How Long Does Grass Seed Last?

Are you dreaming of a lusciously green lawn?

Scattering your lawn with grass seed at the right time is a great way to fill in patches and boost its overall appearance.

If you’ve bought grass seed out of season, there’s no need to panic – storing it properly will help it last until the following year. However, if you’ve found a box of grass seed from ten years ago in your garden shed, you may be wondering if it’s still okay to use.

Here’s everything you need to know about how long grass seed lasts, including whether it expires, how you can tell if it’s still good, and advice on how to store it properly. 

Does Grass Seed Expire?

Let’s start with the most pressing question of whether grass seed expires.

Like many things, the answer isn’t quite as clear cut as you might hope. Grass seed is pretty resilient and can last for a long time – it won’t necessarily expire, but its germination rate will reduce the longer you have it for.

When you first buy grass seed, you can expect an 80-90% germination rate of the seed. This means that at least 80% of your grass seed is likely to sprout once sowed. Every year, the germinate rate will gradually decrease. That’s why it’s better to sow your grass seed almost immediately after purchase. 

If you’re looking to buy some grass seed, you might like to check out our Ultimate Guide to the Best Grass Seed Products.

How Can I Check If My Grass Seed is Still Good?

The best way to know if your grass is still good to use is to conduct a DIY germination test (very scientific, I know).

Here’s what you need to do:

1. Take a handful of seeds
2. Place the seeds in kitchen roll and spray it with water
3. Wrap seeds up and place in a clear container
4. Leave on a sunny windowsill
5. Spray the seeds with water when the paper towel gets dry

If, after two weeks, your seed hasn’t sprouted, it’s likely no good.

How Long Does Grass Seed Last in Storage?

Grass seed stored properly can last up to five years. However, with every year that passes, the viability of your grass seed will reduce by around 10%. 

For the best results, use your grass seed immediately or within the first three years of purchase.

To prolong its life, it helps to keep grass seed in an air tight container – this could be a plastic box, or a sealable bag. 

How Do I Store Grass Seed Properly?

To help your grass seed last longer, storing it properly is important. For the best results, store your seed:

• At room temperature – Anywhere around 15°C is ideal to avoid grass drying out.
• Away from direct sunlight – Seeds left in the sunlight can quickly lose their viability, so it’s best to store them in a cupboard, shed or basement.
• Somewhere dry – Grass seed left in humid conditions will absorb the moisture from the air, making it less likely to germinate. Using a dehumidifier could help maintain a more appropriate environment.
• In airtight packaging – Stopping excess moisture from reaching the seeds will keep them from getting damp.

Why Didn’t My Grass Seed Grow?

There are several reasons why your grass seed may not have sprouted the way you wanted it to. The most common reasons are:

• Planted at the wrong time – Spring or Autumn is best.
• There was a lot of footfall after it was planted – Grass seed needs to be protected, and not walked on, for up to 8 weeks after planting. Check out our article on lawn seed aftercare for more details.
• Too hot/dry – Seeds without enough water can quickly die out.
• Too wet – There’s a fine line between enough water and too much when it comes to grass seed (and grass in general!). Grass seed may not have survived if it was watered too much or the weather just wasn’t on your side. Although you can’t control the rain, using a sprinkler system can help avoid overwatering by hand.
• Too shady – Grass needs a lot of sunlight to survive. If the patch you tried to grow was too shady, it may not have stood a chance.
• It wasn’t good to begin with – If the seed was too old or hadn’t been stored properly, it may unfortunately have been doomed for failure from the get-go.

How Long Does Grass Seed Last Without Water Once it’s Been Sowed?

Without water, grass seed that’s just been sowed can last a few weeks, so there’s no need to panic if you’ve forgotten to water it.

However, grass seed that’s already sprouted will only last a few days without water. If the rain isn’t helping you out, it’s best to get out there with the hose, or sprinkler, as soon as you can.

How to Get the Best Results from Grass Seed

Here’s a quick recap. For the best results from your grass seed, make sure you:

• Store it well
• Use it within the first year of purchase
• Sow at the right time
• Look after it properly once sowed

If you do all these things, you should have a luscious lawn in no time! I also recommend you take a look at our article with additional tips on how to make your grass greener.

Has your Grass Seed Already Expired?

We’ve all been there! 

If your grass seed didn’t pass the germination test, it may be best to chuck it out on the patio for the birds to enjoy. At least it won’t have completely gone to waste!