Slow germination? Possible reasons and what to do about it

Almost every grower has experienced this: you sow seeds and wait eagerly for the first leaves. After a few days, however, it seems that the seeds are not coming to life. Where did the mistake happen? There may be several reasons, so let us take a closer look at them. In today’s article, we will focus on the causes of slow germination and how to prevent it.

Before we answer the question of what may be behind slow germination, let us first ask how quickly seeds should actually germinate. Germination speed depends on several factors – for example temperature, humidity, the amount of light, and also the species. While some seeds may germinate as early as the second day after sowing, others may take several weeks. Therefore, be patient and find out what germination time is typical for the given species.

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Low or fluctuating temperature

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

How to do it:

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

Incorrect humidity

Everyone knows that seeds need water and will not germinate in dry substrate. However, many growers make the mistake of germinating in waterlogged substrate, which increases the risk of rot, mould and damping off. Seeds need a uniformly moist yet airy substrate.

How to do it:

• When germinating, use propagators – miniature greenhouses that maintain a stable microclimate.
• Use a seed-starting substrate or sowing cubes (rolls) made of rockwool, peat, coco or Easy Plugs.
• If the substrate dries out too quickly, moisten it with a pressure sprayer so that you do not wash the seeds away.

Seed quality and age

Sometimes slow germination is not your fault, but the fault of the seed stock. Old seeds have lower germination rates, especially if they have not been stored properly, for example in light, heat or damp conditions. In such a case, your chances of success are low, but not completely lost.

How to do it:

• If you still have some seed stock left, carry out a germination test. Take several seeds and let them germinate on cotton wool or a paper towel.
• Try supporting the seeds with a germination growth stimulator.
• Buy seeds from reputable and reliable sellers. At Higarden.cz, you will find chilli, herb and microgreens seeds 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 push through to the surface. The sprout either breaks or runs out of energy before it reaches the light. The reason may be unsuitable substrate or sowing too deep.

How to do it:

• As a general rule, sowing depth should be 2 to 3 times the length of the seed.
• For sowing, choose a light soil substrate or use sowing rolls and cubes.

Unsuitable light conditions

Most plants germinate in the dark, but as soon as the first leaves appear above the surface, they need light immediately. It is often best to germinate under 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 seedlings to grow more slowly, become pale and start to stretch.

How to do it:

• When germinating and growing seedlings, use grow light. TLED panels with a growth spectrum are excellent for this purpose.
• Hang grow light with an output of up to 120 W 10-40 centimetres above the tops of the plants.

Mould and damping off

A moist and warm environment is ideal not only for germination, but unfortunately also for mould and pathogens, for which seedlings are easy prey. The consequence of infection may be both slow germination and stem rot, which will kill the plants.

How to do it:

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

Slow germination is not a reason to panic. Often, a few small adjustments are enough and success will follow. When germinating, monitor temperature, humidity and light, and use a quality substrate. Proper care for seeds will certainly pay off. And if you are unsure about anything, take a look at the Higarden growing blog, where you will find many useful tips and advice for beginners, or contact our experienced sales staff.