Home » Tomato seeds not germinating (8 Possible Reasons)

Tomato seeds not germinating (8 Possible Reasons)

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 not germinating

  1. Planted to deep
  2. Old Seeds
  3. Not stored properly
  4. Over-watering
  5. Under-watering
  6. Soil temperature below 50° F or over 95° F
  7. Not enough time has elapsed
  8. Fungus and bacteria

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.

#1 Seeds Planted Too Deep

One reason your tomato seeds not germinating is they were planted 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.

#2 Seeds Are Old (tomato seeds not germinating)

If you store your tomato seeds in a jar inside the refrigerator, the 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?

#1 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.

#2 Paper Towel Test

  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 the germination rate

Once you determine your germination rates 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.

Get started with your survival garden. Read the Ready Squirrel article, Survival Garden: Best Plants to Grow

#3: Seeds Stored Improperly 

Another reason your tomato seeds are not germinating is improper storage. 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 zip-lock bag. (seeds should be dry before going into the container, or moisture will be trapped inside, and fungus or bacteria could grow)
  • For short-term storage, you can make your own seed packets from paper, 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 the type and variety of seed and the date of harvest

#4 Watering Too Much (tomato seeds not germinating)

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

If the soil is soggy, too much water. This 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 remove the fungus, use less water and sprinkle powdered cinnamon on the soil’s surface. I recently did this with English Lavender seedlings, and it worked well.

#5 Not Watering Enough

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

#6: Soil Temperature Too Hot or Cold

The optimum temperature for starting tomato seeds is 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

#7 Not enough time (tomato seeds not germinating)

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 luck starting tomato seeds in seedling trays with a clear plastic cover.

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

#8: Fungus or Bacteria Are Present (tomato seeds not germinating)

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

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, or the seedling will come up but become mushy and wilted.

Scott, Ready Squirrel

How to Sterilize 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 them immediately

Use Sterile Soil For Starting Tomato Seeds

For sure you want to use sterile soil to start tomato seeds because this will give them the best chance of success. Also, 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.

Scott, Ready Squirrel

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

Up next, is how to sterilize the soil.

6 Steps to Sterilize 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

Finally, harvest your own tomato seeds.

Harvesting Tomato Seeds

Consider harvesting your own seeds to ensure you have a quality seed with good germination rates by saving 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.

Scott, Ready Squirrel

14 Steps to harvesting tomato seeds

  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 date of harvest
  6. Place the lid on the jar
  7. Leave the seeds in the jar for 2 to 5 days
  8. The seeds will begin fermenting, breaking down the seed coating, and killing unwanted bacteria and fungi.
  9. After 2 to 5 days, skim the pulp off of 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 freshly grown tomatoes.

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