Didn't Noah send out the birds? And if the earth was completely flooded for 40 days, there wouldn't have been any ground based plants left alive. But you're a heretic, you don't believe the world was flooded.So all the species of cacti can survive floating in water for 40 days? Hmmm, don't think so.
Supposedly it rained for 40 days. It took awhile for the waters to recede.
I imagine most of the plants died but they grew from seed or from existing root structures. Moses sent out birds to look for land. One day one found plants and returned with a piece of one in his mouth. The last time he sent them out many didn't return, which means they found land and food.
I still believe there were isolated pockets that weren't touched by the flood. Nature took it from there.
Yes, I posted it.
Reading comprehension isn't your strong suit....
And the flood lasted longer than 40 days.