The Truth About Seed Starting Mix Shelf Life

We’ve returned to that well-known time of year that’s ideal for planting seeds! Many gardening enthusiasts frequently wonder: Why aren’t my plants thriving? What exactly does Seed Starting Mix mean? Does it require a specific seed mixture? Is investing in a seed mix cost-effective in the long term?

Starting your garden from seeds can be a fulfilling and rewarding experience, but it’s essential to know the shelf life of your seed starting mix. Proper storage in low-humidity and low-temperature regions can help extend the life of your mix, but the key ingredient to consider is peat moss. With a 1 to 2 years lifespan, keeping track of the age of your seed starting mix is crucial to ensure successful plant growth.

The ideal seed starting mix shouldn’t be excessively high in supplements because it could damage your plants. So to create the perfect starter mix, you must be pretty careful.

What is a Seed Starting Mix?

The seed-starting mix is a soil-less medium mainly used to improve the growth of plants.

It’s a better choice for starting seeds than the standard potting soil because it’s lighter and finer.

Hand holding seeds and the word seed spelt with seeds

Is the seed starting mix essential?

You might ask, why is using a seed mix necessary when you normally go ahead and plant your seeds in the garden and let them do their thing?

And, for sure, you can go ahead and plant your seeds without using the seed starting mix, but most of them will either get attacked by microbes and start dumping off, or they wouldn’t even grow. So to improve your success rates and reduce the waste of the seeds, it is a great option to go ahead and get a seed starting mix for your garden plants.

Why Good Seeds Decay

Seeds are inactive or inert, although alive and undergo processes like living beings, such as respiration; the rate is much lower than a living plant. Seeds have a definite amount of energy, and a portion keeps consuming with this respiration process.

If the seeds get moistened, germination occurs, resulting in a drastic increase in respiration and, thus, energy consumption.

Seeds must retain plentiful stored energy to sustain seedlings until they develop their first leaves and start photosynthesizing. So to save your seed and allow them to live another day, we would advise you to use a seed starting mix.

Germination in seeds and needs

Plug of soil with small seedlings

As germination has been discussed previously, let us touch on what a seed needs to grow and germinate properly.

A seed needs proper moisture, light, temperature, and oxygen to thrive. However, there may be instances that it will still revert to dormancy and lack of ‘starting’ even when given to them.

To aid you in understanding the germination process and the basic needs for seed growth and care, I have written an article on what seeds need, their germination, and their light considerations. It recounts the conditions of a seed, the several steps in germination that you can look into, possible reasons for seed dormancy, and the reasons and maybe even possible benefits for this occurrence.

Damping-off in seeds

In line with the talk of saving seeds and probable changes in them, we would like to introduce the possibility of your seeds damping off.

Damping-off causes failed seed germination due to the humid and cold environments of the seeds. To aid with this, look into my recent article on preventing seedling damping-off. This covers the symptoms one can spot in damping-off (one sample symp[tom being the stems growing thin and fibrous), the reasons behind it, and tutorials on how to solve this problem.

Determining the shelf life of seeds

You can determine the shelf life of seeds by these steps:

  • The amount of stored energy
  • The amount of energy used during storage
  • Also, the amount of energy needed from germination to leaf development.

With these, let us look into optimal conditions for storing the seed mixes.

Optimal Conditions for Starter Seed Mix Storage

Optimal conditions are used very frequently around us. These conditions are important regarding seed storage and prolonging your seed mix life.

Generally, the conditions are:

Low Humidity Low humidity provides dry conditions for seeds, thus avoiding the potential initiation of germination.
Low TemperatureThe low temperature tends to decrease the respiration rate, slow down stored energy usage, and increase longevity.
Optimal temperatureThe optimal temperature for storing seeds and seed starting mix is below 42°F (15°C), while the relative humidity should be between 20 and 40%.

Temperature and humidity are inversely related here, meaning that as storage temperature reduces, the humidity will increase, and vice versa. However, storage times will increase if somehow both are godown.

Importance of moisture in seed mixes

Germinating seedlings on a plant nursery tray

The moisture level is a pretty important part if you want to enhance the life span of your starting seed mix.

So keep a look and try to make it as required because by creating optimal conditions for your seed starting mix, you will enhance their life span and use them over the next couple of years.

How to create your Seed Starting Mix

This is a basic recipe for creating a seed-starting mix for your plants. Also, you can further customize it as you grow the plants.

Startup by using lightly moist ingredients with a pretty fine water mist, then go ahead and blend thoroughly in a large container such as a wheelbarrow.

This is a simple tutorial that will help you create a pretty simple and effective seed starting mix. But as always, using a seed mix from the shop will be better and may have bigger improvements.

Ingredients for making a seed starting mix

Potting equipment on a wooden desk

You should consider buying a seed starting mix if you own a big land with many plants that make you revenue.

Four parts of screened compostA part of vermiculite
A part of perliteTwo parts of sphagnum peat moss

Doing this will be very helpful in saving money and being more connected to the seed-growing process.


Can I use an expired seed starting mix?

Seed-starting mixes prepared in the market will stay dormant for long periods. The product wrapping has no expiry date since it can be used for a few years. An expired seed mix can also work well because some seeds in the mix might have gone bad, but others may work for you. 

Which is the best seed starting mix in the market?

There are three fundamentals for the seed mix to work best. It must be sterilized and low in nutrients, and the texture must be light and porous. Any seed starting mix with the above three qualities is bound to work best for you, and you can purchase that without any worries.

Can I store my seeds at home in a refrigerator or a freezer? 

You can conveniently store your seeds or seed starting mix at home in your refrigerator or freezer. Specialized containers aren’t needed if you keep the temperature and relative humidity low. To see off the moisture problem, use silica gel packets placed in air-sealed plastic containers.

How do you Store Seeds or Seed Starting Mix in your Homes?

The normal home refrigerator is acceptable for storing. Storage temps near the 40°F mark work well. Store your seeds or seed mix in a plastic bag with the desiccant and carefully open them with proper warm-up so that condensation doesn’t occur on the surface of the packets or the seeds themselves.

Can you start seeds in egg cartons?

Yes, you can use egg cartons for starting seeds. You can use any container for starting seeds, whether old boxes, smaller containers, or such, as long as you ensure proper drainage. Make sure you can transplant said seed into a bigger container once it’s grown enough.

Conclusion with regards to seed starting mixes going bad.

So you have some clues on starter seed mix and how to get the longest shelf life for it. This information is the key for gardeners using the starter seed mix. However, taking care of the conditions of the starter seed mix is important. It’s comforting to know that the starting seed mix isn’t that sensitive, and we can use them without any worries.

If you’re a big business, we suggest you go ahead and stick with starting mixes from the stores. Now that we have the starting seed mix made and how you can use it, the gardeners can consider getting it for the upcoming years. 

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