If you’ve followed all of the steps in part one of this tutorial, you will now have baby tomato plants, each with two little leaves:
Sometimes the seed will still be stuck on the leaf, but don’t worry about it. These aren’t true leaves, but cotyledons, and they help to feed the plant until the first true leaves emerge and start photosynthesizing. The most fragile part of the plant right now is the stem. It is very thin and easily damaged–if that happens the plant won’t be able to continue to grow.
What your seedlings need you to pay close attention to at this stage of their growth, and for the next few weeks, are appropriate water and light.
Water and Watering
Tomato seedlings, like most plants, don’t like to have their feet (roots) sitting in water; they will rot. But they also can’t tolerate drying out, and because they’re growing in a small quantity of soil, that can happen quite quickly. Check them every day and strive to keep the soil evenly moist.
Water must be delivered to the plants in a gentle manner–pouring water directly from the spout of a watering can onto seedlings can knock them over and/or break them, as well as displace the soil that they’re growing in. Either water them from below (i.e. pour water into the tray they’re growing in, let it absorb for half an hour, and then empty the tray of whatever remains) or water them with something that will provide a gentle flow. If you only have a few plants you can get away with misting them generously with a spray bottle, but this gets hard on your hands if you have a lot of plants.
The DIY version of this is to take your smallest drill bit and drill holes in the top of the cap of a plastic soda or water bottle.
Lights and Lighting
In order to develop strong, healthy seedlings (and not gangly ones that will flop over), you need to provide bright direct light for about 16 hours a day. Ideally, this light should be provided close to the plants (one to two inches if you’re using fluorescent shop lights, further if you’re using hotter lights–more on that below) above the plants.
This either means having your lights hanging on some sort of a setup where you can raise them as they grow, or propping your plant tray up close to the light source, and removing layers of support as the plants grow (e.g. if it’s sitting on a pile of books, remove a book at a time from the pile as the plants get taller in order to maintain the plants at a distance of one to two inches from the light).
I grow my seedlings on a metal plant stand. The fluorescent lights that came with the stand has bolt and washer contraptions at each end that allowed me to loosen them, adjust the height, and then screw them tight again. Over time the ballasts on those lights failed and I replaced them with other shop lights that had two metal chains on the top, that I hung to the stand with s-hooks. When I needed to raise or lower them, I just inserted the hook into a different link on the chain. This worked pretty well but was a little bit awkward. I recently discovered, and have fallen in love with, these ratchet hangers*:
I use two per light. I clip one end to the light stand, the other end to my light, and raising and lowering the lights is now almost effortless.
They are just one of the many innovations I’ve seen come on the market for indoor plant growers since growing cannabis became popular and legal (in some areas, like Canada). It’s not a crop I’m interested in growing, but I’m happy to take advantage of the related products if they help me grow better tomatoes.
Speaking of which, there have been a lot of innovations in the actual lights used for indoor growing. It used to be that if searched for grow lights (on mainstream websites) you’d find a bunch of shop lights with fluorescent tubes. If you were going to get fancy you’d look for fluorescent tubes with full spectrum. Well, with advances in LED technology and the interest in cannabis growth, a search for “grow lights” is now likely to show you a listing of very fancy LED light arrays, often pink, and often priced well over $100. This is not what you need for growing tomato seedlings. Sure, they will work, but they’re way more than your little seedlings need. Those light displays are for gardeners who are trying to take their plants from seed to flower to full maturity, completely indoors.
If you’re growing tomato seedlings, all you need to do is get your plants from seed to healthy little plant, ready for transplanting outdoors. I use standard shop lights, but have replaced the fluorescent tubes with LED lights. The general rule with fluorescent shop lights was to keep them one to two inches above your plants. From what I’ve read, many of the LEDs on the market now are much brighter and could be too powerful for young seedlings if used so closely. The recommendations are to use what you have and watch your seedlings closely–if the leaves have any crispy spots they’re too close to the lights; if the stems are stretching out and looking scrawny they’re too far away from the lights.
If you would like a more concrete recommendation on lights, this post is the best discussion I’ve come across about the many different lights available for seed starting, what to consider in figuring out distances, and which ones to buy.
To make the most of the light coming out of my light fixtures I use a little trick my father taught me, and wrap my light stand in a foil emergency blanket. I purchased mine from a local dollar store, but they are available online* as well.
Water and light are the most important factors to growing healthy seedlings, but once they’ve developed true leaves to really get them ready for their journey to the big, windy world outdoors, it is best to strengthen their stems by keeping a small electric fan blowing very gently over them, or by running your hand lightly over the tray of seedlings once or twice a day. If you use a fan, start off by only using it for a short time, and keep in mind that the breeze from the fan will dry out the seed starting mix faster than without, so adjust your watering accordingly.
There are fans available specifically designed to clip onto growing setups*, but many gardeners, myself included, do quite well with nothing more than a cheap mini desk fan*. Some years I don’t bother setting it up and just run my hands over the plants instead.
Take Care of Your Seedlings
Pay attention to the above and keep a close eye on your seedlings. Part 3 of this series will discuss thinning out tomato seedlings, transplanting up to a bigger pot, and hardening off.
*Disclosure: some of the links on this page are affiliate links, meaning, at no additional cost to you, I will earn a commission if you click through and make a purchase.