Tomato Starting and Transplanting Tips

(As of the time of this posting–it’s too early. Wait a few more weeks! I generally start tomatoes in mid-to-late March. At the latest, a few days before I can get out and plant peas.)

I start tomatoes, peppers, and eggplant in re-usable black plastic germinator, or “channel” flats–they are shallower than regular flats, and instead of little pots, they have long channels to put the soil and seeds in. When my tomatoes get big enough to have to “pot on,” or transplant, into bigger pots or cells, I want to make sure I can be putting them outside most days (and taking them in at night) rather than trying in vain to fit the six or eight flats full of them under my lights inside, along with all the peppers and eggplant as well.

I usually let the peppers and eggplant stay cozy inside a bit longer, as they are a little more cold-sensitive than tomatoes. I’ll put my tomato starts outside if it’s in the mid-sixties, but I don’t put peppers or eggplant out unless it’s in the mid-seventies or warmer.

Each germinator flat has about twenty channels–I use one flat to start all of my tomato varieties and one for eggplant and peppers together (they get started about two weeks earlier than tomatoes). When I use the germinator flat, I get a little extra time before the plants need to be moved into larger pots (I re-use 4-packs), and I don’t have the problem of either thinning out a bigger pot with more than one plant in it, or empty pots taking up space because the seed sown in them turned out not to be viable.

You do have to be a little delicate separating the roots of the seedlings started this way–if there are a lot of seedlings in one channel, you may lose a few. So, try to plant only 12-15 or so seeds in each channel unless you’re concerned about the viability of the seed. Same goes for the amount of seed you start in any “group pot.”

Also, with the two-week time lapse between the eggplant/pepper seeding and the tomato seeding, I can use my single seedling heat mat (basically a water-resistant heating pad for plants) to give a little extra warmth to the eggplant and peppers until they come up and get growing, and then switch it over to the tomatoes. Once the tomatoes come up, I often switch the heat mat back over to the peppers and eggplant, but not always.

Another bonus to this strategy is that it saves space–by the time I’m ready to put all the tomatoes, peppers, and eggplant into their 4-packs, which ends up taking 8-12 full flats instead of two germinator flats, the cold-hardy leeks and onions are ready to go out to the garden (or at least can live outside until I’m ready to transplant).

If it doesn’t sound like you could start that many tomato plants in one of these little germinator flats–I can get 200-250 or more plants germinated out of one. The trick is to move them up to bigger quarters as soon as they start getting their “true leaves.” True leaves are the ones that actually look like the plant’s mature leaf, rather than the simpler seedling leaf.

With tomatoes, when you transplant them, you can sink the seedling stem into the soil up almost to its lowest set of leaves, and the plant will grow new roots along its stem. This makes the plant much more sturdy. You can repeat this process when you transplant them out in the field, too.

If you start tomatoes too early (say, now), you risk having them get cramped in their 4-packs and have to pot them up to an even bigger size before they can go in the field. That wastes potting soil and stresses the plant unnecessarily.

Those huge plants you get in the supermarket greenhouses (some already with fruit!) are way too big. They want to make them look huge and lush, but honestly, a lot of those commercially-grown plants are too big (hopped up on chemical fertilizers), by the time they get to the stores, and they won’t bear as well as a smaller, sturdier seedling started later.

I know, I know, the temperatures are rising–you can almost see spring! Start some onions, leeks, or parsley now, and leave the tomatoes alone for a few more weeks.

Another small tip: though I’ve used a seed-starting mix with worm castings this year, I generally will use a little fish/seaweed emulsion in the water when I’m transplanting them (both into 4-packs and into the field) to help reduce transplant shock.

I also mix a little aged/composted manure of whatever type I have on hand into the hole when I transplant into the field–rabbit last year, but buffalo chips, cow, or horse manure all seem to work well.

Once I’ve dug the hole, loosened it up well for good drainage, and mixed in the manure, I put the fish emulsion water directly into the hole, place the plant in up to its first set of leaves, and backfill–not tamping too hard–just enough to eliminate big airpockets.  That way, the moisture is in direct contact with the roots, and you’re not overhead watering, which can be very damaging–especially to young plants on a sunny day.

If, when you pour the fishy-water in the hole, it doesn’t start to drain away fairly quickly, you need to do a little more soil loosening.  You don’t want to end up with a tomato plant in a pool of water–you just want the soil to be moist.  We have heavy clay soil, so loosening and adding amendments is key–if you dig a hole and the sides are slick with clay–the tomato plant’s roots will have a hard time spreading out.

I do not have too much problem with cutworms–so I don’t use collars around the seedlings.  In fact, I usually have so many tomato plants that if one gets “cut,” I dig around and find the cutworm and kill it, then replace the plant.  I will usually use a little slightly aged grass clippings or straw as a mulch around the base of the plant.

After you place the plant, backfill and mulch, you can “water in” the mulch if you want to help it stay put.  Just try not to get water on the leaves of the plant.  If you’re using a cage around your plant, you can place it now.  The big indeterminate (vining rather than bush) tomatoes like Brandywine need a very sturdy trellis or other support system.  A regular tomato cage cannot support them.

I use cattle panels wired to steel “T” posts set up in advance, so I can succession plant peas, then tomatoes, on them.  If you stagger the cattle panels around the garden, you can use their ends to anchor a webwork of electric fencing if you have a deer problem.  You do need to make sure the plants don’t grow into the wire though, as that will short it out.


7 responses to this post.

  1. Posted by Marcey Bothe on June 11, 2008 at 12:16 pm

    Can I transplant a tomatoe plant when it’s bearing fruit? I started the pot too small and it’s starting to have fruit already and I can see that the pot is way too small.

  2. Posted by flyingtomato on June 11, 2008 at 5:07 pm


    If you really want to transplant it, remove the fruit and any blossoms, and transplant fairly deep (up to the first true leaves).

    Your tomato is in fruiting mode, so you want to give it this signal to develop a better root structure and work on growing bigger rather than focusing its energy on fruiting.

    However, I would not expect to get as good a harvest off a plant that is already starting to fruit when you’re transplanting it.

    You’ll likely have better luck if it’s an indeterminate plant rather than a bush tomato.

  3. Posted by Solana on July 19, 2009 at 7:00 am

    Hello, I was hoping to get some advice on my tomato plants. I planted 6 roma and 6 cherry tomato plants in a small container garden. I see that they are becoming too large for the container and I was hoping to transplant them but I am not sure if its too late to do it? Only a few of the bushes have started producing fruit and they are about 1-2 feet tall right now. I am worried that I will lose them completely and if I should just leave them be? I see that I will not get alot of fruit out of them if I leave them so crowded in those small containers..I under estimated the space I had to grow them. Any advice would really really help. Thanks! S-

  4. Posted by flyingtomato on July 19, 2009 at 7:50 am


    If they are in a container, their roots have probably grown together too much to transplant. My best advice is to avoid transplanting, and probably shocking or killing them (esp. if some are already producing fruit). Cut some of the plants out at ground level instead. You’ll sacrifice a few, but your yields and health of remaining plants will be better (not to mention constant watering will be less of an issue). I don’t know how big your container is–but it’d have to be really huge to hold twelve tomato plants!

    Good luck!


  5. Posted by Solana on July 19, 2009 at 10:47 am

    Thanks. Ye, they are small plants..i figure I sort of blew it, although some of the plants are really strong and healthy..I guess I will have to wait and see what happens! There is one plant in each species that is very weak and the stem is thin and looks breakable..probably being suffocated by the roots? Thanks again!

  6. Posted by Solana on July 19, 2009 at 10:48 am

    do you think trying to transplant one and see how it does makes sense?

  7. Posted by flyingtomato on July 19, 2009 at 9:16 pm

    I would take out the weakest ones with the thinnest stems.

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