Lava does not destroy just wood itself. Platforms, most furniture, doors, etc. yeah. But I just ran a few buckets down some solid wood and there was no problem. Thank god they didn't make fire and flammability.
I was also thinking that perhaps just a little bit of lava coming above the pot would trigger the bloom, well, hoping.
And yeah, I think I can confirm that there's no requirements for Blinkroot to bloom, it's just random. I've seen them bloom/unbloom at all times of the day and night.
(Gold chests need to have more storage)