Garden Republic's Guide to Growing Heirloom Tomatoes

Garden Republic's Guide to Growing Heirloom Tomatoes

Do you have the grow-your-own-tomatoes-itch? I know we do! We've recently added two different tomato options to our shop and want to make sure you have all the tips and tricks you need to know to grow tasty tomatoes from seed to a healthy mature plant! 

Tomatoes are pretty easy to grow from seed, but there as a few things to keep in mind and steps that one should take to have the best success. We've put these below in an easy-to-read guide.

What you will need:

  • your favorite varieties of tomato seeds
  • seed starting soil
  • watering can
  • 3"starter pots/starting trays with drainage
  • 10 hours of sunlight( or grow light)
  • Organic plant food
  • tomato cages/ladder/trellis ( for mature plants)
  • Fan *optional
  • 3+gallon pots for transplanting (if plants are not going in the ground)

Sowing the Seeds:

  1. You'll want to start by soaking your seeds for about 12 hours ( you can do less, but not more!) between damp paper towels. You only need to soak 2 or 3 seeds per pot ( or 1 if you use a tray with small cells).
  2. After soaking, you'll want to plant them immediately, so have the pots prepared with soil right beforehand and have the soil thoroughly moisten. Place the seeds on tops of the soil, then cover with a light layer of soil ( about 1/4th of an inch)
  3. Since the pot's soil should already be pre-moistened, you just need to do a light watering, just enough to get that top layer of soil wet. Be careful not to water-aggressively. More than a gentle sprinkle/mist can dislodge and drive the seeds too deep in the soil. 
  4. Keep the seeds warm! A constant soil temperature is going to be critical to optimum sprouting and soil health. Although a heating mat is not necessary for getting your tomatoes to sprout, it may be incredibly helpful in circumstances where your temperature is going to fluctuate due to light exposure (such and a sunny window). They do not need hot soil, but rather a soil that stays constant, as they would experience if they were planted in the earth. The earth is a magnificent insulator and works to keep the soil at a constant temperature, pots are not! Keep your pot placement away from any drafty windows, and you should be just fine!
  5. Check your plants daily and make sure you keep the soil moist. 

 My seeds have sprouted!

As soon as your seeds have sprouted, they will need lots of light to continue to grow past the cotyledon stage! If you're using an LED grow light, you'll need to make sure that it runs for at least 10 hours a day. If you're using a conventional "bulb-type" grow light, you can run it from 8-10 hours. Failure to supply your sprouts with enough sunshine will deprive them of their primary source of energy. If you're relying on the light of the sun to get your sprouts to thrive, be prepared for temperamental little plant babies on cloudy days. As a fruit-bearing plants, they have high energy requirements. Even one cloudy day can zap the energy and growth of your little plant!

If you are using a windowsill/natural sunlight to grow your sprouts, rotate the pots daily to help them grow straight and not leaning to one side!

Think about the last tomato you sunk your teeth into. It was juicy, messy, and delicious. That messiness comes from a very high concentration of water. This steady supply of water needs to start when your little guys are just in the seedling stage. Don't be shy with the water once they pop up. They'll be thirsty and looking to you to quench their thirst. Monitor the average hydration of the soil, and make sure it stays damp but not soaking. Soaking wet soil can lead to rotten seeds, mold, and other undesirable soil conditions. All soils are different, so never rely on watering every day or on certain days. The water requirements for sprouts can vary from day to day, depending on their growth rate!

Plant food
Once your tomato sprouts have developed their second set of leaves, they'll be getting hungry. It's time for plant food! A water-soluble, organic tomato fertilizer is the best route to go, as this will reach the roots the easiest. 

Aside from needing a little extra calcium, it is crucial to feed your 'maters with a well-balanced food rich in Potassium. This Potassium is what your tomato will use to set flowers, which will eventually turn into tomatoes. Avoid using any "all-purpose" fertilizers that promise to make your plant grow like a "miracle" (wink, wink). Select a formulation closer to 1-3-3 or 5-10-10 or even 5-5-20. You'll see that the more synthetic the fertilizer, the higher the numbers. A personal favorite for use with tomatoes is Tomato-Tone.

One of the most common issues with growing tomatoes is nutrient-related. Since they are incredibly high feeders, it is not uncommon for them to gobble up nutrients very quickly. When you're growing anything in a pot, there is no natural way (or very little) for organic matter and nutrients to be reintroduced into the soil through decomposition. This lack of normal decomposition restricts the presence of certain micronutrients, some of which are crucial to tomato success. Micronutrients such as iron and calcium can be the defining factor between you having an edible tomato and having a nasty 'mater with blossom end rot. Our favorite way of circumventing the "it's too late" scenario is to add gypsum to your soil as soon as you transfer your little sprout out of its pot.

Thinning out your sprouts:
For the strongest, healthiest sprouts, you'll want just one seedling per pot or cell.  Thinning is challenging for many gardeners; who wants to destroy sprouts you've worked so hard to grow?! But it has to be done. Select the strongest, healthiest seedling and use a pair of scissors to snip off the others at the soil line. You can try to transplant the extras into different pots, but you risk disturbing the roots too much and killing them all!

Some gardeners will put a gentle blowing fan pointed at their sprouts for a few minutes each day for vigorous sprouts. This helps the main stem grow stronger and less prone to breaking.

Repotting and Transplanting
In order to take up all the hydration they require, tomatoes develop some extensive root systems! They will often outgrow their initial pot in the span of just 6 weeks. Sometimes less they are treated to a post-sprout root stimulant (Triple-Super Phosphate is a favorite). Keep an eye on the hydration needs of your little sprout, and if it seems like they are blazing through their water in less than a day, you may want to look into getting a new pot and soil for the little guys! If you plan on growing your tomatoes in pots, you'll want to get at least a 3-gallon pot per plant. You must transfer those tomatoes to a location similar or even better to the environment they're already growing in. 

If you're transferring them to a raised bed or directly into the ground, select a soil amendment that is rich in organic matter. If you're transferring them to another pot, select a soil that is specifically for container gardening. DO NOT USE GARDEN SOIL IN POTS CONTAINERS! Wait to transplant your tomato seedlings into the garden until after the average last spring frost date.

Once the sprouts have been transplanted into their forever homes, you'll want to give them some support, whether it be a standard tomato cage, a tomato ladder, or a homemade support system. This will help keep the branches from breaking and keep the fruit off the ground. 

When transplanting into new pot or into the ground, plant the main stem an extra few inches into the soil. This will help give the sprout more support, and will produce more roots!

Thinning out your tomato foliage:

Tomatoes have incredibly dense foliage, which is terrific for energy production, but terrible when it comes to providing bugs a place to hide! These biting bugs (especially outdoors) can devastate your little plant in a matter of hours. When your tomato plant is nice and bushy, it's a great idea to thin the foliage out by at least 1⁄4, which opens up the plant and allows sunlight to hit inner leaves. This will also reduce the likelihood of other diseases developing in damp, under-leaf areas. 


Troubleshooting Your Sick Tomato Plant:
Your tomato leaves can tell you a lot about what's going on with your plant and if you need to adjust the nutrients in the soil. In general, they are pretty carefree as a plant, but if their soil is slightly out of whack, they will complain a lot! By monitoring their foliage for signs of stress, you'll be ahead of the game and be able to apply a cure before the plant is even able to stress that much!

Of course, if you have any questions or need any help with your tomato sprouts, send us an email at We are always happy to help!

Happy 'Mater Growing!


Our 4-variety Tomato Seed Starter Kit comes with everything you need to get started, seeds, pots, soil, markers, and a basic instruction manual, while our 8-variety Tomato Garden Seed Set just comes with the seeds and plant markers. 

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