Tomatoes are a favorite summer time treat for gardeners. If you’ve ever tried a home grown tomato, you’ll know just how amazing they taste! You’ll never want to eat one from the grocery store again. Tomatoes come in a seemingly endless array of colors, shapes, and sizes. Even the taste can vary greatly from variety to variety. However, often times local garden nurseries only carry a limited selection. Starting your own tomato seeds opens you up to a huge selection. Let’s walk through the process of how to grow tomatoes from seed.
All About Timing – Days to Harvest
You can find the “days to harvest” information on seed packets or on plant tags if you buy seedlings. When you use transplants, the days start counting when it has been planted. When direct sowing, the days start when the seed is sown. For ornamental plants, harvest is when the first flowers open. For vegetable gardening, it’s when you can harvest the first fruit or vegetable.
This number is not exact because there are MANY factors that can change your actual days to harvest but this will give you a general idea. However, it’s especially useful when trying to decide which varieties to grow. If you garden in a cooler or warmer zone then this is an important bit of info to pay attention to. I’m in Zone 9a in the Mojave Desert. It quickly gets too hot for tomatoes during the summer so we need to choose varieties and plant them early enough to get a solid harvest before we hit triple digits for the summer. In cooler climates, you’ll also have a short growing season.
When to Sow Seeds?
Since I know when I’d like to start harvesting tomatoes, I like to count backward to see when I should start the seeds. My first harvest goal is early May. Most cherry and grape tomatoes have a “days to harvest” of around 70 days. So, that means I want to get my tomatoes in the ground in mid-late February. That’s difficult to do even with our mild winters so I use season extenders to plant them earlier than normal. Larger tomatoes usually take longer but there are some fast maturing varieties that won’t be too far behind the cherry tomatoes. These are the varieties I like to choose because of our short growing season.
In colder climates, when you plant in the garden is determined by the ground temperature and, of course, snow melt. The best way to know when to plant anything is to consult local gardening resources like your cooperative extension. When you know when you can plant, count back about 4-6 weeks and start your tomato seeds then. Give your seedlings more time if you like larger seedlings to plant.
Related Post – Get an Early Start on Tomato Season
Soil Blocks in tray
Starting the Seeds
If you have older seeds, you can check the germination rate before starting the seeds. This will tell you how many of the seeds are viable. You may find that some are not good at all. This can save you the time and frustration of planting seeds that don’t germinate.
My favorite way to start my own seedlings is to use soil blocks. These are tightly compacted blocks of soil that sit by themselves without being in a cell tray. Seedlings in cell trays can be very difficult to get out (no matter what the marketing tells you). I lost quite a few seedlings even when I was very careful. I’ve never lost one using soil blocks. You can check out how (and why) I use soil blocks for starting all my seedlings.
I always plant 2 seeds per soil block just in case one doesn’t germinate. Even brand new seeds won’t have a 100% germination rate. This gives me a better chance of having a full tray. This also is a good use of space if you don’t have much space for seed trays. If both seeds germinate, use a small pair of scissors to clip off the weakest one at the soil. Using a heat mat under the seedling tray will help speed up germination. You can also use the top of refrigerator but I’ve had better success with a heat mat.
Related Post – How to Start Seeds in Soil Blocks
Do I Need a Grow Light?
Many new gardeners are encouraged to just use a south facing window to start their seeds. This may work to some degree but you’ll have much better success if you use an actual grow light meant for starting seeds. Sunlight from a south facing window isn’t strong enough to produce strong healthy seedlings…even here in the hot desert. Seedlings often turn out leggy – meaning the stem grows really long and thin as the plant reaches for light.
If space is limited, you can use this type of grow light which is what I started out with when I finally gave up on the window. It worked well and didn’t take up much space. After a year or two, I graduated a grow light I found at a local hardware store. I have no idea what it is because there’s no brand or model # on it. However, this no-name light worked much better. My seedlings grew faster and were healthier. Now, I use this grow light and I absolutely love it! This is my first year using it and even my husband noticed the difference. You can also buy pre-made shelving units that have grow lights built in but often those products don’t have the specs available for the lights. That makes me nervous so I opted to buy a great light and fit it on a regular metal shelf.
Potting up Tomatoes
Potting Up
Pot up your tomatoes when they have two sets of true leaves. The first leaves to appear are the cotyledons, then the true leaves come. Some people, especially those that like large tomato seedlings to transplant, may pot up the tomatoes twice before finally transplanting them into the garden. That’s a bit too much work for me. I use 1 gallon sized containers and that’s where they stay until planting. I use the same seed starting mix in these pots that I use for soil blocks. Reuse plastic nursery pots, or you can also use quart sized yogurt containers. Just make sure you punch drainage holes in the bottom of it.
Tomatoes will grow roots along the stem that is buried under soil. This helps the plant develop a large root system that can support the plant. This is especially important with those giant indeterminate vine varieties. Position the tomato seedling at or near the bottom of the pot. Leave 1-2 sets of leaves sticking up above the soil. Pick off any leaves that will now be under the soil. New roots will grow from there too.
I usually aim to have the tomatoes in these containers for 2 weeks but using 1 gallon containers gives them space if planting gets delayed.
Hardening Off Tomatoes
Hardening Off
This is the process where your indoor grown seedlings are slowly introduced to the outside world. Generally, you want to start the process at least 1 week before planting seedlings in the garden. Gradually expose your seedlings to full direct sun. The first day should only be an hour or two in a heavily shaded area. You should be able to leave them in full sun all day around the 7th day. I like to use a cold frame if the weather is a bit too cold or windy.
Since tomatoes are potted up, the hardening off stage can last longer depending on your space. If you don’t have space under lights for the potted up tomatoes, plan to harden off the seedlings either right before potting up or right after. I don’t always have space for the larger pots indoors, so I usually harden off the tray of seedlings and then keep the potted up plants in a cold frame because it’s usually still a bit cold for them outside at this point. I keep my tomatoes in these pots for 2-3 weeks before planting but they can stay much longer since I use larger containers and only pot up once.
Planting Tomatoes: L – Check planting depth, C – Healthy roots that don’t circle, R – Just the top 2 sets of leaves stick up.
Planting
Pay attention to spacing requirements on the seed packets. You can also find spacing recommendations with many different gardening styles like Square Foot Gardening. Dig a hole deep enough so that only the top 2-3 sets of leaves will be above ground. Tomatoes like to be planted deep! Place the pot in the hole to check depth. Pick off any leaves that will be buried. Roots will grow along the buried stem. I recommend using compost to amend the garden, an endomycorrhizal inoculant, organic fertilizer, and greensand or azomite. I also use water soluble kelp after planting and weekly for the first few weeks. Don’t forget to continue to fertilize your plants according to label instructions. Tomatoes are heavy feeders.
Tomato Cages and Supports
The tomato cages sold locally are absolutely pitiful…at least where I live. I sometimes use them for peas and maybe determinate tomatoes but that’s it. You can many find heavy duty tomato cages and supports online. I highly recommend you get something and have it in place soon after planting. If you wait too long, the plants can get out of control. It’s difficult to get a cage around them at that point. I’ve used Texas Tomato Cages for years. After the first year, I bought several more to use for growing peas, beans, and cucumbers vertically.
Tomatoes are one of the most popular crops for backyard gardeners but we are often limited to just a handful of varieties that local nurseries stock. Growing our own tomato plants from seed opens up a huge selection of varieties. Plus, we can start them earlier and kick off tomato season ahead of everyone else by planting early with season extenders. What are your favorite varieties to grow from seed?
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