Seed to Seed Guide: Tomatoes
by Hannah Brown
Did you know that there are over 10,000 different varieties of tomatoes? They come in several different shapes and nearly every color of the rainbow, from the classic red to zebra-striped green, lemon yellow, sunset orange, and even a few blue varieties!
Incredibly versatile, tomatoes are great to use in salads, sauces, stews, drying projects, or just eating out of your hand as you gather them. If you are up for a challenge, try beefsteaks or other large varieties. However, if you want a guaranteed chance of success, plant a couple of cherry or plum varieties in a warm sunny spot in your garden. All of the color and taste of the big kids packed into a smaller package!
Seed Starting:
When starting your Tomatoes from seed, it’s best to start them indoors for five to six weeks before planting them in the ground outdoors. In Minnesota, this means that you should sow seeds into indoor pots or trays in late February or early March.
Plant the seeds ¼th of an inch deep into sterile potting soil about ½ an inch apart. To help you estimate what this looks like, the distance between the first and second knuckle on your middle finger is approximately 1 inch. (Check yours against a ruler to ensure accuracy.)
After planting, cover the seeds with a thin layer of potting soil and moisten them with a spray bottle filled with water.
Place the seeds in a warm, bright spot either in a sunny window or positioned under a grow light placed 5 to 6 inches above the soil. (Keep in mind when germinating under a grow lamp that you will have to move the lamp upwards as the plants grow to prevent burning them. The tops of the plants should never be any closer than 4 inches away from the grow light.)
Moisten with the spray bottle or watering can whenever the top layer of soil dries out. You can check this by inserting a finger into the soil to gauge the dampness.
Optionally, you can cover the pots and trays with clear plastic to hold humidity and stretch out the time between waterings and/or place them on top of a heating mat set to between 75 to 85 degrees to encourage germination.
Under ideal conditions, the tomatoes will begin to sprout within 5-10 days of planting. The first leaves, called cotyledons, will look very different from the “true leaves” that will emerge later. This is normal, and yes, they are tomato plants!
10-14 days after planting the first true leaves will emerge.Once all true leaves have emerged, thin the seedlings by removing and discarding all but the largest, healthiest plants.
When the plants are around 5 inches tall, or about 6-8 weeks old, slowly reduce the number of times you water per week. If you have been using clear plastic wrap to hold in humidity, discard it now, if you haven't already.
As the weather gets warmer start bringing your seedling tomatoes outside during the day to “harden them off.” Place them in a warm, sunny spot outside protected from wind and wild animals for a few hours every day, gradually increasing the amount of time they spend outside over the next week or two. Tomatoes cannot tolerate frost, so bring them indoors if the daily or overnight forecast predicts below-freezing temperatures.
Transplanting:
You can transfer the seedlings into in-ground gardens or containers once the threat of frost has passed, around mid-April. Tomatoes need lots of sunlight, so find a spot in your garden that gets full sun exposure for up to 14 hours a day. Tomatoes are also “heavy feeders” meaning they need a lot of organic material or other types of fertilizer to ensure ideal growth.
Before planting, thoroughly mix in compost or manure into the base soil to provide vital nutrients and water each seedling thoroughly.
Dig a hole deep enough to bury the stem up to the first true pair of leaves, two to three feet apart from any other plants. The hairs on the stem will convert into roots when buried and give your tomato a stronger base to grow from.
At this point, you can optionally mix in a little extra tomato-specific fertilizer into the soil at the bottom of the hole. (My grandfather swore that fish heads and/or guts were the best, but commercial mixes or extracts do the job just as well.)
Gently remove the plant from its container, place it into your prepared hole, fill in the hole with the surrounding soil, and give it a good soak to water it in. Make sure to add a trellis, stake, or tomato cage to support the plant as it grows.
If you are growing tomatoes in containers, the larger the pot, the better. One plant per container is best. Five Gallon buckets with holes poked in the bottom are an excellent low-cost option. Follow the same procedure for in-ground planting, and be aware that you will likely have to feed and water container tomatoes more often than their in-ground counterparts.
Ongoing Care:
As your plants start to grow, they will need extra support. Make sure you tie or otherwise fasten the main stem of the tomato plant to its related trellis or stake to prevent it from tipping over and possible breakage. Keep in mind that the stem shall continue to grow in thickness, so don’t tie it too tight!
Because Minnesota’s growing season is so short, to encourage the growing plant to focus on fruit development instead of leaf production, some gardeners pinch off the “suckers” from the main stem of the plant. Suckers grow at the junctions between leaves and the main stem and will look like miniature versions of the main stem. You can pinch them off between your fingers if they are small enough, or cut them off with a pair of gardening shears.
You can also encourage fruit growth by feeding your tomato plants. There are several over the counter options available in gardening stores. Make sure to read the directions thoroughly before using, as too much concentrated fetilizer can burn your plants roots and leaves, stunting it’s growth.
Seed Saving:
If you want to save seeds from your ripe tomatoes, keep in mind that tomato seeds require “wet-processing.” This means that the seeds will need to ferment to produce viable seedstock. Fermentation is the process in which bacteria, yeasts, and other microorganisms act upon a substance in a way to changes it’s form. Fermentation creates many of our favorite foods from yogert and cheese to coffee and chocolate, and it’s an important part of a tomato seeds lifecycle as well.
Begin by seprating the seeds from the flesh either by scooping them out or squeezing them into a clean, dry glass jar. Don’t worry about separating seed from the watery mass that surrounds them, that material is important for the ferementaion process.
Add an equal amount of clean water to the jar once all the seeds and pulp have been extracted. Stirr vigorously to combine.
Cover with a paper towel or cheesecloth secured with string or a rubber band to keep out fruit flies and debris, and set in a warm, out of the way place, like a shady porch or back patio. (You can store them indoors, but this mixture may start to smell, so I wouldn’t recommend it.)
Leave the mixture alone to ferment from anywhere between three days up to a week. Check on it every day or so to track it’s progress. The fermentation is complete when bubbles begin to rise out of the mixture and the top of the liquid develops a skin of whitish mold.
Rinse the seeds by placing the mouth of the jar under the flow of a hose or a sink. The mold, pulp, and bad seeds will rise and be flushed out of the jar, leaving the heavier, viable seeds at the bottom of the jar
Strain the seeds into a fine mesh strainer and remove any remaining pulp. Spread seeds out on a paper plate or other surface to dry. Make sure they dry in a single layer, as clumping may cause them to rot.
Once the seeds are completly dry, place them in a envelope labeled with the variety and date of storage and store in an airtight container in a cool, dry place, like a cupboard or basement. Tomato seeds can remain viable for up to 5 years.
Check out these sources from the University of Minnesota and North Carolina State University for more information:
https://extension.umn.edu/vegetables/growing-tomatoes and
For starting with seeds and saving seeds check out our Youtube channel under growing resources for 2023!
What kinds of Tomatoes are you growing? Share with us on our Instagram or Facebook at Como Community Seed Library!