If you want dwarfs, you should definitely save the seeds and plant as many seeds as you can. You could plant 30 or more in one container. With any luck, as they start to grow, you might find that some of the seedlings are shorter than the rest, so select those for your project and discard the rest. It sounds like a fun project!

Do you know the name of the variety that you are growing?

Linda

First, you will need to confirm that the plant in question was truly what is considered 'dwarf'.

You said that the variety usually grows 7'+ tall. I've had determinates reach that height. Is the variety determinate, or indeterminate?

Instead of the plant showing dwarf-type traits, how sure are you that the smaller stature wasn't environmental instead of genetic? It's always possible the plant was stunted by unknowns in the growing conditions.

If the plant indeed 'mutated', or perhaps expressed some sort of regressive genetic dwarf traits, then as Linda posted above, you'll need to grow out as many seedlings as you can and 'select' for your preferred characteristics.

If your goal is to isolate the dwarf style while keeping all the other positive aspects of the variety, the only way to really do it properly is to grow the plants separate from any other tomatoes, including taller plants of that same variety. You'll want NO potential cross contamination at all. The smallest introduction of unwanted pollen could ruin a lot of time and work.

Short of a climate-controlled greenhouse, I'd think about doing it in a tunnel. Make the tunnel high enough to only fit a 'dwarf'. 5' should suffice. Pinch back all flowers until your plants express the dwarf trait - cull any plant that hits the top of the tunnel. You could leave the flowers and harvest early fruit to test for taste characteristics, but if the variety you have is as stable as you suggest, then unless the flavor genes are associated with the dwarf characteristics you shouldn't have to worry too much about that problem.

To breed a strong line, consider finding at least 2 plants of the same variety that express the trait and cross them. Even though tomatoes are a fairly stable, self-pollinating species, avoiding in-breeding one plant into a new variety will help future success. By crossing at least 2 plants showing the same trait, and back-crossing with as many you can find in the future, you may indeed establish a new stable dwarf expression of the variety bred to succeed in your region.

You might even consider cloning. If the plant is still alive now, take a clipping and root it indoors. Keep it alive under lights all winter. Take more clippings in the spring and plant them outside. If the clippings keep the dwarf trait you'll have a better idea of the potential. You can then use those clones in your trials. Just remember that with breeding, clones should be considered one plant. Crossing 2 clones from the same mother plant is still in-breeding.

The one that grew dwarf could be due to the environment factors. For example, planting some determinant ( even some indets) in a small container can make it grow like a dwarf. That is a Bonsai effect in limiting the root space/size.

Mutation is another possibility. In this case if you plant seeds from it, then it should grow as dwarf. JMO

You don't need to totally isolate your plants. If you want to be sure the seeds are not crossed, you could bag blossoms.

Many, many thanks for the very useful advice posted above. Yes, I do know the name of this non-hybrid, indeterminate tomato under discussion. I have followed the GW tomato forum since the early days and have seldom seen it mentioned.

No, the dwarfing of this tomato was not due to cultural differences. I have been rooting cuttings of it all summer and it is still showing dwarf tendencies. Rooted cuttings will be saved this winter and next spring I will try all the above suggestions.

This is what's fun about the world of horticulture. Endless adventures to explore. One eye always open for the unusual.

I grew a determined dwarf German heirloom variety called Rotkäppchen. It grows to about 2.5ft tall. You can read my Amazon review on it with some photos.

Good review!

Linda