A step-by-step guide to growing tomatoes from seed
Why start your own tomato seeds when you can pop into your local nursery and buy ready-to-plant seedlings? The most important reason is variety! Your local nursery may have a dozen just about varieties of tomatoes, but growing your own tomatoes from seed allows you to pick from thousands of heirloom, hybrid, and open-pollinated varieties available through seed catalogs. Plus, starting your own tomatoes can economize, especially if you have got a large garden.
Sow seeds at the right time
Growing tomatoes from seed take about six weeks to two months from sowing to transplanting. Starting seeds indoors too early brings about leggy, overgrown seedlings. I aim to transplant my seedlings into the nursery about seven days after my last expected spring frost date. Find out the last frost date for your region and count in reverse by six to eight weeks. That is when you should sow your seeds indoors.
Use clean containers
I start a LOT of seeds each spring and need to utilize my growing space efficiently. Therefore, I sow my seeds in plastic cell packs placed on 1020 trays. They are reusable and I can pack plants under my grow lights. You can also use plastic pots or recycled clean yogurt containers, milk cartons, and so on.
Plant tomato seeds in a high-quality potting mix in clean containers.
I like to start my tomato seeds in cell packs inserted into 1020 flats. This allows me to fit a lot of seedlings under my grow lights.
Use a high-quality seed starting mix
Give your tomatoes the right start with a lightweight, well-draining growing medium like Pro-Mix Seed Starting Mix. Moisten the mix before filling pots or cell packs to avoid uneven wetting.
Plant seeds at the right depth
Tomato seeds are small and if you plant them too deeply, you’ll never see them again. Sow them about one-quarter inch deep, covering lightly with moistened potting mix. Label each variety with a plastic or wooden tag and the name written in permanent marker (trust me, you won’t remember which is which if you don’t label them).
Provide plenty of light
Sturdy, healthy seedlings need plenty of light. Too little light results in legginess where the seedlings reach and stretch, eventually flopping over. The best spot to start seeds is under a grow light, where you control the amount of light. My grow lights are inexpensive, four-foot shop lights hung with chains on a wooden shelf. As the plants grow, I can move my lights up so that they are always just a few inches from the foliage of my tomato plants. I leave the lights turned on for sixteen hours per day, and have a time regulator that turns them on and off. You can use a radiant window to start tomato seeds, but due to low light conditions in pre-spring, expect some stretching. If you plan on making seed starting an annual event, consider investing in a grow light, like this fluorescent fixture or a SunBlaster.
Use grow-lights to grow healthy seedlings
To grow healthy, sturdy tomato seedlings, leave your grow lights on for 16 hours every day.
Overwatering is one of the quickest ways to kill delicate seedlings, so keep an eye on soil moisture. It should be slightly moist, but not soaking wet. Once seeds are sown, use a clear plastic dome or a sheet of plastic wrap over the top of the trays and containers to maintain moisture. Once germination occurs, remove all covers so that air can circulate.
Provide adequate air circulation
As indicated in my previous step, air circulation is important when growing healthy tomato plants. My grow lights are set up in my basement where there isn’t a lot of air circulation. This could lead to fungal issues if I didn’t have a small oscillating fan in the room to move air. Having moving air also toughens up the stems and foliage of the seedlings.
Feed the seedlings
Many potting mixes contain slow-release fertilizer to feed your plants slowly over several weeks. You can supplement these fertilizers with organic water-soluble fertilizer, applied at half the recommended rate every 12 to 14 days. Carefully read and follow all labels on potting mix bags and fertilizer containers.
Harden off tomato seedlings
You’ve reached the last step of growing tomatoes from seed! Once you’ve reached the final spring frost date, it’s time to harden off your tomato seedlings. Hardening off is the process where indoor-grown seedlings are acclimatized to the outdoor garden. Expect this process to take five to seven days. Start by putting the seedlings outside in the shade for a few hours. Bring them back indoors that night. Continue to put the seedlings outside, gradually introducing them to more sun each day. They are ready to be transplanted into the garden or containers within a week.read more