How to Grow Tomatoes From Seed
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Tomatoes are a staple in just about every home vegetable garden. They can be grown in garden rows, raised beds or containers, in greenhouses, on acres of land or on balconies. And there are sooo many kinds to choose from.
If you’re looking for a good canning or sauce-making variety, choose a paste tomato like Amish Paste or San Marzano. If you want a snacking variety, choose a cherry or grape variety. If you want a big, juicy slicing tomato, opt for a Beefsteak. And if you just want fabulous fresh-eating tomatoes or unique colours and patterns, choose any of the thousands of diverse varieties of heirloom tomatoes that exist around the world.
I guarantee the first time you grow tomatoes from seed will not be your last. Much like chickens are the “gateway animal” to the barnyard, tomatoes are the “gateway vegetable” (okay, fruit) to the home garden.
We’ve been growing tomatoes in our garden every year since, well, since we started gardening. And technically, even before that! I used to grow tomatoes on my patio years ago when I lived in the city. I certainly would NOT have considered myself a gardener at the time, but I did have a few herbs and potted tomato plants on my little ground-floor patio, and it made me feel pretty proud (and a little like I was cheating the system) to be able to snip a few herbs or pluck a few tomatoes right from my own patio. Very cool for a born and raised city girl!
But back then I didn’t grow anything from seed. I bought tomato seedlings from our local garden store and watered them. That was about it.
They did okay for a while, but slowly the leaves began to curl, the new blossoms began to drop off and some tomatoes developed black spots on the blossom end (yes, I now know this was blossom end rot).
I got a few fresh tomatoes that year and was over-the-moon about it, but I really had no idea what I was doing when it came to growing and caring for tomatoes. In fact, at the end of the season as I was packing up my life to move overseas for a year, a friend of mine asked if he could take my tomato plants, which still had a few fruits clinging to the vine. He said he wanted to plant the entire tomatoes and let the seeds grow into new plants. I was completely floored that this was even possible. Imagine that! Me, Little Miss Homesteader, had NO IDEA you could regrow tomatoes from the seeds that were inside. Crazy, eh?
But roughy a decade later, now I know. And I’ve been working on my tomato game for the past three years.
Aside from broccoli, tomatoes are the one
vegetable fruit we’ve grown consistently year after year. And while we’re no experts after our three, going on four years of experience, we’ve had enough successes (and failures) growing tomatoes that I think it’s high time I start passing on the knowledge and lessons we’ve learned, so that even if you’re a total tomato newbie, you too can grow baskets full of tomatoes this year for fresh-eating all summer long (and even more to preserve for next winter).
Let’s get started…
How to Start Tomato Seeds Indoors
- Start tomato seeds indoors 6 to 8 weeks before your last frost date.
- Sow seeds ¼ inch deep and cover with soil. Keep watered (but not soaking).
- Once tomatoes are roughly three inches tall and have a couple sets of true leaves, transplant them to larger pots to give their roots room to grow.
Tomatoes love warmth, and tomato seeds are no different. Seeds germinate best in warm soil that’s preferably somewhere between 75ºF and 85ºF (23ºC to 29ºC). For this reason, you should start tomatoes indoors roughly 6 to 8 weeks before your last frost date as seeds will not germinate if you direct sow them outside (or even in a greenhouse) too early in the season when temperatures are still too low.
You can plant seeds in just about anything (containers, egg cartons… eggshells!) but I like using peat pots. They’re easy to use, cheap to buy, have adequate growing space for seedlings to grow strong roots, they drain well and they can be planted directly into your garden without having to mess around with trying to get the seedling out of the pot and into the soil. But hey, the choice is yours;)
You can plant two or three seeds per pot to ensure good germination rates and then thin them out when they start to grow, or just plant one seed per pot. In my experience tomato seeds have a pretty good germination rate so I usually just plant one or maybe two per pot.
Plant tomato seeds ¼-inch deep and cover with soil. Water regularly to keep soil moist while seeds are germinating.
Seedlings will need a place to grow indoors that is consistently warm and has adequate light. You can purchase your own set of indoor growing lights or make your own. You can also keep seedlings near a sunny window, but beware that keeping them near a window in cold weather could stunt their germination and growth if there’s a draft. Plus, plants will grow toward the window instead of straight up toward the grow lights, so if you can use indoor growing lights, I recommend doing so to start your tomato seedlings.
Keep in mind that seeds do not need light to germinate, just warmth. Once they sprout, however, the seedlings themselves will need light to keep growing.
You’ll also want to make sure you have adequate space where you will have room to transplant your baby tomato seedlings into larger pots to help their roots to keep growing before transplanting them outdoors.
Transplanting Tomato Seedlings Outdoors
- Transplant seedlings outdoors when all chance of frost has passed and nighttime temperatures stay consistently above 50ºF (10ºC).
- Tomato seedlings should be hardened off for about 7-10 days to get them used to the outdoor temperatures.
- To transplant, dig a hole that is a few inches deeper than the height of the pot that the tomatoes are in. Plant tomatoes deep enough that the soil reaches the first set of leaves at the bottom of the plant.
- For best results, fertilize/add calcium to the soil before planting.
Make sure to wait until outdoor temperatures are consistently warm enough before transplanting tomato seedlings into your garden. Nighttime temperatures should not drop below 50ºF (10ºC). If you have a greenhouse you might be able to transplant them outside a few days or even a couple weeks earlier if temperatures inside the greenhouse stay consistently warm enough.
Tomato seedlings will also need to be hardened off before transplanting permanently outdoors. Hardening off simply means you get the seedlings used to being outside slowly instead of just putting them outside and leaving them there. After a sheltered, warm “upbringing” indoors, this violent shove into the outdoor garden can shock the plants and even kill them. So be gentle. Go slowly.
To harden them off, bring potted tomato seedlings outside for a few hours the first day and then bring them back in. Put them outside for about an hour longer every day and then leave them outside overnight on about day 5 or 6 (while they’re still in their indoor pots). Transplant into the ground or into their permanent spots by day 7 to 10.
When planting, dig a hole that is deep enough that the soil will reach the first (bottom) set of leaves, then prune the bottom set(s) of leaves so that no leaves are touching the soil. This encourages a strong root system which makes for stronger, healthier plants and helps ensure tomatoes leaves stay dry which helps to prevent blight and other common diseases.
For optimal results, sprinkle in some fertilizer and/or add some finely crushed eggshells to the soil. The calcium in the eggshells helps to prevent common problems like blossom drop and blossom end rot.
Work the fertilizer/eggshells into the soil, place a tomato plant in each hole (up to its bottom leaves) and fill with soil. Give plants a deep watering.
Caring for Tomato Plants
- Grow tomatoes in a warm, dry, sunny location. Tomatoes do especially well in greenhouses and under high tunnels if you have them. Otherwise choose a warm, sunny location outdoors.
- Tomatoes should be planted in well-drained areas as soggy soil can rot a tomato plant’s roots.
- Water tomato plants at the base of the plant so that the leaves stay dry. Water deep every two or three days.
- Indeterminate (vining) tomatoes will need to be staked or caged to help them stand up straight. Here are the stakes that we use and recommend.
- To prune tomatoes, remove any damaged, yellowed or diseased leaves and any leaves at the bottom of the plant that are touching the soil. Pinch off suckers on indeterminate plants.
- Harvest tomatoes when they turn red (or ripen to the colour they’re meant to be!)
Tomatoes originated in South and Central America, so naturally they love the sun and the heat. Plant them in a warm, sunny location in your garden or in a greenhouse.
Tomatoes also like to be kept dry, so make sure to plant them in an area that is not likely to get too much rain (put them under a high tunnel or an awning on a balcony to keep them dry if you live in a really rainy area) and water close to the base of the plants in order to keep the leaves dry. Wet leaves invite fungus and diseases like blight.
Make sure tomatoes are planted in well-drained areas. If you plant them in pots, make sure there are enough holes in the bottom of your pot/planter to allow water to drain. We’ve grown our tomatoes in 5-gallon buckets for the past couple years and punched around 10 drainage holes in the bottom of each bucket. This has worked well for us.
Soak tomato plants once every 2 or 3 days (depending on how hot and dry it is). Tomato plants respond best to a deep watering every few days rather than light watering every day.
Make sure you know whether your tomato plants are determinate or indeterminate. Determinate simply means that they will grow to a pre-DETERMINED height and then stop growing. Indeterminate plants are vining plants that will keep growing. They need to be caged or staked, and they also need more pruning than determinate varieties.
When it comes to keeping them upright, I much prefer to stake them than to cage them as I find our plants fill out the tomato cages really quickly and it’s harder to prune and even get at some of the fruit, but whatever works best for you is just fine. We started using these spiral tomato stakes with out tomato plants a couple years ago and they’re fantastic and easy to use and adjust as the plants grow taller. I don’t think we’ll ever use anything else.
Prune all varieties by snipping off any yellowed, damaged or diseased-looking leaves at the base of the branch that they’re on. Discard and destroy these leaves and branches in the garbage or fire pit. Do not add diseased leaves to your compost pile as they can infect your compost and damage other plants.
Also, prune any lower leaves that are touching the soil. These leaves are more susceptible to moisture from the soil and can be a conduit for blight.
When it comes to indeterminate plants, you’ll also want to prune off the suckers. Suckers are new vines or side shoots that grow out of the “crotch” between the stem and a branch. If left un-pruned, these suckers will grow into brand new vines. While they will produce more blossoms that may eventually fruit, if you let all the suckers grow then your tomato plant will use all of its energy to produce more suckers and leaves instead of producing fruit.
Best practice is to prune most of the suckers, but leave a few (maybe two or three) closer to the middle of the plant so that you get a couple new vines and some more fruit. Otherwise try to be diligent about pruning suckers while they’re still small.
Finally, harvest tomatoes when the entire fruit has turned bright red (or whatever colour they’re meant to be when fully ripe). Indeterminate plants will usually continue to grow and produce fruit until it gets too cold, so if you end up with unripened green tomatoes that you know won’t have time to ripen in the fall, you can still put them to use. Maybe make some fried green tomatoes or a batch of green tomato salsa!
However you slice ’em, tomatoes deserve a place in your garden this year. So, whaddya say? Will you be growing some from seed? Let me know, down below 🙂
Oh, and don’t forget to grab your FREE Seed Starting Cheat Sheet. It includes at-a-glance info on exactly when and how to start 10 common garden vegetables from seed (and yes, tomatoes are on the list!)
Wishing you health, wealth and baskets full of delicious homegrown food:)