A Gardeners Forum Forums General Discussion The Plants and Flowers Forum Mystery Plants? Mystery tree seedlings

After 30+ years an area of property was dug and the soil turned, and now we have dozens of these tree seedlings popping up, but I am unsure of what species. I had though black locust which is nowhere near my area, but from googling black locust seedlings sprout 2 round true leaves on thin branches, these never got those, so perhaps honey locust? The leaves fold at night.

Look up mimosa, Albizia julibrissin. That is what it looks like to me and they behave by closing at night. I love mine but I do need to take out volunteers. And the birds will spread those volunteers quite a distance from mamma tree.

I looked and it does look very similar, but reading about it said the mimosa leaves will shut when touched, these dont shut when I touch them. Not sure if seedlings mabye dont do it or this is NOT a Mimosa.

Some mimosas close when touched. Mine do not.

How do I tell the difference between mimosa and black locust, as both of these trees are in my area, the seedlings look so similar. Any other way to see the difference?

I used to grow sensitive plant seeds, as the plants were great fun for the kids. When one touches the leaves, they fold up. They are in the mimosa family, and your seedlings look just like the plants that grew from the seeds.

Black locust have leaves: Parallel, compound, odd-pinnate.
Meaning the leaflets are not right across from each other but staggered up the stem.
Mimosas have the leaflets directly across from each other. Yours is a mimosa.
Black locusts will eventually develop a thorn, mimosas don't. And then there is the flower type and color eventually.

Well that's great news, but it makes another mystery. Our neighbor and my family have lived here for over 23 years, none of ever had Mimosa. Yet when he recently got a fence put in on the border between our two yards and turned the soil, we suddenly had all the sprouts all over. So does that means these sprouts are from seeds over 23 years old, and at one time a mimosa was on one of our properties?

Maybe. I'd still go with birds dropping them on you, though. And they are taking advantage of the loosened soil.
My birds around here eat the berries from poison oak and then deposit gifts in my gardens. I have to diligently weed.