Those pictures were from last week, so here are some new ones from this morning.

What you experienced is fairly common with many heirloom tomato varieties only. I confront the problem regularly when limiting plants to one stem. The “Forked” branches cannot be snapped off by hand and thus one branch must be pruned. The plants otherwise are not adversely affected. I usually take the pruning event as an opportunity to remove fused blossoms simply because the resulting fruits have low marketability percentage. You can strive for a record weight fruit if you leave those on the plant.

Over years of plant growing I have noted that some varieties are more subject to fasciation than others. Why? What is causing it? Slowly, through observation of climate conditions and daily walks among my plantings an inkling of a thought. Could ozone fall out possibly be the cause of plant fasciation? I now believe that it is. For those with a scientific curiosity there are online directions for testing ozone fall out. There are certain mornings when you can 'feel' the air and sense ozone fall out. Some of you will understand what I am trying to describe.

Thanks for the responses. I grow almost exclusively heirlooms, but I don't generally grow beefsteak type tomatoes and it seems to me from a little reading that they may more commonly be affected. Does your experience seem to support that? I don't think the extra sturdy stem seems to be causing any harm, so I am looking forward to seeing how the plants and fruit compare to our Cherokee Purple from last year.

I've had this happen before. I never really paid attention to if heirlooms or beefsteaks do it more, just some plants have had it, some have not. I do tend to grow a lot more smaller tomatoes than beefsteaks in general, and more heirlooms than not. I just always assumed sometimes it happens, like sometimes fused flowers make those great double fruits.

I've always taken it as a sign of vigor. However, if it means more fused blossoms, I can see how someone who likes uniform fruit shape and size might not prefer it.

I got a number of plants like this, this year, but hardly any in past years.