Do dead plants leave behind dna?

Even if it was years ago and theres no visible plant? I ask because when I was a kid I saw a cactus that I really liked. I recently went to the location it use to be in to see if I could get a piece (stem). It was strange because the cactus was gone. It looked like it had never even existed. My question is....is if... show more Even if it was years ago and theres no visible plant? I ask because when I was a kid I saw a cactus that I really liked. I recently went to the location it use to be in to see if I could get a piece (stem). It was strange because the cactus was gone. It looked like it had never even existed. My question is....is if it died and rotted and turned to compost it must have left some dna that I could extract in a soil sample right?
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