The pot marks on the stems are from cankers. The advantageous roots growing under the dead bark in the cankered pockets is common on willows. No cure, maintain proper tree health. A properly planted tree unlike yours will have little or no issues.
Yep, notice no proper stump flare. Just a trunk that drops strait into the ground and perpendicular roots growing out at soil level. Also swelling of the lower trunk plus your canker health issues, all adds up to improperly planted from the start.
after we purchased the house a few years ago the willow tree's had mulch built up all around them. I cleared away alot of the mulch which is the only reason you can see any of the roots.
are the tree's planted to deep or to shallow? if the truck goes straight into the ground with no flare i would think they are planted to deep?