A seedling with three instead of two cotyledons, I don’t know if this is common or rare, but decided to post it anyway. It’s a Bonica x OP seedling.
Rob
Rob, it’s not uncommon. Sometimes these grow normally; sometimes they don’t. Anyway, don’t throw it away just because it has 3 cotyledons.
Peter
I wonder if you can send that photo to the ARS photo contests? They have areas for unique pics. I can almost imagine 2 people with their cooler and Coronas underneath that palm tree.
It isn’t common, but it happens. This year I had one with 4 cotyledons. It looked like a little four-leaf clover. I should have taken a picture of it. The seedling is alive, though not quite as vigorous as its siblings.
Jim, first you have twin seedlings, now you have 4 cotyledons - oh oh - maybe you should have your house tested for stray irradiation :>)
I have a picture of this somewhere in my computer from last year. The cross was Belle Isis X Renae. Looked like a 4 leaf clover with a smaller 5th one… strange.
I found it. It had 4 cotyledons. When the true leaves were coming out, it was strange. There was two very distinct types, one looking like damask/gallica and the other looking more smooth and modern. Could it be that this one was a cojoined twin if possible? This seedling didn’t survive, although a sister seedling did although it hasn’t bloomed at all.
Henry, I blame it on the flying saucers 
Jim maybe someone in your household needs anger management counseling :<)
Ha, I like the notion of the palm tree! Thanks for the info on multiple cotyledons, we’ll see what becomes of my seedling. Enrique, nice picture BTW!
Rob