Well I have never made ketchup but I make sauces, like spaghetti sauce. If you simmer SS longer to reduce it , get it thicker, you will end up with some kind of paste, from which you can make ketchup.

Basically, for making ketchup you'll need the so-called "paste" tomato varieties that have less water, more meat. Tomatoes in Roma, SanMarzano and a lot of heart varieties are better suited for making paste, if that is what you want.

Wait for more expert recommendations, plse.

So your real issues are finding a red OP that is a small plant and will do well "in cool, often wet summers, in zone 4B".

Generally "small plants" equals determinate varieties rather than indeterminates so that eliminates many of the best paste types and the hearts. Consider improving your growing conditions if possible to increase your options for the bigger plants.

Do you buy plants or grow your own from seed? Growing from seed will improve your choices substantially.

Otherwise most any of the determinate, red variety OP's that are available for sale locally will work well.

Dave

To answer your question digdirt, so far I have been buying my plants. Part of the reason I posted this question is because I want to start my own plants from seed next year, and start saving my seeds. I think you might be on to something when you suggest determinate varieties. Can you (or someone else) suggest some OP red determinate varieties with exceptional flavour that I can blend, and can tolerate cool, often wet, summers? I don't mind doing mail order.

Dave

Costoluto Genovese - highly productive indeterminate intense flavored red tomato with fluted shoulders.

Heidi - determinate paste type, highly productive, adaptable to many climates.

Rio Grande - Paste type with high production and rich flavor.

The problem with the above is that they are relatively low in sweetness. If you insist on sweeter ketchup, you will have to either add sugar or grow a sweeter variety like Crnkovic Yugoslavian to blend in the mix.

My concern was the need for varieties that were NOT indeterminates since so many great ones are,

For paste varieties two that I can highly suggest are Heidi and Martino's Roma, the former semi-det and the latter determinate.

Those can be used to thicken up whatever else you might use.

Off hand I can't think of any meaty, low seed beefsteak varieties, great tasting, etc, that are determinates,

As to hearts the one determinate I love and should meet all your needs is Danko, a red heart.

I gardened in a 4b/5a area , same as you,

Carolyn

I admit, have bad palate and weak nose too. hehe

Since tomato is so adulterated in ketchup, it is boiled, salted and heavily condimented ... I wouldn't be concerned about any fancy heirloom and just go for a good acid-balanced producer of old fashioned tomatoes that Campbell's would be proud of, not too way south from your zone, and it will probably taste best.

My first choice is actually the OP Marglobe, a basically determinate, stout and vigorous plant. Rutgers (OP) is actually a cross between Marglobe and a Campbell's tomato and Marglobe has old fashioned appeal to me - probably the ketchup my grandparents had as kids. The plants are easy to grow and produce very well, and the disease resistance will be great as a starter.

I have grown both Rutgers and Marglobe and they were more fun than my other OPs, except Cherokee Purple which I'm always amazed by (but would prefer Marglobe for ketchup & its production).

Best growing.

Since I first posted someone has given me some Pantano Romanesco seeds as a gift. I had never heard of them but their description sounds delicious. Unless someone tells me they likely won't do well in my climate, I will use them as the base, and layer on one or two other varieties. Cheers everyone!

Always something else to think about and it never ends when deciding which varieties to grow,

Carolyn

Dave