What exactly do you mean by "weakest".........weak wooded and prone to breakage? Shallow rooted and prone to blow-down? Not very disease or pest resistant?

I mean the ability to stay alive. Without storms doing something or pests. Just the raw ability to stay alive. Which one is the weakest this way?

That would depend entirely on location. Trees that struggle to stay alive in one location may thrive in another. It would be impossible to narrow it down to a single species that would react the same way regardless of where it was grown.

Since many birches are native to vast stretches of the northern part of the US, it would hard to consider them 'weak', although not necessarily very long lived. And peaches grow very well in many parts of the country as well - California, Georgia, South Carolina, New Jersey and eastern Washington state, for example.

Everything is adapted to somewhere.

all plants have the ability to stay alive.. or they would have been edited out of the gene pool millions of years ago ..

I disagree I have a Colorado blue spruce that is 40 years old and it has not been phased by anything. It has gone through months of drought with showing any signs of weakness. I quit watering a birch for three weeks and it died.

"without" showing signs of weakness.

Simple, birch trees grow along rivers. Blue spruce would die in marsh conditions. Neither is weakest, they just grow in different environments.

You would say cacti are tough, but two days in a marsh would probably kill many of them. Ok, then water hyacinths are tough because they are such a threat to aquatic environments. Take one to the desert, and plop down on hot sand, it'll be crispy by nightfall.

So...your question makes no real sense.

I disagree with you again, my Colorado blue spruce has gone through marshy and wet times for long periods of time without showing any signs of weakness.

Your example is no evidence of anything.....other than Colorado blue spruce are well suited for your Rocky mountain climate whereas birches are much less so. Unless with a source of water nearby. Blue spruces are known for their drought tolerance. Birches are known for their preference for even moisture. And it could well be that the birch succumbed to something other than drought....like BBB....but the issue was just exacerbated by dry conditions.

Location is everything - right plant, right place!! That's why we ask people their geographical location in addition to their zone.....because not every tree will do equally well - or not - in every location.

Perhaps you could frame your question around trees with naturally short lifespans. Trees with a super fast growth rate, with a genetically inferior infrastructure, or with a documented predisposition to a specific disease or pest, for example.

The weakest tree is probably some cultivar, developed by mankind for unnatural color, size, shape or other attributes, unable to survive on its own in any climate

Colorado blue spruce is extremely short lived in my climate, succumbing to rhizosphaera needle cast. Therefore it MUST be one of the weakest trees. ;-)

I can only speak by personal experience. I planted a Silver Maple in an area that had a good bit of moisture, a condition that it can thrive in, and, it reached about 6 feet, BUT, it basically fell apart. So, unless my neighbor did something to it, (it was close to the property line) or it was stricken with a disease. This neighbor had planted a row of them in the same area,so, I am NOT THINKING they were out to sabatoge MY trees, I just basically added to the line of S. Maples that THEY planted, BUT, my trees falling apart isn't normal, BUT, these trees basically (their limbs) fall apart in storms of mediocre strength anyway.

Callery Pear TREES have been said to be weak wooded also, and, they send seeds on the air and you end up getting seedlings that are very thorny, and can puncture car/truck tires if you drive through a place where the wild form seedlings have been growing. I have heard this mentioned here in the past about the Pear trees,so, I don't have personal experience with them myself. I'm just mentioning things people have posted in the past about the flowering Callery pear trees wild progeny.

Define 'weak'. Populus nigra Italica, commonly - Lombardy poplar, has to be close to the top. I have a weeping mulberry, the branches of which, when dead/dry, are easier to snap than a pretzel rod of the same thickness They weigh almost nothing when dry - lighter than balsa.

Al

Elm species that are susceptible to DED; American chestnuts. Neither will reach 'adulthood'.

It's a question a TROLL would ask, LOL