Starting Tomatoes from Seed

Tomato harvest. Photos by Laurie Neverman.

I grow all my own tomato plants from seed, and in an average year I’ll raise over 100 seedlings.  Around 30 go into my garden, the rest are shared with friends and neighbors.

Here’s my approach to starting tomato seedlings.

Choose a Good Potting Medium, Plant at the Right Depth

I like to use a mix of potting soil and worm castings (3:1 ratio), in individual cell packs. You may want to do a quick soil test on your potting mix before you start, as many on the market are lacking in key nutrients and/or overloaded with other nutrients.

Plant seeds roughly three times as deep as the seed is wide, tamp soil gently.  I like to mark my seeds using popsicle sticks broken in half.  I write the name of the variety on both sides of the stick with a ball point pen (in case it gets it gets wet, which it will, generally one side remains readable).

Cover the seed flat with a clear plastic cover or bag, and put it in a well lit location.  I like to give them a little jump start with a heating pad underneath.  I put the heating pad and the lights on a timer, leaving them on for about 16 hours a day.   If you'd like some more photos of my planting bench and seed starting setup, take a peek at this post.

Once the Seeds Sprout - Troubleshooting

Once you get seedlings popping up, uncover them within the first 24 hours. Keeping them covered can lead to damping off.  Damping off results from fungal infection.  It generally comes from keeping your seedlings too wet.  One day they'll look fine - then WHAM!  The seedlings are laying there dead.  Generally the stem shrinks up near ground level, and the soil is very wet.  Sometimes here will be mold or fuzz growing on the surface of the soil.  (Yes, I have made this mistake - it's not pretty.)  A sprinkle of cinnamon  or a spritz of chamomile tea may help save the remaining seedlings, but once a plant has keeled over, it's a goner.

If the color of your seedlings is off - check moisture levels.  You want damp soil, not too wet or too dry.  If the moisture level seems fine, try a soil test.  As I mentioned above, some soil mixes are just not right.

If your seedlings are really tall, skinny and floppy (AKA "leggy") - chances are your lighting is inadequate.  Try a different location or more lighting.   Putting a fan on a timer and having it blow on the seedlings off and on through the day will also help toughen up stems (and prevent damping off and other diseases - ever wonder why they have those fans running all the time in commercial greenhouses?).  Alternatively, you can run your hands lightly across the tops of the seedlings from time to time during the day.

If you've got leaf tips that are pinched together by a seed that didn't fall off, like the one pictured below, it is okay to gently remove the stuck seed.  Try not to tear the leaf. This will go a little easier if the seed is moist.

Before and after. Photos by Laurie Neverman.

As the tomatoes get larger, they can be moved into a greenhouse or cold frame - just make sure to keep them from freezing (preferably between 50-80F).

Transplanting

As my seedlings grow, I transplant them into larger containers.  First, I'll move them to two inch containers, then up to three or four inch, depending on how fast they're growing and how long until I can get them in the garden.  I have seen some gardeners recommend cutting off the excess seedlings in each cell at ground level with a scissors and keeping only the strongest, but I just can't bring myself to kill healthy little plants. Gently pry a group of seedlings out of their cell, pushing up from below as you pull from the base of the plant above.  Ease the roots apart, trying to keep as much soil as possible on the roots.

Seedlings ready for transplanting. Photos by Laurie Neverman.

Transplant seedlings as deep as possible in their new container.  This will help support the stems.  Yes, it's okay if bottom leaves are covered.  In a few weeks, I graduate the plants to the larger pots.

When it's getting close to the time to plant them outside, I start hardening them off. "Hardening off" plants is the process of gently introducing them to the outside elements to toughen them up enough to survive in the garden.  You want to take it slow, or you'll end up killing all your little seedlings.  I prefer to harden them off over 3-4 days, starting them out with no more than an hour or two of direct sun the first day and increasing exposure each day.  Make sure they are protected from the wind and adequately watered when you set them out.  A little extra TLC at this point goes a long way.

When you plant them in the garden, I prefer deeper holes over shallow trenches. Planting deep (just leaving a few inches of leaves exposed above ground) will yield a more robust, more drought tolerant plant.  The plant will send out new roots from the buried stem.  I add a small handful of crushed eggshells to the planting hole to help prevent blossom end rot, which is caused by inadequate calcium levels and is generally made worse by fluctuating moisture levels in the soil.  Tomatoes like rich soil, so I also add some well rotted manure or worm castings, but you don't want to add too much (a shovel full per planting hole is enough).  Too much nitrogen will give you too many leaves and not enough tomatoes.  I also mulch, trellis and often add a soaker hose under the mulch for watering.

I hope you’ve found this post helpful.  For more on seedling identification and the story of kitty’s wild night in the greenhouse, view the extended version of this post at Tomato Mania on Common Sense Homesteading.

You can also visit the Common Sense Homestead on YourGardenShow.