The pot of petunias are dead on impact
Oh, not again…
Hard to say. For a small plant with low water content, I could imagine that it would be effectively cryogenically preserved, meaning indefinitely. An aloe or other succulent, for example, would freeze and die. But maybe a stem cutting or woody plant might survive. Or a moss or lichen (though lichen aren’t plants). Assuming it doesn’t get baked by unfiltered sunlight or destroyed by high-energy radiation.
The best chance would probably be for some dry seeds.
It depends on the plant, moss apparently is pretty hardy. https://www.cell.com/iscience/fulltext/S2589-0042(25)02088-7
The water in the plant would immediately begin to boil (not because of heat, but because of the lack of air pressure in the vacuum of space), probably rupturing the cell walls of most cells I would think.
So to answer your question would probably be: The plant could continue to grow in space for a few fractions of a second.
