This is a common practice in many parts of the world/cultures. My buddy pulled a quick switch this spring because his daughters tree didn't make it through the winter. He timed it right and she just thought it got a slow start that spring! Its ok IMO all life comes from death with microbes doing the magic transition! Its just like planting a corn kernel in a fish carcass back in the day.
Instead of buying your kid a case of wine from the year of their birth, I was thinking the cannabis version would be like grow a dank plant with your childs placenta tea then make hash and save it for when you bust them toking. So this is "your hash"... and I only want you smoking the good stuff kid. Me personally I'd rather have that than a case of aged bordeau any day!
I still have my daughters (heart shaped, rare!) placenta in the freezer, maybe I will use it to make some tea on some plants like I said above. I did pump the water and afterbirth (home birth was great!) from the puddle birth (we were gonna do a water birth but she came when it was only 5" full!) right into my tomato bed and they are doing great this year even though they got seeded late by a new dad gardener who was about one and a half months behind schedule. MMmmm homegrown tomatoes, one thing I LOVE about late summer.
