In my neighbourhood in Vancouver I used to have a monkey puzzle that produced both male and female cones and fertile seeds. I grew many little trees from the seeds. Last year I noticed that it has only female cones and no more seeds. This very puzzling and disappointing. Two friends also said they had found monoecious trees but when I went to look, sure enough, there were only cones of one sex. Is there an explanation for this that anyone knows?
I posted a couple of photos of monoecious monkey puzzles (in a thread of every large monkey puzzle I could find near Vancouver). In this posting: Three Vancouver Monkey Puzzle Trees I quoted Wikipedia's comment that these usually dioecious trees are occasionally monoecious or can change sex with time. So not an explanation - just, yes, they've been known to behave that way. There is a short discussion about seeds starting at posting #56 in that thread.
Here is an article about the Fortingall Yew in Perthshire, a tree of "international renown as potentially the oldest individual tree in Europe". I think it meant oldest individual yew tree. This male tree has put out some female cones, which was the point of the article from the RBG Edinburgh: Oldest yew tree switches sex. It doesn't offer an explanation either, but does say "many other conifers that have separate sexes, have been observed to switch sex."
I read it as saying it's the oldest tree there of any kind, which might be expected if it is actually 5,000 years old.
Yep - a bit off-topic on this thread, but the Fortingall Yew likely is the oldest tree of any in Europe. Unlikely that it is 5,000 years old though, best estimates I've seen put it in the 3,000 year range. It is of course hollow (well, a lot more than hollow, just some fragments of the original circumference!) so can't be dated accurately.
