Last Updated: September 29, 2023

Vegetable Garden Trials: Carbon Black Heirloom Tomatoes

By Published On: August 30th, 20234.7 min readCategories: Garden, Plants

Last Updated: September 29, 2023

In our home garden, this year’s surprise performer is Carbon Black, a mid-sized heirloom tomato that produces heavy loads of 8 – 16-ounce fruit

Annual Vegetable Garden Tomato Picks

Now that we’re two-thirds of the way through the growing season, it’s a good time to take stock of what’s done well in this year’s garden so we have time to save some seed from the best producers for next year’s garden.

We love tomatoes, so they’re always a big chunk of the bed space. Beefsteak, Brandywine, black, red, pink, grape, cherry, pear, you name it, it’s probably growing here.

The little ones are for snacking and salads, some of the others are for cooking fresh, but most are grown for saucing and canning so we can enjoy the fruits of our yard through winter and into early spring.

Not surprisingly, we go heavy on the types that are meaty, dense, and in the 4-to-12-ounce range. We also prefer to stick with open pollinated heirloom varieties because the results are more consistent over the generations than hybrids are.

a bowl of ripe garden tomatoes

A few Carbon Black Heirloom tomatoes picked fresh this morning

This year’s selection included Oxheart (2020 seed), Pink Brandywine (2021 seed), Costaluto (2021 seed), and Carbon Black (2018 seed).

They’re all indeterminate, so they’re still producing, but the yields on the Oxheart have been lower than expected, the Brandywines have had trouble with cracking and mice, and the Costalutos are taking their sweet time with the first fruit harvested 90 days after planting.

The one bright spot has been with Carbon, a black tomato that’s reasonably quick to mature (70-75 days versus 80 plus for the others) and produces 8-to-16-ounce fruit with a deep pink/purple skin and green-streaked shoulders.

A hand holding a large red tomato

This carbon tomato weighs 1-1/2 lbs!

To be honest, were you to ask me back in March which of the big tomatoes would be the stand out this year, Carbon would have been my last guess. The seed was 4-1/2 years-old when I planted it, so I wasn’t expecting much and planted it more as a novelty.

But, lo and behold, six pots were seeded and six pots germinated. In April they filled a whole bed section by themselves and never looked back.

What makes carbon tomatoes stand out

  • Old heirloom the seed keeps well and breeds true year after year
  • Large, dense fruit with a small seed wall and rich tomato flavor fresh or cooked
  • Harvests start 2 – 3 weeks earlier than other large varieties
  • Produces over a long period – 8 weeks or more
  • Each plant can produce 20 pounds of tomatoes
  • Smooth shape and easy to separate blossom end makes it easy to peel the skin from the fruit when canning

Carbon tomato drawbacks

  • Cracks and scars easily in humid and/or wet conditions, so they’re not always pretty

    It’s not always the most attractive tomato

  • Big plants take up a lot of room and need strong support
  • Fruit falls easily, especially in windy or rainy conditions
  • Every pest under the sun – insects, rodents, birds, etc. — loves them, so be prepared to protect them

Observations and conclusion

While a surprise addition to the 2023 vegetable garden lineup, the Carbon Black tomato’s results have been outstanding.

At the moment of this writing, we’ve harvested somewhere on the order of 80 pounds of tomatoes since the end of July, and are probably looking at an additional 40-50 pounds before they’re played out for the season.

Water content is low compared to beefsteaks and slicers, and the flavor is second to none – smoky and rich, not sweet or acidic – so it’s perfect for both slicing fresh and canning / saucing.

Like most of the other tomatoes, the cool spring and early summer did delay fruit production, but I noticed a huge uptick in output after Hurricane Tropical Storm Hilary blew through earlier this month. It may be that this tomato likes hot, humid, and wet conditions (unusual for us here in San Diego), which is why I haven’t paid much notice to it in the past.

Unfortunately, those same conditions also cause the tomatoes to spider, crack and split, so they’re not always the most attractive tomatoes.

Additionally, it seems every pest under the sun, from aphids and tomato worm, to field mice and mockingbirds love the taste of the Carbon tomato. They’re easy enough to control with stuff like BT, bird deterrents, and rodent spray, but you have to be on your game from the time the fruit first appears on the flower until final harvest.

All-in-all, Carbon Black heirloom tomatoes are a real star. I definitely recommend trying them out in your garden. They’re definitely going to become a permanent resident in mine.

Carbon Black tomato specs

Plant Details
Size Large plant – 6-ft to 7-ft tall, 4-ft spread

A tomato plant in a vegetable garden

Carbon tomatoes are big plants. Over 7 feet high and 4 feet across!

Growth habit Indeterminate
  • Produces abundant fruit in clusters of four (but only two or three will reach maturity)
  • Mature fruit is 3-1/2-in. to 6-in. across and weighs between 8 and 16 ounces. (One of mine weighed in at 24 ounces)
  • Each plant will produce between 15 and 20 pounds of tomatoes
  • Great flavor fresh, cooked and canned or sauced
Sage’s Rating ★ ★ ★ ★ ☆
(4 out of 5 stars)

Video: Carbon Black Tomato

Everything you need to know in under 2 minutes.

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  1. Peggy Lawver September 20, 2023 at 3:42 pm - Reply

    Looking for an acid tomato for canning, and what is a good salsa tomato.Thanks

    • Sage Osterfeld September 22, 2023 at 9:37 am - Reply

      My go to tomato for canning is Bonny Best, an heirloom variety indeterminate. The plants produce over a long period (I have some that started fruiting back in June and are still going today), and the skins slide right off when you’re processing them.

      As for salsa, any good, meaty paste tomato will do. Here in San Diego where salsa is more popular than ketchup the preferred tomato is the Roma. They’re easy to grow, impervious to most diseases, and have a nice meaty fruit that won’t get watery and mushy in the salsa.

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About the Author

author avatar
Sage Osterfeld
I’m just a guy with nearly an acre of dirt, a nice little mid-century ranch house and a near-perfect climate. But in my mind I’m a landscaper survivalist craftsman chef naturalist with a barbeque the size of a VW and my own cable TV show. I like to write about the stuff I build, grow and see here at Sage's Acre.

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