Tomato Seeds Not Germinating: 8 Possible Reasons


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Why Prepping Is Not A Waste Of Time

So your tomato seeds didn’t germinate. You started out optimistic, even excited, to plant your first tomato seeds and then nothing. They never sprouted. Look over the following list to see if you can figure out why your seeds aren’t sprouting and then give it another try.

8 Reasons Tomato Seeds Don’t Germinate:

  1. Seeds are planted too deep
  2. Seeds are old and not-viable
  3. Seeds were not stored properly
  4. Over-watering
  5. Under-watering
  6. Soil temperature is below 50° F or over 95° F
  7. Seeds haven’t been in the soil long enough to germinate
  8. Fungus and bacteria
  9. BONUS: How to harvest your own viable tomato seeds

I have purchased seed packets that didn’t germinate well.  Even newly purchased seeds can be unviable. Check out reviews before purchasing seeds online; buyers will post if germination rates are poor and other drawbacks to specific varieties.

Germination: the development of a plant from seed after a period of dormancy.

Reason One: Seeds Planted Too Deep

Don’t plant your tomato seeds more than 1/8″ deep.

Plant tomato seeds much more than 1/8″ and the seed may not have enough energy to push through the soil.

A general rule of planting depth for seeds is twice or three times as deep as the seed is wide. It can be tricky to get this just right. If in doubt err on the side of planting tomato seeds too shallow.

Reason 2: Seeds Are Old

If you store your tomato seeds in a jar, inside the refrigerator, seeds will last a year.

There are examples of tomato seeds lasting 16 years or longer, but this is rare. Tomato seeds often last 4 to 5 years if properly stored, but the germination rates will decline over time.  

If you’ve gone to the trouble of setting up a garden bed for tomatoes, I would use the freshest seed you can get.

How Can I Tell If My Tomato Seeds Are Viable?

Method 1: The Float Test

  1. Place your tomato seeds in a container filled with water
  2. Let seeds sit in the water for 15 minutes
  3. Seeds that float are not viable.

Method 2: Paper Towel and Ziplock Baggy Method

  1. Wet a paper towel (thoroughly moist, but not dripping) A good way to moisten the paper towel is with a spray bottle.
  2. Evenly space 10 seeds on 1/2 of the damp paper towel (10 seeds makes it easy to determine germination rates)
  3. Fold the unused 1/2 of paper towel over the seeded half
  4. Carefully place the paper towel in the 1-gallon ziplock bag
  5. Seal the top of the bag
  6. Keep the bag in a warm, dark place like a desk drawer or a cupboard
  7. Check the bag daily to make sure it’s still moist, moisten if necessary
  8. Tomato seeds should sprout in 6 to 14 days telling you if the seeds are viable and giving an estimate of germination rate

Once you determine your germination rates, it will help you decide if you want to plant more seeds to get the number of tomato plants you need or to get new seeds.

Reason 3: Stored Improperly 

Once you find tomatoes that do well in your location consider saving seeds and storing them. Storing your seeds properly will add to their longevity and viability.

  • Store seeds in an airtight container: like a baby food jar, canning jar, or a zip-lock bag. (seeds should be dry before going into the container or moisture will be trapped inside and fungus or bacteria could grow)
  • You can make your own seed packets from paper for short-term storage, but paper won’t protect seeds from humidity.
  • Store in a cool, dry, dark location like a pantry
  • Store with a desiccant like silica gel, if possible 
  • The refrigerator is the perfect place to store seeds. An ideal storage environment is below 50° F with less than 50% humidity. Avoid storing seeds in a warm, humid environment like a greenhouse
  • Mark storage containers with type and variety of seed, and the date of harvest

Reason 4: Too Much Water

I tend to over-water my seeds. It can be tough to get watering just right. Your goal when watering your tomato seeds is to keep the soil moist or damp. There are two signs you may be watering too much.

If soil is soggy, you are giving your seeds too much water, which can rot seeds and young roots.

Another sign of overwatering is white fuzzy growth on top of your soil. This growth is a fungus. To get rid of the fungus, water less and sprinkle powdered cinnamon on the soil’s surface. I recently did this with English Lavender seedlings and it worked well.

Reason 5: Under-watering

If your planting soil is dry to the touch, you are under-watering your seeds. Seeds need a moist environment to germinate

Reason 6: Soil Temperature

The optimum temperature for starting tomato seeds is between 68° – 86° Fahrenheit

If you Start your tomatoes at soil temps of less than 50° F or Higher than 95° F and they won’t germinate.

Minimum °FOptimum Range °FMaximum °F
50°68° to 86°95°
Source: California Master Gardener Handbook, 2nd edition

Reason 7: Time

Soil-Temp32ºF 41ºF50ºF59º F68ºF 77ºF86ºF95ºF104ºF
Days to Sprout43 Days14 Days 8 Days 6 Days 6 Days10 Days
Sources: Department of Vegetable Crops, University of California, Davis
little or no germination

I’ve had good luck starting tomato seeds in seedling trays with a clear plastic cover.

As long as the room is somewhat comfortable, you don’t need a seedling heat mat or any unique gizmos. Once the seeds sprout, take the cover off and place the seedlings in direct sunlight or under a plant-light.

Reason 8: Fungus and Bacteria

Sterilize whatever seedling containers you are using to plant your tomato seeds. Disinfecting isn’t necessary if the planter is new.

Sterilize planting tools too.

Note: Damping-off is a disease that commonly affects seedlings started in dirty pots or from overwatering. Fungus in the soil can rot the seed or the roots of the little seedling. The seed may rot and or the seedling will come up but will become mushy and wilted.

How Do You Sterilize Your Seedling Trays and Tools?

  1. Pre-wash your pots, trays, and planting tools with water and ordinary dish soap
  2. Create a 10% bleach solution in a bucket
  3. Soak planting vessels and tools in a 10% bleach solution for 10 minutes
  4. Air dry
  5. Store containers in a clean garbage bag if you aren’t using immediately

Should I Use Sterile Soil For Starting Tomato Seeds?

Yes, use sterile soil to start tomato seeds.

This gives you the best chance of success. There are commercial mixes available specifically designed for seed starting.

I use a commercial seed-starting mix so I don’t have to worry about my seedlings getting sick, or the messy task of sterilizing my garden soil.

Commerical starting mixes undergo treatment to kill pathogens and any seeds that might be present in the soil. Sterilization cuts out competition from other seeds and kills pathogens to minimize the possibility of damping-off.

How Do You Sterilize Your Planting Soil?

  1. Preheat your oven to 200° F
  2. Place 6″ of soil in an oven-safe dish or pan
  3. Cover with tin-foil
  4. Determine when the soil reaches 200° F (Use a cooking thermometer)
  5. When the soil reaches 200° F, Bake for 30 Minutes
  6. Let soil cool to room temperature before using

Bonus: Harvesting Tomato Seeds?

To ensure you have a quality seed with good germination rates, consider harvesting your own seeds.

Save seeds from the healthiest most vibrant plants.

Only save seeds from traditional open-pollinated tomatoes, also known as heirloom varieties. F-1 Hybrids won’t regrow as the same tomato.

  1. Choose two, fully ripe tomatoes (Approximately 200 Seeds)
  2. Cut the tomatoes in half
  3. Squeeze the seed containing pulp from inside the tomatoes into a lidded ball jar
  4. Fill the jar 1/2 way full with water
  5. Mark the jar with the name, variety, and the date of harvest
  6. Place the lid on the jar
  7. Leave the seeds in the jar 2 to 5 days
  8. The seeds will begin fermenting which will break down the seed coating and kill unwanted bacteria and fungi
  9. After 2 to 5 days skim the pulp off the top from inside the jar
  10. Transfer seeds to a fine mesh strainer and clean seeds with fresh water
  11. Remove the gooey gel around the tomato seeds. It inhibits seed growth
  12. Place seeds somewhere they can dry out, like on a paper towel in the kitchen window
  13. It takes 2 to 3 weeks for tomato seeds to dry out
  14. Store your seeds

Good luck and don’t give up. You deserve to eat fresh grown tomatoes.

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