Growing Tomatoes Part 1: Seeding & Transplanting Seedlings

 How & When to plant tomato seed, picture guide, transplanting


Growing Tomato Plants from Seed

Growing plants from seed can be a very rewarding and fun experience when you start with just a few, basic know-how’s. I have seeded everything from broccoli, peppers, and watermelon to beans and much more, and of course, lots of tomatoes. In this post I will use pictures to show you what to do to plant tomato seeds, how to care for the tiny seedlings, and also how to transplant them when the time is right.

The first time I seeded anything at all, more than a decade ago, was a complete flop. Since then, I have learned just how easy it can be, and have grown to really love seeding my own plants. My absolute biggest mistake in the very beginning was to put the newly seeded trays away from where I could see them in order to also keep them away from my cute little toddlers. The problem was that since I didn’t see them, I forgot about them (the trays, not my toddlers! Ha!) and didn’t water the seedlings often enough. When I did water, I didn’t realize just how fragile these tiny plants were, and knocked them over while watering from a watering can that was far too forceful for them. The poor little plants didn’t stand a chance and quickly gave up. And so did I. I did not believe I had it in me to grow anything from seed!

It took years before I decided to try again, this time to find that I do, indeed, have it in me! And most likely, so do you! Now that I keep my sprouting little seedlings where I see them daily, and tend to them carefully, I have grown countless tomato sprouts into huge, beautiful, lush plants, many of which were transplanted into my own garden, and still more that I have had the pleasure of sharing with others.


Selecting Seeds

What type of tomato you will want, and how large the tomatoes should be, will of course be one of the first things to think about. However, there are some other things to keep in mind as well when selecting seeds:

Plant Size:
Some plants are determinate, others are indeterminate. Indeterminate plants will continue to grow and produce fruit all season long until the plants die from hard frost in the fall. If they are in ground and conditions are right, some will grow to be 8 feet tall or more, requiring heavy staking. A grape tomato plant that I gave to my father-in-law grew high up into a nearby tree! When in pots though, they will not necessarily grow much beyond 4-5 feet. Sometimes determinate plants will be more manageable as they grow to a certain size and will stay this way. They usually do not require staking as they will be more compact, perfect for a patio. However, they will grow only one crop of tomatoes that will all ripen at about the same time. I have grown both determinate and indeterminate plants on my deck and in ground without a problem. I would not let size be the determining factor when choosing seeds or plants unless space was a true problem.

Hybrid vs. Heirloom:
Most tomato plants and seeds available at stores and nurseries these days (as well as supermarket tomatoes) are hybrid varieties, which means they have been specially grown and bred to create disease resistant and hardy plants and fruit. Flavor is often sacrificed, though there is still no comparison between a homegrown tomato and one from the store! Fruit that has been allowed to slowly ripen on the vine is so much worth the effort it takes in caring for the plants.

Heirloom tomatoes, which have been reproduced for several generations, are often more flavorful, but these plants are prone to disease and harder to care for. Seeds from heirloom tomatoes can be kept and seeded the following spring and the new plant’s fruit will stay true to its original tomato. Seeds from hybrid plants will grow if they are planted, but you cannot know what type of tomatoes you’ll end up with because of cross pollination. This means your original disease resistant hybrid plant can produce seeds that will result in diseased plants. Therefore, seeds from hybrid tomatoes should not be used.

How many seeds to purchase and plant?
I usually seed for a lot more plants than I want to keep. Personally I want to start out with at least three times as many plants as the number I actually want to keep, and sometimes I start with two seeds in each cup with the plan to weed out one of them. *More information on this below. By seeding extras, I can select from and keep the strongest ones, toss the weak ones, and share the rest of the good plants with friends and family. But I do often end up with a forest to care for, for a little while!

When and How to Plant Tomato Seeds

Most tomato varieties should be planted 6-8 weeks before the last expected day of frost for your area. For me, in zone 5, that means Memorial Day or end of May. I like to give them ample time, so I plant around March 20th or so.

Personally I find egg cartons to be the perfect starter home for tomato seeds. I put down the date of seeding directly on the “tray”, and sometimes, if I seed different plants in the same tray, I will number each cup and keep track of the different plants in a notebook.

Fill the egg carton trays with potting mix, placing the seeds on top, then covering with more soil. How much to cover with depends on the seeds you are using. You will see this information on the seed packets, and I use this info as approximate debts. You can also fill the cups first, then make little holes for the seeds, stick them in and brush the soil over. Whatever you find easier.

It is best to use a bagged potting mix rather than soil from outside, as potting mix is lighter on tender roots, and clean. Soil from outside tends to pack too much and can carry disease and contaminants that you won’t want in your house or spread to the gardens of people you share plants with. (I will refer to the potting mix as soil in this post, just to clarify.)

*In the following picture (very blurry, unfortunately), you can see some little yellow dots on top of the soil, two in each cup. These are the seeds. I put two or three seeds in each cup and later remove the weakest plants to allow for one in each cup. Some seeds might not sprout at all, especially if they are from previous seasons, so it helps to guarantee you one good plant in each.

For these seeds, I covered with approximately 1/4 inch of potting mix. If you use seeds from your own heirloom plants, a general rule is to cover with soil as deep as the length of the seed; if the seed is 1/4 inch long, cover with 1/4 inch soil. Gently water with a sprayer so that the water flow will not disturb the seeds or cause them to shift. This is a fun job for kids, and my 10 year old son does a great job as you can see on the next picture. I generally have him do two sprays per cup, checking to see how that works out. You’ll want the soil to be damp, not soaked. Holes on the bottom of the cups should not be necessary at this stage with careful misting of water.

Before sprouting, seeds do not require light, but warmth is important. After the sprouts emerge, they should be placed in an area where they receive a lot of light, and temperatures of at least 65 degrees. As they begin forming a lot of leaves, they will require direct sun most of the day. Tomato plants love full sun and warm weather, and will not produce properly without it. I have found my plants to struggle more with disease in years when we have had a lot of rain and overcast.

And make sure you have someone to guard the trays at all times! My guard’s name is Jasmine, or Jazzie for short. You can just tell how she’s scanning the area for potential threats! She’s looking out for us, just like always. Yeah.

To make a tiny, miniature greenhouse, I cover with plastic foil and poke a few holes in it to allow for air circulation. The plastic will help warm up the soil just a tad, and will also help retain moisture to prevent the plants from drying out. I do check on the plants every day, and mist with water whenever needed. Remember: moist, but not wet.

If it should accidentally happen that the soil gets overly wet, you can gently put some paper towel loosely on top of the soil to absorb as much as possible, and remove the plastic until the excess water has evaporated. The soil will pack together when this happens, so it is not an ideal situation. A sprayer will be very helpful in preventing an accidental over-watering.

And here’s the very first little babe!! A little girl! OK, maybe not… But this is getting very exciting! I usually check several times a day at this point, just because I find it so fascinating! These seeds mostly sprouted on day 5 and 6, but this can vary by several days. I had one sprout as late as day 16 this time around.

In the next couple of days, as the tiny sprouts start to grow taller, I often stick down blunt-end toothpicks or similar, in the soil to help hold the plastic up and away from the plants. Otherwise they will not have the room they need to grow. This is now day 7, so it’s only a day or two after sprouting. Some are still working on developing their seed leaves.

Spacing the Plants

The time has come to start spacing the seedlings, to allow for plenty of room for individual plants to grow. Select the strongest plants to stay, and snip away the rest. I keep the ones that look the healthiest, thickest around the stem, and generally have come the furthest. I just snipped off the one I’m pointing to here, …

…and will remove this one too since it’s growing too close to a different one:

Don’t just yank them out, but snip them off gently so you don’t disturb the roots of other plants growing nearby. You can use your finger nails as well; just cut them off. The remaining stem and tiny root system will wither, so you can leave them alone. In another few days I will remove more plants until I have only one per cup remaining.

In this next picture, you can see the beginning of the next set of leaves, which is the first set of true leaves. They started emerging on day 10. As these true leaves develop, you will eventually see the seed leaves, the original first set of leaves, wither and drop. This is no reason for concern. In fact, you should expect this to happen, as the tiny sprout now has used up the nutrition found in these leaves, which was used to sustain the plant in the beginning.

I am now down to one plant per cup, and they are strong enough to handle watering from a bottle rather than the sprayer. This is faster and easier, and I have found a regular drinking bottle with a top on to work very well. I  just give each cup a few dribbles and move on to the next. I have basil growing in the front left cups. Tomatoes and basil thrive very well together and can be grown side-by-side in the garden.

Transplanting Seedlings

When the plants are about 2-4 inches tall with at least one set of true leaves, they should be transplanted to a cup or pot of larger size than the tiny egg carton cups. I just dig them out with the surrounding soil, using a spoon, then transfer to the larger container. Because we had unusually warm weather at the time, I was able to do it outside, but then quickly moved them back inside.

**NOTE: Can you see the tiny hairs on the pink stems? Keep that information in the back of your mind for now…

It is a plus if the container has holes on the bottom for drainage of excess water. You can see the withered seed leaves still hanging on to this plant. They can be removed if you wish.

This next step is very important: Place the tiny root ball quite far down into the pot, then fill with soil. **Remember the little hairs on the stems? Here’s why that matters: When you plant deeply and cover up the stem, all these tiny hairs will grow into roots, which will ensure that the plant has a strong, solid root system. Cool, huh?

So you cover up until you’re about 1/2 – 1  inch from the bottom of the true leaves. The plant looks so tiny buried in the new pot, but it will grow very quickly from now on! Water, then place inside in a sunny, warm spot.

At this point the plants will grow very rapidly; pretty soon as much as several inches a week. That means they will need a lot more water as well. As they grow even taller, I often find myself watering twice a day. With holes on the bottom of the pots, and a tray underneath to catch excess water, I don’t worry as much about over watering as the plants absorb so much of it and the extra drains out. I give a good squirt or two in each pot. Sometimes I just wrap aluminum foil around the bottom of each pot to use as mini trays, and other times I use old cookie sheets to hold several plants.

I usually give away the extra tomato plants once they have been transplanted successfully to larger pots and continued to grow happily for another week.

When they are as large as on the next picture, it is on high time to select the ones I want to keep and get the rest of them out of my kitchen and on to their new homes. They are growing large and will need to be weathered to prepare them for outdoor planting. Weathering means to give them daily outdoor sun and air, a little more each day to help them get used to the outdoors to transition better. I will go into more detail about this simple process in my next post, Growing Tomatoes Part 2: Transplanting Outdoors and Care. In my third post on this subject, Growing Tomatoes Part 3, I will touch on a couple of common problems to be aware of, and what to do in this regard.

This is also a good time to stake the plants if not already done, to help hold them upright. I just use kabob skewers and string.

Very soon, the teeny, tiny sprouts will look like this, and indeterminate plants will only keep on growing from here:

My post Growing Tomatoes Part 2: Transplanting Outdoors & Care includes great information about how to transplant to large pots or in-ground, as well as general care. And in Growing Tomatoes Part 3, Common Problems & Solutions, I go through diseases and disorders and what to do to prevent or treat. I also have a post on tomato hornworms as these fascinating but destructive worms deserves a chapter all to themselves! They will make you choose between them and the tomatoes!

Seeding, transplanting seedlings, and growing larger tomato plants is quite easy, as you can see on these pictures. It is also very rewarding when you see your wonderful harvest of red, flavorful, homegrown tomatoes that you have grown from they were tiny seeds! Just a little bit of information on how and when will go a long way in knowing what to do to be successful. What a miracle, the life and potential that God has placed in these little seeds that are now producing scrumptious and nutritious food for your family!

About Terese

19 Responses to “Growing Tomatoes Part 1: Seeding & Transplanting Seedlings”

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  1. Kathy says:

    Thanks so much for the information and the pictures. For the first time I am going to plant some seeds for beefsteak tomatoes and also sweet peppers. Going to use the egg carton method you mentioned. I have a balcony that gets lots of good sunlight.

    • Terese says:

      That’s great! Just be aware that beefsteak tomatoes are extremely large and can be very heavy for the plant to carry, so you may want to stake these plants very well to help support it. I hope you’ll have a lot of fun and that you’ll have an abundance of awesome tomatoes come July / August!

  2. Nicole says:

    Thank you so much for this post and pictures!! I haven’t ever tried seeds before, but started last week. I saw a post on Pinterest using used paper towel rolls to plant and unfortunately there is white fur (gross) growing on the outside of two. I will use your egg carton trick for thenext batch. Are they too tiny to move into another container? I’m learning on the fly! Thanks!!!

    • Terese says:

      Sounds like they might be growing some mold. My guess is that you’re over watering, and that’s why the white fuzz has developed. You could try to let them dry out some, to stop the mold from growing. It seems like they should be fine. Don’t let them get entirely dry and hard, just barely moist but not wet until it’s under control. Then keep them moist on top but not necessarily all the way to the bottom until the roots develop more. Since you already have them planted, I would personally try to keep them there. But if you really want them in egg cartons, I would try to transfer these plants you already have rather than giving up and starting over. Egg cartons can be convenient, but they are very tiny, so it won’t be too long and they’ll grow out of them. You should still only have to transfer once before you plant them outside. So I do like them.

  3. alice says:

    I used old muffin tins with the paper liners to start seeds. They are very easy to remove for transplanting and the paper liners are bio-degradeable

  4. Pat Hendriks says:

    I found your site through Pinterest and I must say I’m very impressed with this article on starting tomatoes from seeds. I reposted it to my Pinterest board, and my facebook page ( for others to see.

    I’m curious, do you add any amendments to the potting soil? And do you use a generic potting soil or one especially for starting plants?

    Thank you so much for this detailed article and the great photos.

    Pat Hendirks

    • Terese says:

      Thank you, Pat!
      No, I do not add anything to the soil, and I’ll use either potting mix or seed starter, whatever I have on hand. Both have worked for me. One year I even grabbed soil from my own garden, which worked, but not as well. I found that it hardened a lot more when it dried between waterings, and of course there is always the risk of pests or disease. So I otherwise always use seed starter or potting mix. When I replant into bigger cups, I’ll use some type of soil and not just the starter mix.

  5. Olya says:

    Thank you so much for this post! I was hoping to grow tomatoes from seeds this spring and had no idea where to begin! This gave me the confidence to give it a go!

  6. Nicki says:

    This is a great article thank you! I live in idaho and am considering starting my seeds early just to get a jump on my growing season.

  7. Irina says:

    Hi Teresa,
    Love your site!
    I am a beginner, I used to plant tomatoes from the nurseries, but unfortunately I cannot find my favorite type-whopper, so I decided to grow them myself. I had bad experience, my tomatoes got leggy and died….
    Question about what type of soil to use when your planting the seeds. You used the pot mix soil, what about “seed starter mix”?
    Also where do u buy the seeds, any good on line stores?
    Many thank!

    • Terese says:

      Potting mix or seed starter are both fine to use. I’ll use either one. I often purchase seeds directly from plant centers in our area, otherwise I’ve also purchased from Territorial Seed company online. Last time I ordered I purchased from Trade Winds Fruit online because their prices are lower. Especially shipping. If you purchase one envelope, it’s $8 at TSC, and $5 at TWF.

  8. Lynda says:

    I found that wicking the small starter containers with a hole in the bottom and put a piece of shoe string through allowing the string to be in the container and in the bottom holder of which has water to wick up to the soil.

  9. Rykiel says:

    I can say thank you enough for this walk through! Ah! I was doing it all wrong and they just kept dying. Thank you, thank you!

    • Terese says:

      I’m sorry you had previous struggles, but glad that I could help! Hope things will go better this time around. At least you haven’t given up, that’s good! Have fun with it!

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