9 Reasons Why Seeds Don’t Germinate

There Are At Least 9 Reasons Why Seeds Don’t Germinate. And It’s Often Not Really The Fault Of The Seed! This Article Explains Why Seeds Often Fail.

Seeds not germinating is disheartening for any gardener and the internet is full of complaints about poor seed. But there are lots of Reasons Why Seeds Don’t Germinate and it’s not always down to the seed.

Seed producers and packers in the UK have to comply with The Seed Marketing Regulations 2011 which covers a range of criteria including germination rates which are much higher than many gardeners expect. Failure to comply is a breach of the law and carries serious legal and repetitional consequences. So seed companies do all they can to ensure they are compliant.

Other countries have similar seed regulations.

Mistakes With Seed Happens

Sadly, mistakes do happen and I’ve been at the sharp end of at least one mistake.

It happened on my market garden. I bought a pack of Bellboy peppers, sowed them, produced 1500 plants and grew them on in some of my polytunnels. All went well until the fruit set. The crop was huge, the plants had done well. BUT they weren’t Bellboy peppers, they were chillis.

Of course it’s impossible to tell the difference when you look at the seed. So I couldn’t have spotted the mistake when sowing. And my complaint was upheld when other growers experienced the same problem. One batch of seeds had been mislabelled. Mistakes happen.

Actually it wasn’t a total disaster. I harvested the crop one the next few months and it brought in a good income. The gross margin was good.

We didn’t sue or anything like that. I had a good relationship with the seed company, ran trials for them and they took me out for a meal to apologise! It was all very amiable.

Worse would have been the seed not germinating at all. That means crop loss and, even as gardeners, that isn’t good news.

So What Prevents Seeds Germinating?

Compost Causes Poor Seed Germination

This is what most gardeners blame. Sometimes they are right, but often not as there are so many things that can inhibit germination. These gardeners frequently blame the poor quality compost and “prove it” by saying they sowed seed in two types of compost and one germinated and they other didn’t, even though they treated it just the same. That sounds like evidence that the compost is to blame .. BUT isn’t.

Most seeds will germinate in poor compost simply because they have enough nutrients in the seed to nourish them for several days. That’s provided they have adequate moisture, air and temperature. But when two composts are side by side though temperature might be the same moisture and air can be very different.

The clue is always when someone says they were treated exactly the same. If the composts are different they should be treated on merit. NOT as if they are the same. Different composts have different ability to absorb water and/or drain so cant all be treated the same.

Frequently when I examine offending composts the one where the seeds have failed has been overwatered to the extent that it has “slumped” and hence sat too wet. And if it is too wet then air is excluded and the seed will rot!

Treat each seed tray or pot own its merits, NOT all the same.

Noe let’s look at other seed germination issues …..

Old Seed Doesn’t Germinate

Just like gardeners seeds have a natural lifespan they cannot live beyond.

Some seeds only remain viable for a single season, others last 2-3 years and some last much longer. I once saw a field ploughed for the first time in at least 60-70 years and weighing weeks it was blood red with poppies. Poppy seed lasts for decades in the soil.

The oldest living seed known to mankind was a date palm seed taken from a site near Jerusalem. It was from an extinct species and over 2000 years old. Seven seeds germinated and have been grown on. there’s a video on the this extinct palm tree and its incredible seeds here.

Most veg seed dies after a few years. It depends on the species and how well it was stored, but it has a natural lifespan it cannot go beyond. There’s a seed lifespan list on this What Is a Seed? article.

Badly Stored Seeds Frequently Don’t Germinate

I often see garden centre seed displays in locations where the sun shines on the packet and they get very hot. This is in a store that at night often gets very cold! Both heat and cold can cause germination problems before the seed is even sown, and heat is the biggest problem in my view.

Germination Temperatures Are Too Hot Or Too Cold

Each species of plant has its preferred environment in which to live. And it has preferences for germination as well. Too hot or too cold will either kill them or make them dormant. Either way we don’t see the plants we want.

Seed such as tomatoes, cues, melons and even basil need a bit of warmth. True toms spring up everywhere once soil temperatures increase, but they are reluctant to germinate when it’s too cold.

Sweetcorn also need sufficient soil temperature to germinate. If the soil is too cold the sweetcorn just rots. That’s why some people start sweetcorn in pots. Though I think that is making hard work of it. Sowing seed later outside gives much better crops in my view and they can be just as early harvesting as pots, if you know what you are doing.

Other seeds prefer it a bit cooler. In many cases if it’s too warm they fail to geminate. Interesting some seed will still germinate if it is a bit cool for them, but will take much longer as the conditions are not ideal. In winter I germinate a lot of veg in modules in my unheated greenhouse. Veg you’d expect to germinate in 4-7 days in summer can take 3-4 weeks! But they still germinate eventually. And germination rates are often very good. Seeds such as lettuce, beetroot etc are in this category. Many people through the seed and compost out before they germinate at low temperatures and blame the seed.

Soil Moisture Problems That Affect Seed Germination

Seeds require moisture to germinate. Each species has its own requirement. If it is too dry or too wet they will fail.

Insufficient Light For Seeds To Germinate

Most seeds germinate under the soil in near dark conditions. But some of them need an instant of light to start the germination cycle. That’s not a problem when we sow seed as they get exposed to light as they come out of the packet!

But other seeds, such as celery, require light as they germinate. So they need surface e sowing and shouldn’t be covered with compost. To complicate this celery only needs light in the first year and then the need diminishes. We can thank Kinzel for research on this topic. In 1926 Kinzel researched the light needs of over 900 species of plant. And discovered some needed light and some didn’t. In fact light inhibits germination in some species.

Depth of Sowing Affects Seed Germination

Sow a small seed too deep and it might germinate but the seedling will be too small to reach the soil surface. Other seeds, when sown too shallow, will germinate but fail to get the root down and establish itself.

The general rule is to sow to a depth equivalent to the diameter of the seed. But many seeds haven’t read the rule book!

Seeds Eaten By Various Pests

Seed can be eaten by various pests after being sown. The pests can range from mice to barely visible insects. And some seed can be damaged by weevils, boring insects etc before being sown!

Damping Off During Germination

Damping Off is caused by fungi that infect the seed before, during or after germination. Which it is is irrelevant if the seed is killed!

There are chemicals that can be used to control damping off but the best cure is to ensure the compost isn’t over wet and that you maintain good hygiene.

Tag: Reasons Why Seeds Don’t Germinate

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