call your nursery about planting times
I live in the desert (Utah) and trees actually grow best when planted in the fall here. We planted a tree on my placenta last May and it died

from the heat. But we took it out and planted another tree in November, I think, and it's grown 3-4" (pretty good for a pine). And it had a chance to get its roots deep enough to survive the long hot summers we have here. So if I were you, I'd call your local nursery and ask them when the best time to plant a tree would be-it really varies by region.
Also, you can freeze your placenta until then, or you can plant the placenta (deep enough it won't attract animals) and let it decompose a bit before planting a tree, and then plant the tree when it's ready. Means you have to dig the whole twice, but some dads are happy to do that in exchange for not having placenta in their freezer

And, to add to the list of things you can do with a placenta, I've heard of drying, grinding it up and capsuling it to take daily, if you're not sure about eating it with a knife and fork but still want the nutrition. Never tried it, but it's another idea.
Happy Birthing to you and your family!