Seeds Not Germinating? 12 Reasons Why and How to Fix It

If I told you I’d never had problems with seeds not germinating, I’d be lying. There is a learning curve in sowing seeds. The seed germination process is fraught with potential problems that beginners often encounter.

I’m here to address those potential problems. Sometimes its conditions present during seed germination, such as the growing medium, and sometimes it’s the seeds themselves. Sometimes you get everything right, but some external force ruins the process. 

Don’t lament if you’re dealing with problems when you are planting seeds for the upcoming season. Let’s learn about starting seeds in conditions that will contribute directly to your success in the growing season. 

Germination Conditions Need Adjustment

The conditions in which seeds are started have a direct impact on the rate of germination. Make little adjustments as needed and you’ll easily sprout seeds into plants. 

Light

Not all seeds need light to germinate, but some do. Some seeds get the best lighting from direct sunlight, but that’s not always available when you’re starting seeds indoors. Research the species you’re growing to determine optimal light conditions, so certain seeds don’t remain dormant while others germinate.

Issues with lack of sunlight can be reconciled with a grow light. Grow lights are particularly important if you’re sowing seeds indoors. Without light, many species will struggle soon after sprouting.

Temperature

Incorrect temperature is often the culprit for problems with seed starting – especially when you’re starting seeds indoors.

The vast majority of seeds need a soil temperature between 65°F and 85°F (18-29°C). While that might be the temperature inside your house, if your setup is near a drafty window, the seeds may not get the warmth they need. An arctic blast with extreme temperatures could prevent those winter-sown seeds from breaking dormancy.

Use a soil thermometer to determine whether or not you’ll need some extra assistance in the form of a plastic tub or container over your winter seeds (if winter sowing), or a heating mat under seed trays. Sometimes a grow light is enough to warm up a cold soil temperature and help seeds break dormancy. 

Moisture

Directly related to temperature and light is the moisture content of your seed starting operation.

Most seeds need a generous amount of water to sprout. Large particulates in your soil reduce moisture against the seed itself, so consider this when sprouting seeds (especially in well-mulched raised beds).

Think about whether or not your seeds prefer more or less moisture. Reduce watering if you realize your soil doesn’t need to be as wet, and you’re still within the germination period for certain seeds. For instance, instead of saturating, try a spray bottle to mist the soil surface. 

In some instances, you might not be watering enough. Certain seedlings require lots of moisture for the seed coat to yield to the dicots within. Constant drying out of your starting mix could have to do with the media, the ambient temperature, and humidity, or with the watering frequency.

To germinate, all seeds need adequate moisture. Some need more than you think. Soybeans, for instance, need a moisture content of at least 25% in the soil to sprout seedlings. Measure the moisture content in the soil with a soil meter. If you find you’re consistently having issues with moisture and humidity, a grow tent can make conditions optimal for germination.  

Soil or Germination Medium

The type of media you use feeds directly into the amount of oxygen making its way to your vegetable seeds. If there’s an excess of clay in the growing medium, there may not be enough oxygen and water moving through to start seeds.

If you find there is no drainage in the media, amend the soil and start again. Usually, remediation of this kind is possible with quick seed germination, and not as easy for slow seed germination.

Seed germination is also contingent on how deep you plant the seeds. Planting depths are generally on seed packets, so follow the guidelines there to determine how deep to plant in your growing medium. Some seeds don’t need much more than being spread on the soil’s surface. 

You might have a leftover starting mix that just isn’t suited to get your seeds germinated. By the time you’ve planted and waited, nothing happens and it’s too late to make changes. Research the specific species to determine the perfect germination method.

For example, some do best when they’re germinated in a plastic bag with a folded towel soaked in water. Plants like chia enjoy clay as a starting medium. In this case, too much organic material prevents chia sprouts. By paying attention to the needs of your seeds, you’ll have young seedlings in no time. 

Timing

Even if you start seeds indoors, you’ll stunt them if you plant them at the wrong time. Light, temperature, and humidity change indoors and outdoors when seasons change. If you plant before the last frost, a drastic temperature shift can kill seeds. One way to boost your ability to successfully produce seedlings is to plant at the right time.

Your HVAC system has different habits in different seasons, too. Maybe you placed your seed packet pre-sprout next to the HVAC outflow and they got too dry and hot to survive. The same goes for your seed trays. You may have neglected them at a window that got too cold based on temperature fluctuations.

Regular watering is important, especially in seasons where day and night temperatures vary greatly. But too much water rots seeds before they have a chance to sprout. Use organization tools like a calendar or a spreadsheet.

Seed-Related Germination Issues

Sometimes the conditions in which the seed is planted aren’t the only culprits for improper seed starting. Seed quality, type, and needs for growth have an impact as well. 

Cold-Stratification

Cold-stratification is needed for seeds that require cold hours to start. Wildflowers are a common example.

For instance, milkweed seeds naturally in fall and sprout again in spring. If you’ve accidentally planted seeds that need cold hours before it’s time, try again one of two ways. First, seed outdoors in fall, allowing the natural process of cold stratification to take place. Alternatively, put the seeds in the freezer for a time and then continue growing indoors ahead of the transplant in your garden.

Some need two weeks of cold, and some need two months. Check your local agricultural extension office or reputable gardening source to learn what period of cold is needed. 

Scarification

Maybe you’ve had some nasturtiums you just can’t get going. You’ve tried year after year, changing soil blends and tinkering with conditions. What you might be missing is a mechanical process called scarification.

By scratching the seed coat, you break open the seed, speeding up the sprouting process. If your larger seeds aren’t germinating, check to see if they need a slice or two to germinate.

Seed-borne Illness

Seed-borne illness result from improper seed saving and improper environmental conditions in seed storage. Sometimes white mold can form in the fermentation process when saving tomato seeds. Sometimes the distributor isn’t reliable, and you get moisture levels in transit that promote infections that could transfer to your garden.

Most good-quality seeds and their distributors won’t have disease issues. Use online reviews to determine whether or not a purchase is a good idea for smaller companies. Be cautious of imported seed, as it may not be what you ordered.

Seed Storage

If you have old seeds, check to see if they’re beyond their storage life before you plant them. Seeds that are too old should be replaced with more seeds, instead of planted. Some seeds have a two-year shelf life, other seeds have a five-year shelf life.

Seed packets will have expiration dates that tell you if planting is a good idea. Some seeds only have a shelf life of several weeks. If you don’t have the information on hand research to find out. 

Seed can be stored improperly too. Certain plants do not like to be stored in cold temperatures or even room temperature sometimes.

Another issue in seed saving is ambient humidity. Higher humidity promotes mold that could damage seed, or fungal growth that could be transmitted into your garden when you plant seedlings. In this case, the plant may have germinated, but some disease is present which eliminates seedlings. How you store seeds has a bearing on germination. 

Germination Rate and Time

Some plants make tiny seeds that have a very low germination rate. Other plants are easy and notorious for sprouting 100% of the time (sunflowers, anyone?).

Before you plan your garden, think about the germination rate. Sow those with a lower rate at a higher frequency per hole. Those with a higher rate can usually go right into the garden.

There are also times when seeds take a long time to germinate. Many herbs take months before they’re ready for transplant in a garden. Check germination rates and times before giving up. 

External Germination Problems

Then, there are your favorite friends in the garden who love snacks. Let’s talk about them and a few other pesky pals. 

Hungry Wildlife and Pests

Some plants are desirable to deer, birds, squirrels, and mice among others. Even if you broadcast sow, you might find they think the sprouts or the seeds themselves are a buffet.

If you’re going to broadcast seeds, protect each seed or sprout with a barrier. This could be chicken wire around the garden bed or a shade cloth that keeps out any pest that could reach them from above.

Another external but underground issue that could arise is grubs and worms that like to have a chomp on the roots of new sprouts. Treat the soil ahead of time with nematodes to lessen the threat. Alternately, plant these types of crops in containers where grubs and other larvae can’t get them. 

Diseases

When you plant seeds in used soil, whether outdoors or indoors, soil-borne illnesses are a risk. These include damping off which is caused by one form of soil-borne fungi. Affected seedlings grow on spindly stems and don’t root deeply enough, and they often break off at the soil level and die.

Another thing to look out for is bacterial infections that present similarly to damping off. Just like damping off, they attack after the seed has germinated, making it seem like things are going ok at first, but then your seedlings die in a few weeks.

Soil tests through your local extension office can determine if bacterial and fungal infections are present in a garden bed. Check for damping-off especially in cool wet seasons before you plant. 

Frequently Asked Questions