How to Grow Your Own Tomatoes, Part 1: Starting Seeds Indoors
Growing tomatoes from seed isn’t hard, but there are a few things to be aware of.
If you peruse a seed catalog, especially one geared toward heirloom vegetables, you’ll quickly realize that the selection of tomato transplants in nurseries pales in comparison to the variety of seed that are available. Names like ‘Aunt Ruby’s German Green Tomato’ and ‘Missouri Pink Love Apple Tomato’ have been ascribed to varieties whose flavor and appearance are as eclectic and unexpected as their names imply. Growing from seed gives you the chance to experiment with some of these more unusual varieties.
Growing tomatoes from seed isn’t hard, but there are a few things to be aware of. As with all things agrarian, timing, genetics and environment have to be in alignment to reap the rewards of your efforts.
Time and Place
Tomato seeds are almost always started indoors – whether in a greenhouse or a sunny window ledge – and then transplanted to beds once they have at least a few leaves and an established root system. Starting seeds indoors is optional with many vegetables, but tomato seeds need a constant soil temperature of at least 60 degrees, and preferably 80 degrees, to germinate. In temperate climates, it may be midsummer before the soil gets that warm, and by then it’s too late for tomatoes to grow and mature before the end of the growing season.
Tomato seeds are typically started “six to eight weeks before the average date of last frost,” as the seed packets so ubiquitously state. Tomatoes originate deep in the tropics; temperatures below 32 degrees Fahrenheit are their death knell. And because they take three months or so to produce ripe fruit, most gardeners want to get the process started early.
So how do you know when your average date of last frost is? In the past, you might have consulted the Old Farmer’s Almanac. Today there are many websites that can tell you, including Modern Farmer’s own quick and handy frost chart. To give you an idea of the range: in Savannah, Georgia, it’s March 1; in Bozeman, Montana, it’s May 26. Find yours, subtract six to eight weeks and plant your tomato seeds.
Seed Sources
—
- High Mowing Organics
- Johnny’s Selected Seeds
- Rare Heirloom Seeds | Baker Creek Heirloom Seed Co
- Renee’s Garden
Process
‘Soilless’ potting mix (available at any garden center) is the medium of choice for sowing tomato seeds, though you can opt for the more expensive ‘seeding mix’ if you want. As for the container, cell packs (the tiny plastic pots grouped together in packs often used for flower and veggie seedlings) are OK for starting tomato seeds, but a better idea is to use a small pot at least 3 or 4 inches tall and wide so the seedlings can grow to a healthy size without their roots being constricted.
The three most important steps are:
- Fill the pots with potting mix to within a 1/2-inch of the top and place a pair of seeds on top of the soil in each one near the center of the pot (having two is good insurance in case one doesn’t sprout. Pinch off the smaller, weaker of the two if they both sprout).
- Cover them with a ¼-inch layer of soil mix and the compress the soil with your fingers. Good seed-to-soil contact is important for germination.
- Sprinkle water on the seeds whenever the top of the soil mix appears dry. Don’t keep the soil soggy, however – the seeds may rot.
The seeds will need a sunny window with at least 4 hours of direct sun each day, but preferably more. Also: the warmer it is, the faster tomato seeds will germinate. Maintaining room temperature above 60ºF will get the job done, but there are also seedling heat mats, heat lamps and many other tricks that farmers and gardeners have concocted to speed up the process. A simple approach is to cover the pots tightly with plastic and take advantage of the greenhouse effect to warm up the soil when the sun is out and hold on to the heat at night.
There is an important caveat about tomato seedlings and mini-greenhouses: If you’re covering your seeds to keep them warm, you must remove the cover as soon as they start to germinate. Otherwise, they may succumb to damping off disease, a fungal infection that proliferates in still, moist air. This appears as brown and grey spots on the leaves followed soon after by the death of the seedling). Damping off is a big challenge with tomato seedlings in general, so try to provide good air circulation during their infancy period indoors. A tiny fan or heat vent nearby is helpful, as is an open window from time to time (but only when outdoor temps get up to room temp).
Varieties
There are thousands of tomato varieties, but they all fall into a few broad categories. A single plant may produce scores of tomatoes over the course of the season, so you may want to strategize and plant one or two from each of the main categories.
Cherry tomatoes, such as Sun Gold, Napa Grape and Pear Drops, have the quintessential sweet-tart tomato flavor and are great for salads and snacking on whole. Because the fruit is small, these are the first to mature.
Sauce tomatoes, such as Roma, Amish Paste and Big Mama, have a richer flavor and much lower water content than other varieties. They’re the best ones for spaghetti sauce.
Beefsteak tomatoes, such as Mortgage Lifter, Cherokee Purple and Brandywine, have the biggest fruit and the greatest range of flavor and form. They are commonly sliced for sandwiches or making caprese salad, though the best varieties can be eaten like an apple.
There are also many all-purpose tomato varieties that have traits from each category. Most of the round, tennis ball size tomatoes at the supermarket would be classified as all-purpose. These are usually modern hybrids that rarely match the complex flavor – and diverse appearances – of heirloom tomatoes.
Finally, there is one often overlooked tomato trait that is quite important to be aware of. Somewhere on the seed packet in fine print you may find the words “determinate” or “indeterminate.” The former means the plant will grow to a certain, genetically determined size and then stop (the packet should indicate the size). The latter will grow indefinitely, as long as freezing temperatures or other acts of nature (or humans) don’t stop it.
Few people realize that in their tropical homeland, tomatoes are actually perennial vegetables, meaning they grow year after year, not for just one season. In the tropics (or here, in a greenhouse) indeterminate tomatoes eventually become vines more than 20 feet long. The practical ramifications for North American growers are that indeterminate tomatoes need much more space – they can easily grow 6 or 8 feet in a six-month growing season before succumbing to frost. If you want a compact tomato plant that fits inside a standard 3- or 4-foot tomato cage, go with a determinate variety. You will get more tomatoes overall with an indeterminate variety, but determinate varieties typically yield more fruit per square foot.
Tomato Woo-Woo
Planting tomatoes according to the local date of last frost is a no-brainer. But if you want to get metaphysical about it, consider the position of the moon and stars. Biodynamic growers are highly attuned to cosmic influences in agriculture and plant according to a yearly calendar based on celestial events.
Farmer’s almanacs have traditionally been based on the same phenomenon. For example, the current Farmer’s Almanac says that March 24 and 25, 2015, are terrible times for planting any seeds, but recommends April 3 for tomato planting in particular.
Join us again in early May for part two of the series, where we’ll lay out the finer points of “hardening off” the seedlings, preparing the soil and providing your sensitive seedlings with just the right juju to grow lavishly and fruitfully through the summer.
Follow us
Republish!
Republish our articles for free, online or in print, under a Creative Commons license.
Republish this article
This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.
Want to republish a Modern Farmer story?
We are happy for Modern Farmer stories to be shared, and encourage you to republish our articles for your audience. When doing so, we ask that you follow these guidelines:
Please credit us and our writers
For the author byline, please use “Author Name, Modern Farmer.” At the top of our stories, if on the web, please include this text and link: “This story was originally published by Modern Farmer.”
Please make sure to include a link back to either our home page or the article URL.
At the bottom of the story, please include the following text:
“Modern Farmer is a nonprofit initiative dedicated to raising awareness and catalyzing action at the intersection of food, agriculture, and society. Read more at <link>Modern Farmer</link>.”
Use our widget
We’d like to be able to track our stories, so we ask that if you republish our content, you do so using our widget (located on the left hand side of the article). The HTML code has a built-in tracker that tells us the data and domain where the story was published, as well as view counts.
Check the image requirements
It’s your responsibility to confirm you're licensed to republish images in our articles. Some images, such as those from commercial providers, don't allow their images to be republished without permission or payment. Copyright terms are generally listed in the image caption and attribution. You are welcome to omit our images or substitute with your own. Charts and interactive graphics follow the same rules.
Don’t change too much. Or, ask us first.
Articles must be republished in their entirety. It’s okay to change references to time (“today” to “yesterday”) or location (“Iowa City, IA” to “here”). But please keep everything else the same.
If you feel strongly that a more material edit needs to be made, get in touch with us at [email protected]. We’re happy to discuss it with the original author, but we must have prior approval for changes before publication.
Special cases
-
Extracts. You may run the first few lines or paragraphs of the article and then say: “Read the full article at Modern Farmer” with a link back to the original article.
-
Quotes. You may quote authors provided you include a link back to the article URL.
-
Translations. These require writer approval. To inquire about translation of a Modern Farmer article, contact us at [email protected]
-
Signed consent / copyright release forms. These are not required, provided you are following these guidelines.
-
Print. Articles can be republished in print under these same rules, with the exception that you do not need to include the links.
Tag us
When sharing the story on social media, please tag us using the following: - Twitter (@ModFarm) - Facebook (@ModernFarmerMedia) - Instagram (@modfarm)
Use our content respectfully
Modern Farmer is a nonprofit and as such we share our content for free and in good faith in order to reach new audiences. Respectfully,
-
No selling ads against our stories. It’s okay to put our stories on pages with ads.
-
Don’t republish our material wholesale, or automatically; you need to select stories to be republished individually.
-
You have no rights to sell, license, syndicate, or otherwise represent yourself as the authorized owner of our material to any third parties. This means that you cannot actively publish or submit our work for syndication to third party platforms or apps like Apple News or Google News. We understand that publishers cannot fully control when certain third parties automatically summarize or crawl content from publishers’ own sites.
Keep in touch
We want to hear from you if you love Modern Farmer content, have a collaboration idea, or anything else to share. As a nonprofit outlet, we work in service of our community and are always open to comments, feedback, and ideas. Contact us at [email protected].How to Grow Your Own Tomatoes, Part 1: Starting Seeds Indoors
by Brian Barth, Modern Farmer
March 12, 2015
Modern Farmer Weekly
Solutions Hub
Innovations, ideas and inspiration. Actionable solutions for a resilient food system.
ExploreExplore other topics
Share With Us
We want to hear from Modern Farmer readers who have thoughtful commentary, actionable solutions, or helpful ideas to share.
Submit
Am a student who is interrested in all branches of knowledge.i practice olericulture were i planted tomantoes and onions in small scale (in a land of about 60m by 40m)but i managed to get 9million ugandans shillings
I love heirloom varieties because almost all of them boast greater flavor than that found in hybrids
I’d love to receive your catalog. Can it be sent electronically?
Where is the next part?
I would like a catalog could you pleas send ne one free
How do I get one of your catalogs?
I would like a a catalog
I have “USA” Lucid Gem Tomato seeds and want to know how to plant them … can you give me any tips? Thanks
?
Should I add coffee grounds or egg shells to the soil when I plant my tomato seeds?
Grow your tomatoes indoors and follow the instructions in this article. It’s easy to understand and will give you ideas on when is the best time to plant tomatoes. Informative article.