How to germinate seeds

The germination of vegetable seeds is the process of growing plants directly from seeds rather than growing them from cuttings or buying plants that have already been grown. Although this may seem like a simple process, following some good practices is essential for success. This is why we’ve prepared this step-by-step guide to help you achieve this.

Sowing seeds indoors is a common technique among those who have orchards or gardens in their backyard, or who simply want to plant in a pot on their balcony. This is also a popular method for those who live in more northern areas, where young seedlings may have difficulty surviving in cold conditions. Germinating seeds indoors is an effective way of increasing the germination rate as compared to when this is done outdoors, directly in the soil.

If properly preserved, seeds can remain in perfect condition for months or even years. This is because their shell keeps them protected and in a dormant state until the right conditions arise for germination to start.

To store the seeds properly, humidity levels should be kept between 10 and 20%. Lower levels than this could lead to them becoming totally dehydrated, whereas higher levels could trigger the germination process sooner than desired. It is also vital that they aren’t exposed to either excessively high temperatures or sudden thermal changes. To prevent this, many growers choose to store them in the fridge.

Under the right conditions, the seeds start to hydrate and activate their metabolism until they swell and open. Once this happens, the radicle appears, which is the part of the plant’s embryo that develops to become the main root. Afterwards, the plumule is pushed up towards the surface to become the stem and leaves.

Factors to take into consideration for germination

Regardless of the method used, it is important to follow some basic guidelines to successfully germinate the seeds. Remember that this is the first stage of life of your plants, which is when they are most delicate and vulnerable:

• Keep a warm ambient temperature (between 18 and 26ºC).
• Try to keep the relativity humidity level between 75 and 90%.
• Once the seeds have germinated, avoid excessive watering.
• Wear latex gloves to manipulate the seeds, but try to do so as little as possible. Avoid touching the radicles at all costs.

There are certain devices called seed germinators or greenhouses, of various sizes and characteristics, which are specifically designed for optimal seed germination. Having a water sprayer available is also useful, if not indispensable.

Which germination techniques are there?

There are several ways to germinate seeds, and each grower chooses the one that best suits their preferences. Here we explain how to follow some of the most popular ones:

Seed germination in water

Although this method is quite popular, it is not the most effective:

• Place the seeds in a glass or container with warm water (at a temperature of around 23ºC). Keep in a dark place.
• From the third day, the seeds should start to open, thereby freeing the radicles.
• When the roots are 3 mm long, it’s time to move them to the growing medium (previously moistened). Make some holes (1-1.5 cm deep) and gently put the germinated seeds into them, trying to place the radicle facing downwards. Then cover them without exerting pressure.

Paper napkins: an old school method that still prevails today

This is probably the most frequently used method, as it ensures a good germination rate. For this, you need some paper napkins or kitchen paper, which are great for maintaining high humidity levels.

• Moisten some pieces of paper and place them on the flat base of a container that has a lid so it can be covered up.
• Place the seeds on the paper, keeping some distance between them. Cover them with more damp paper.
• Close the container to maintain the humidity level, but allow for some airflow (you can make some holes) to prevent the appearance of mould or fungi.
• Keep the container in a dark place.
• From the second day, the seeds should start to open, thereby freeing the radicles.
• Move the germinated seeds to the substrate following the process explained in the previous method.

The greatest advantage of this technique is its high success rate, although it is crucial to keep the napkins damp at all times, preventing them from either drying up or becoming too soaked.

How to germinate seeds in Jiffy or rockwool

Jiffy pellets made of peat and/or coco coir, as well as certain rockwool compounds, can greatly facilitate the seed germination process as they help maintain good humidity levels and have a compact structure that is ideal for the initial development of the roots. Germinating seeds in these materials is really simple:

• Dampen the Jiffy pellets or the rockwool, keeping the pH between 5.6 and 6.2.
• Make some holes at a depth of 1 to 1.5 cm.
• Place the seeds in the holes.
• Once the seeds have germinated, the seedlings can develop their roots in this growing medium and don’t need to be transplanted to substrate until the cotyledons (i.e. the first pair of leaves) have appeared.

Germinating the seeds directly in the substrate

If done correctly in a suitable, healthy substrate, this technique is highly effective. Growers who choose this option normally do it in small pots, by previously dampening the growing medium (either soil or coco coir) and by placing the seeds in small, 1-1.5 cm deep holes before covering them. You can also soak the seeds in warm water for 12 to 24 hours before planting them.

• It is important not to press the substrate too much to facilitate the development and oxygenation of the first roots. If done correctly, the seedlings will appear on the surface from the third or fourth day.

The main benefit of this method is that you don’t need to move or manipulate the seeds, which in turn reduces the risk of any stress factors (as long as the seeds are not buried too deeply). Besides, germinating directly in the substrate helps keep temperature and humidity stable.

Regardless of the technique that you use for the first few phases of germination, it is vital to keep the lighting, temperature, and humidity parameters under control once the seed is in the pot with the substrate. As has already been mentioned, your plants are like ‘little babies’ at this stage, and excessive irrigation, for instance, could lead to the appearance of fungi and the subsequent withering of the first roots.

Now that you’ve learned about the different germination techniques and which mistakes you must avoid with each of them, you’re ready to start your own experience. We wish you a great start!