Does Bocking Comfrey Ever Produce Seeds?

I have a couple Comfrey plants in my back yard (Bocking 4, one of the sterile hybrids).

I've had these plants several years and they have not moved.
Plus, there are a couple plants at my parents' place that have not moved for over 35 years. In fact, they are starting to look kind of anemic, not the strong plants they once were. Bottom line, they haven't spread by seed, so I am confident that they are, indeed, the sterile variety of Comfrey.

However, this afternoon when I was deadheading one of the plants in the back yard, I came across a seed. I thought I was looking at a Borage plant but, nope, it was Comfrey.

So now I am wondering, do the sterile varieties of Comfrey ever produce seeds? Perhaps the odds are extremely low--but not zero.

Alternately, if a sterile Comfrey plant is pollinated by common Comfrey, is there a greater chance that viable seeds will be produced?

Interesting find! I've got some wild varieties that probably are capable of self reproducing by seed. I doubt they'll go feral like the smaller kind, but maybe i should be a bit careful.
How do you know it's a Bocking variety? My friend passed me one which  ''of course it's Bocking 14''. He had found it by the roadside.. Never seeded though.
I multiply by digging the root up for balms, clones just appears in a crown after. They do need to be seperated ever4/5 years, they get kind of sad too long at the same place. Being great consumers of compost the ones doing best have gotten a spade of it at planting.

David Binner wrote:Perhaps the odds are extremely low--but not zero.

Biology is messy and loves to defy the rules we set down. I bet it's like that.

In my experience with hundreds of Bocking 4 plants, no.

My rosemaries sets seeds every year, thousands of them, only one time one sprouted, in an impossible crack in the pavement.
I love for plants to set viable seeds, because it makes them improvable to whatever nature throws at them, but comfrey seems one of those rare exemptions to that rule, it remains vital. It might change if more people start growing it and plagues get more experimentation space to play with and overcome the genetic codes.
Who was that Permaculturist having to move because his seed carrying creeping comfrey got carried all over by birds and the whole neighborhood got angry with them?  Or is he still full time fighting it?

Hugo Morvan wrote:
. . .
How do you know it's a Bocking variety?
. . .

I went looking specifically for Bocking 4.
I read that the roots of Bocking 4 go down ten feet and the roots of Bocking 14 go down eight feet. I wanted plants that go down as deep as possible because they were going to be planted along the sides of a creek and they were going to serve as erosion control, like living pilings that hold the ground in place.

The supplier I found said that he only ever had Bocking 4 on his property, nothing else.
Perhaps he lied.
Or he was being honest, but his supplier lied to him.
Or his supplier was being honest, but that supplier's supplier lied.
etc. etc.

Hopefully, everybody along the supply chain was honest.
Otherwise, there would be no way to confirm the genealogy of the plants all the way back to Bocking, England where the variety was developed.

All we can do is trust the people we deal with.