Slow Germination? Possible Causes and Solutions

Almost every grower has experienced it – you sow the seeds and wait in anticipation for the first leaves. After a few days, however, it seems the seeds are showing no signs of life. Where did it go wrong? There could be several reasons, so let's take a closer look. In today's article, we will focus on the causes of slow germination and how to prevent it.

Before we dive into answering what might be causing slow germination, let's answer the question: how fast should seeds actually germinate? Germination speed depends on several factors – such as temperature, humidity, light intensity, but also the species. While some seeds can germinate as early as the second day after sowing, others may take several weeks. Therefore, be patient and find out what germination period is typical for the given species.

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Low or Fluctuating Temperature

Temperature has a huge impact on germination, and most seeds germinate best at temperatures between 22-26 °C. In nature, rising temperatures are a signal for seeds to wake up. If it is too cold, the germination process can take significantly longer or stop completely. Fluctuating temperatures are also a problem, which is common especially when germinating on a windowsill.

How to do it:

• Place the sowing in a warm place with a stable temperature – for example, on a radiator-heated windowsill or, even better, in a heated propagator.
• Use a heat mat to keep the seeds warm and ensure a stable temperature.
• If you are sowing seeds outdoors directly into the soil, check the temperature first with a soil thermometer.

Incorrect Humidity

Everyone knows that seeds need water and will not germinate in a dry substrate. However, many growers make the mistake of germinating in waterlogged substrate, which increases the risk of rot, mold, and damping off. Seeds need an evenly moistened and simultaneously airy substrate.

How to do it:

• Use propagators during germination – miniature greenhouses that maintain a stable microclimate.
• Use a seedling substrate or starter cubes (plugs) made of rockwool, peat, coco, or Easy Plugs for germination.
• If the substrate dries out too quickly, moisten it with a pressure sprayer to avoid washing away the seeds.

Seed Quality and Age

Sometimes you are not to blame for slow germination, but the seeds are. Old seeds have lower germination rates, especially if they were not stored correctly, for example, in light, heat, or humidity. In such a case, your chances of success are low, but not entirely non-existent.

How to do it:

• If you have any seeds left, perform a germination test. Take a few seeds and let them germinate on cotton wool or a paper towel.
• Try to support the seeds with a germination booster.
• Buy seeds from reputable and reliable sellers. At Higarden.cz, you can find seeds for chili, herbs, or microgreens with a clear origin.

Incorrect Sowing Depth and Heavy Substrate

It often happens that ungerminated seeds remain trapped in a layer of substrate that is too deep and cannot break through to the surface. The sprout either breaks or exhausts its energy before it reaches the light. The reason may be an unsuitable substrate or sowing too deep.

How to do it:

• Generally, the sowing depth corresponds to 2 to 3 times the length of the seed.
• Choose a light soil substrate for sowing or use starter plugs and cubes.

Unsuitable Light Conditions

Germination for most plants takes place in the dark, but as soon as the first leaves appear above the surface, they immediately need light. It is often best to germinate under a grow light. The lighting should reach an intensity of 50 to 150 µmol/m²/s with a photoperiod of 16-18 hours per day. A lack of light will cause the sprouts to grow slower, turn pale, and start stretching (bolting).

How to do it:

• Use a growth light when germinating and growing seedlings. TLED panels with a growth spectrum are excellent for these purposes.
• Hang a grow light with a power of up to 120 W about 10-40 centimeters above the tops of the plants.

Molds and Damping Off

A humid and warm environment is ideal not only for germination but unfortunately also for molds and pathogens, for which sprouts are easy prey. The result of an infestation can be both slow germination and stem rot, which kills the plants.

How to do it:

• Use sterile substrate and clean growing containers, which you should wash with boiling water or a disinfectant solution for growers before use.
• Treat the seeds and substrate with a product containing Trichoderma – a beneficial fungus that protects the roots.

Slow germination is no reason to panic. Often, a few small adjustments are enough for success to arrive. When germinating, monitor the temperature, humidity, and light, and use a high-quality substrate. Proper care for your seeds will surely pay off. And if you are unsure about anything, check out the Higarden grow blog, where you will find many useful tips and advice for beginners, or contact our experienced sales staff.