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How to Start Tomato and Pepper Seedlings – Guest Post

Updated: Jun 9, 2021

By guest contributor Nicole Tautges

We all love to watch our green tomatoes turn red and to pick fresh hot peppers in August. Both tomato and pepper plants, when well cared for, yield lots of tasty fruit for canning, pickling, and salsa eating in the hot days of summer. However, to get great fruit at the end of the season, it has to get off to a good start!

Tomato and pepper plants cannot be directly sown into the soil in the spring except in very warm climes, something that the Palouse is generally not known for. Both require high soil temperatures for seeds to germinate and growth is slow under cool conditions, unlike other garden vegetables that thrive in cooler spring temperatures like broccoli and spinach. Consequently, we must give tomato and pepper plants a head start in the spring by starting them indoors with enough time to grow large enough to survive the transplant to the garden and then to bear fruit by the end of the hot weather, which on the Palouse is around the end of August. Now one could buy tomato and pepper plants in May at $2 or $3 apiece, simply transplant them into a garden or planter pot around Memorial Day, and then pick and enjoy the fruit in a few months (after, of course, judicious watering). Or, in the era of DIY, you can get ahead of the cold weather by starting your tomatoes and peppers in your own home.

Containers and “soil” –

While starting tomato and pepper seeds doesn’t require fancy equipment, there are a few important things to consider when creating a favorable environment for the seeds to germinate. The first choice you need to make is what kind of pot to use. Many hardware stores display seed start kits usually offered by the Jiffy Pot company that include small peat pellets with starter media, which is a loose mixture of plant fibers that provide the nutrients that seeds need to germinate and grow. These are small, easy to plant, and easy to store, and may be a good choice if space is limited. A drawback to using these pellets is that if plants grow taller than a few inches before transplanting outside, then the fibrous media in the pellets is not strong enough to support the weight of the stem and leaves, and seedlings will get floppy. Another drawback is that these pellets must be monitored closely for water, as water evaporates easily from the plant fibers and plants dry out fast, especially if you are using a heating mat. Alternatively, there are a number of peat pots, or cardboard pots (also offered by Jiffy and available in most hardware stores), that are small and biodegradable, so you could start seedlings in these and then put the whole pot in the ground when you transplant the plants outside. I have found these to be superior to the peat pellets, as they are deep enough for the seedlings to develop a healthy root system, hold more water in the soil or media, provide more support to the plant, and are very affordable. The only drawbacks with peat pots are that they get fragile after several days of watering and can rip or disintegrate in some parts, allowing the soil to fall out of the pot. Conversely, when planted outside, they do not necessarily biodegrade by the end of the season, and I have found them relatively intact when turning the garden soil over the next year. However, they do biodegrade eventually, and if soil is shoveled over them they will break down quickly. Personally, I have switched to using black plastic four- or six-cell inserts in a hole-less black plastic tray, like the ones used in greenhouses. Make sure to get the hole-less trays, as filling the trays with water, rather than watering the seedlings over the top, will result in them developing a stronger root system. While plastic is of course not biodegradable, they are quite durable and handling them carefully, I have used the same inserts for several years. As for growth media, there are many options out there. If you have worm castings or compost lying around, you could use that as growth media. Normal potting soil works well, as does the loose “start mix” that many hardware stores or nurseries sell. Some people just use soil from their garden. Choose what works best for you.


Choosing a light source is very important, as all plants require more intense light than our normal house lighting provides. I suggest T5 fluorescent lights in a fixture, which are sold by many vendors, online and in-store (local hardware stores sell fixtures and the bulbs). One bulb is affordable and multiple bulbs can be fitted into a fixture to increase lighting intensity, if necessary. With limited funds you may have to make decisions regarding what to spend money on, I suggest you give lighting high priority, compared to the other materials. If you have a small shelf or only one tray (trays are generally 20 x 10 inches), 1 T5 bulb should be sufficient; however, if you are lighting a larger shelf or area, I suggest you get a fixture that fits multiple T5 bulbs, or get a more intense light source. You can tell if plants are not receiving enough light if they grow long, spindly stems that don’t seem stiff enough to support their own weight. If this happens move the seedlings closer to the light source (an upside-down tray works well), or add more lighting to your fixture. As one T5 bulb can cost from $30 to $50, depending on your budget you may need to work your way up to several lights over time. However, one 20 x 10 inch tray can fit up to 50 plants, depending on the size of pot you use, and so for the home gardener, one to two bulbs should suit your lighting needs.


Another consideration is heating your seedlings. This is optional, but can result in faster growth and more robust seedlings. Many hardware stores market heating pads to put under planter trays and warm the soil. I use these, as I have observed faster and more successful germination of pepper seeds when the soil is heated (they like it hot!). If you are a fan of the great white North like I am and you keep the house good and chilly, you will likely need to heat the soil or your pepper seeds may not germinate. These heating mats are relatively inexpensive and worth the investment (usually around $20). Disclaimer:  while heating the soil is important for these plants, if you use very peaty soil media, put a clear plastic cover over your planter tray (as is sold in many starter kits), and forget to water, you could fry your seedlings, which is very sad! Be cautious of covering seedlings with a plastic tray and using a heating mat if you have very loose media.


Lastly, where should you put your seedlings? If you have room near a sunny window, great! But you should still provide your seedlings with at least one (T5) light bulb, as the light intensity inside, even next to a sunny window, is less than outside in the shade. They can be placed anywhere as long as they are under a light source. I have a wire rack shelving unit wrapped in painter’s dropcloth plastic, leaving the top open to let air in. This traps the heat and light inside, creating a semi-greenhouse effect for your seedlings, and also  keeps out those pesky seedling-munching pets! I use Velcro strips on one side, to make an improvised door for the plastic-ed shelf.

And that’s really all there is to it! Starting your own tomatoes and peppers allows you to select exciting varieties that are not generally offered in hardware stores or even at the Farmer’s Market, and you can go ahead and explore all those heirloom tomato varieties by accessing the abundance of heirloom seed available online or at the Co-op. Other fun start ideas are tomatillos (used for making green sauce and green salsa), green chiles, and pepperoncini (great on pizza)! Also, while there is some investment cost up front, the lights and heating mats can last many years, and many pots and planter trays can be re-used for several years. So go nuts! If you want to start tomatoes and peppers for this year, be sure to get them started by the end of April, so they are big enough to be transplanted in early June. Good luck and happy starting!

Stay tuned for more articles on how to manage your seedlings once they have emerged!

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