Starting Tomatoes From Seeds
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Tomatoes are an incredibly rewarding crop to grow! Just one plant can provide a garden with unmatched beauty and ENORMOUS amounts of food. Being a warm season crop, tomato seedlings and plants need to be protected from freezing temperatures and harsh weather conditions to grow, thrive and survive. For this reason, we start tomato seeds indoors and do not plant them outside until the threat of frost in our area has passed.
Temperatures 32°F and below can easily kill or severely damage a tomato plant. Optimal temperatures for tomatoes to thrive range between 65-95°F, but plants can tolerate temperatures that are higher and lower then this range for increments of time. Consistently high or low temps are detrimental to the plants over-all performance and can cause a multitude of problems.
To set yourself up for a successful tomato growing season, start your seeds indoors or in a protected and controlled environment. Sufficient light, quality potting soil, and warmth are crucial to being successful! Starting seeds before the last threat of frost has passed will allow you to have strong, established seedlings that are ready to go in the ground when the temperatures have warmed, giving a major head start on the season and supporting a much earlier harvest. Getting this head start is especially important for gardeners with shorter seasons or for gardeners striving to grow tomato varieties that require more days to reach maturity.
We will go more into the details of early, mid and late season varieties in a separate blog, but do be mindful of the amount of days a specific variety requires to mature and the amount of frost free days your climate actually provides. You can then plan accordingly and prevent putting efforts into a plant that will die from the fall/winter freeze before any tomatoes have even been harvested. Tomatoes typically take 60-100 days from transplant to mature and produce fruit, depending on the variety and growing conditions.
WHEN DO I PLANT MY TOMATO SEEDS?
You will want to start your tomatoes seeds 6-9 weeks prior to your climate's average last frost. As seedlings become established and temperatures warm, you will want to harden them off (more on this below) and plant them outside after the threat of frost has passed and weather conditions are mild.
EXAMPLE OF WHEN TO PLANT TOMATO SEEDS:
Average last frost date for zone 6b: June 1
(Calculate 6-9 weeks prior to June 1)
Seeds should be started sometime between: March 30 - April 16 (6-9 weeks prior to June 1)
HOW TO FIND OUT MY AVERAGE LAST FROST ?
To find out your climate's average last frost date and acquire your regions Agriculture Grow Zone (along with high and low temperatures, season length, last frost date, etc.), enter your zip code in the USDA Plant Hardiness Zone Map generator here: https://garden.org/nga/zipzone/
WHEN DO I PLANT OTHER VEGETABLE SEEDS?
For dates on when to plant different garden seeds in your specific grow zone, generate a planting calendar specific to your climate, by entering your zip code here:
There are many alternative methods to sowing seeds - such as different planting containers, different soil mediums, different ways to label, etc. Over time you will find what fits your needs best.
Below is a step-by-step guide that can be tailored to your preferences.
BASIC SEED STARTING SUPPLIES:
For some of our favorite seed starting supplies visit our Amazon Shop.
How to get started:
Add a few cups of lukewarm water and mix well, removing any large twigs and breaking down chunks of mix at this time. The mix should be evenly damp but not soggy wet.
Fill your seed cells to the top with soil and gently press down to ensure there are no air pockets in the bottom of the cells. After pressing the soil down gently and topping off where necessary, there should be about a 1/4 inch of room at the top of each cell.
Use a pencil to poke 2-3 small holes, side by side, near the center of each cell. The holes should be shallower than the depth of a pencil’s eraser, just under an 1/8 of an inch deep each.
Plant 1 seed in each hole, totaling 2-3 seeds per cell, to ensure germination.
Cover gently, making sure all sides of the seed has come into contact with the soil.
Label and date each pot promptly as it can be very easy to forget what was planted. Tomato seeds can take anywhere from 4 -14 days to germinate...all varieties are different.
Fill the drainage tray / water reservoir so that your pots sit in with 1/4 - 1/2 inch of lukewarm water. You want to allow your seedlings to soak up water from the base of the pots like a sponge, rather than pouring water into the soil, which can potentially dislodge your seeds. Watering from the base can establish a stronger root system, prevent dampening off, and the surface soil will remain dryer preventing fungus gnats.
Cover with a dome or use plastic wrap or a clear plastic bag. This will help retain moisture, warmth and speed up germination. Note* Remove the covering a couple of times each day to offer air flow and to prevent algae growth, mold and dampening off.
Place your entire set-up on top of a heat mat or warm surface or at least keep it in a room that stays between 70 - 85° Fahrenheit.
At the first signs of life, remove the dome or plastic bag promptly, even if only a few seedlings have emerged. At this time, you can also remove the heat mat, but make sure to keep the room itself heated. Side note: The other seedlings will follow shortly if you are keeping the soil moist and the environment warm. Over the next two weeks, if multiple seeds have germinated, you can pinch out the weaker sprouts, cut them at the base with scissors or choose to separate the seedlings (also known as “pricking out“).
Then pop them out of the seed cell and gently detangle the roots. It is important to do as minimal damage to the stem and root system as possible. Replant quickly into a new pot with prepared potting soil. Stout, strong stemmed seedlings with large cotyledons (first set of leaves) are choice contenders to grow.
Immediately provide light to your seedlings at first signs of life. Place the light directly above your seedlings, as close as possible, without damaging your plants. Keep in mind that if your light emits high heat, they should be distanced further to prevent burning the sensitive seedlings or drying the soil out too quickly. Watch very closely for the first few hours to see how the seedlings and soil react. If the soil dries up right away, the light may be too close. If the plants are reaching upward, the light is too far. The goal is to keep your lights close enough so they support your plants growing stout and strong, instead of leggy and weak.
The hours of light you provide to your seedlings is a personal preference but it is best to offer approximately 14 hours a day at minimum if possible.
Once your seedlings have begun to sprout and are placed under the light, you will turn your fan on low and have it rotate back and forth. It should offer a light breeze, good airflow and gently vibrate the seedlings as they grow. This not only provides airflow and can help prevent dampening off, but also encourages the plants to root deeper, promoting stronger and hardier plants.
Check the moisture of your soil daily. Tomatoes do better in soil that is damp to somewhat dry versus overly wet. Practice a consistent watering schedule by pouring about a 1/2 inch of water into the reservoir that your seed trays sit in when the soil begins to dry. Additionally, mist the the top layer of the soil while your seedlings are germinating to help them emerge from their seed casing. Refrain from pouring water into the soil until your seedlings are larger and have strong root systems.
Your plants will first produce cotyledons, which are the first leaves to emerge on a seedling. After approximately 2 weeks, you will see their first set of TRUE LEAVES emerge, which will look like tomato plant leaves. Some choose to feed their tomato plants immediately after germination, but I prefer to feed after the first true leaves have emerged. It is recommended to mix an all purpose, water-soluble fertilizer at half the recommended strength and feed the seedlings 1-2 times a week simply by pouring it into the reservoir in place of your normal watering.
After around 4 weeks, when your plants are on their second set of true leaves, you will want to plant them into larger containers.
Have fun and enjoy the process. Growing your own food will reward you in many wonderful ways!