it right out of the swamp with my truck (not easy ). The tap root was 3" in diameter and 5 ft long going straight down.

 

[dbonsaiw]

Check out the Tree of Life in Bahrain. It is literally growing in the middle of a desert that gets little to no rain each year. People aren't exactly sure how it gets water. May have a massive tap root that found water.

 

[Shibui]

Starting to wonder if it has more to do with a process of desiccation rather than the air itself killing off the roots.

My point exactly. It is not air that kills roots, more a lack of moisture. Roots will grow through air just fine provided there's enough humidity. The idea that air pockets in soil will kill a tree is not correct.