Seed Starting: Tomato Edition

Posted By on February 5, 2015


Seed starting might seem like a momentous task for some people. If you haven’t done it before you might be unsure of yourself. So, we’re here to talk you through a few options and techniques we’ve learned in the past few years. We’ll start out with a bit about the supplies you’ll be using, method of planting, and continual care for your seedling plants.



Seed Starting Mix
You can find this at most stores where seed is sold or you can make your own from home. Whichever you do, it is wise to wet the mix in a bucket before you plant so that water will easily absorb in the future and to cut down on the dust.

Homemade Mix:
4 Parts Finely Sieved Compost
1 Part Perlite
1 Part Vermiculite
2 Parts Coir or Leaf Mold
*Leaf mold is simply broken down leaves that will help retain moisture in your mix. It takes roughly a year to break down for use, but is another FREE additive for your garden

It is really up to you what you’d like to use to plant your seeds in, but be sure there are drainage holes. There are many options out there from trays, cells, to homemade. Use what you’re comfortable with or experiment!

Trays provide an ease to the seed starting business. Space is saved by allowing you to start many seeds and/or varieties in a flat which can be pricked out and potted up later. This is especially useful when germination rate is in question. It also saves time with preparing the containers. You only need to fill one large container as opposed to filling up many small cells or homemade planters.

Cells are another option to start seeds in. The beauty of cells is that they give each seedling its own growing space. They can grow longer before being potted up and produce a larger root system. They’re easy to use and ad order to your seed starting regime.

Homemade containers are the final option you half. Using egg cartons, toilet paper rolls, and newspaper are all easy to use plantable pots. However, they do disintegrate easily with excess water. You can also choose to save used (and cleaned) dairy containers. These could be anything from yogurt to milk cartons. Use your imagination! Just be sure to poke holes in the bottom for drainage.

There really isn’t a whole lot to say about what KIND of water you are using. Rather, it’s how you use it that matters. Watering seedlings is a little different than going out to water in the garden. We suggest that you water from below. Remember those drainage holes? This is another place the come in handy. Set your planted container in a couple inches of water and let it sit until you can see that the soil is evenly moist across the container. The reason for watering this way is so that it makes seedling’s roots grow downward, looking for water, and creating a larger root system.

One thing to keep in mind with tomato seedlings is that they sometimes start getting a purple tint to the underside of their leaves and stems. This is a sign that they are not getting enough phosphorous. The reasons could either be rusty water or they have depleted the nutrition in their soil. You can solve the problem two ways. Pot the plants up in a larger container with new soil or feed them a bit of phosphorous when you water.

Light is not always important to germinate seeds, but once they burst forth into the world they really do need it. If you have a heated greenhouse or sunny south facing windows you can set your seedlings there. Your seedlings may stretch a bit with the shorter daylight hours, but don’t worry too much about it. If they get too leggy, you can always pot them up into a deeper container.

We suggest to use a high power florescent light for the best results.

Tomatoes need warm soil for germination. A soil temperature of 70-80 degrees is sufficient. The sunny window you use might be okay, but if not set the container on a radiator or heat mat. If it is cooler, seeds will take longer or might not germinate.

This is the fun part! There is a wide variety of tomatoes you can choose from in all sorts of colors and shapes. Pick your favorites and try something new each year! You can find a nice variety of tomato seeds in our Seed Shop.

All in all, the best advice we can give you is to experiment. What the ‘experts’ say (and even us) just might not work for you. Find what fits your lifestyle and go with it. Now that you’ve made all your important decisions, it’s time to plant!


1. Prepare container and soil.
2. Use a dibber or pencil to make a small hole 1/4 inch deep in soil.
3. Drop seed into hole and carefully cover in the hole with soil.
4. Cover container and set in a warm place to germinate.

Sowing Time
To get good sized tomato plants for planting out, you’ll want to start your seed 6-8 weeks before the last frost date. Don’t know what that is? You can find your average last spring frost date HERE.

Germination is the time it takes for the seedling to awaken from dormancy and start growing. This generally takes 6-10 days to happen, but depending on the viability of your seed and the variety it may be more or less. You’ll see little green plants with two leaves popping out of the soil indication that the seed you sowed has germinated. The two leaves present at this time are called ‘cotyledon’ or seed leaves. Later on you’ll see a set of new leaves form in between the cotyledons that will look more familiar to the types of leaves you are used to.

Potting On
Potting on is simply transplanting the young plant into a larger container that will provide for a larger, stronger plant. If starting in trays you will do this as well as if the plant has outgrown its container. To pot on you will need to gently prick out/remove plant from its container. Hold it gently by a leaf so you will not damage the stem or roots. Plant a little deeper than it was in the previous container, but be sure leaves do not touch the soil. Fill in any of the remaining hole and water.

Hardening Off
Once your plant is large enough to plant outside you will need to start ‘hardening it off.’ It has been grown inside its whole life so far, so think of this process as toughening it up until it is ready to face all the elements.

To do this, you will start by placing your plants outside in a partly shady area for half an our. Continue to do so every day for a couple weeks. Every few days add another half hour to the time outside and slowly expose them to more light. By the end of the process you should be able to keep your young tomato plants outside indefinitely, in full sun. You are now ready to plant them in the garden, provided the last frost date has passed.

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