Pre-growing plants: The right soil

If you want to sow and grow your own plants, the right soil is very important for strong and healthy growing plants. Because the young seedlings have somewhat different needs and demands on the soil than the adult plants, we want to look in this article, how the ideal growing soil should be and why this is so important.

Soil: A little soil crash course

The soil we normally find in our garden is usually made up of humus, clay, sand and silt. These components can vary in concentration and significantly affect the properties of the soil. Loam, for example, is an excellent water retainer, but in high proportions can cause the soil to become very nutrient rich, but also too dense and impermeable. Sandy soils, on the other hand, tend to be loose and generally do not store quite as many nutrients and also less water than very loamy ones, but waterlogging is less likely to occur and plenty of air gets to the roots. Humus provides the soil with nutrients and usually raises the pH value slightly.

No matter what type of soil it is in the end: They all contain more or less nutrients and salts. In addition, millions upon millions of tiny microorganisms cavort in the soil. Worms, amoebae, fungi – these are just a few of the many soil inhabitants that ensure that the valuable, nutrient-rich humus is created from dead leaves and other natural waste and that the soil is well aerated.

Potting soil or growing soil?

If you want to grow your own plants from seed, you should choose the right soil to make the season a success for you. We distinguish between ordinary potting soil (which includes the normal soil in your garden bed) and growing soil. Growing soil is also often referred to in the trade as “potting soil”, “herb soil” or “sowing soil” – apart from the names, however, they do not differ from each other any further. If we now sow and grow plants ourselves, we must therefore resort to the growing medium. You can also easily mix your own ideal potting soil, but we’ll get to that below.

Potting soil: properties

Growing soil differs from potting soil in several ways. On the one hand, it is low in nutrients and salt. It is also very permeable, but at the same time retains water relatively well. In addition, good growing soil is virtually germ-free and contains as few fungal spores, pathogens, pests and weed seeds as possible. Normal garden soil or commercial potting soil, on the other hand, is not sterile. In general, you should always use growing soil for this purpose when it comes to propagating and rooting your plants (i.e., even when rooting cuttings or woody cuttings). We have already written a small guide to cutting cuttings using houseplants as an example – a good idea if you have had little or no experience with this and would like to practice first.

The ideal growing soil

Less is more: nutrients only in moderation

The perfect soil for growing is loose, permeable, rich in humus, low in nutrients and as germ-free as possible.

Why is this so important for seedlings? For one thing, nutrient-poor growing soil stimulates root growth; you can think of the roots as little antennae that the plant pushes through the soil in search of lots of nutrients. They literally have to work harder than if all the nutrients were already present in abundance, which results in faster and stronger growing, robust roots. And of course we think that’s great!

On the other hand – and this is even more important – the sensitive, newly formed roots cannot cope with the many nutrients and salts of normal soil and can even be damaged, they are literally burned by the salts. This would result in stunted or completely dead seedlings and plantlets. And that, in turn, is something we want to avoid at all costs, of course.

Germs are not welcome

Unfortunately, the numerous microorganisms in soil and planting soil also include the odd fungus gnat larva, mold spores and various pathogens. This is perfectly normal, and seasoned, hardy plants can handle most of them without suffering major damage or dying immediately. Seeds and tender seedlings, on the other hand, have absolutely no resistance to the pests and would be immediately destroyed in the event of an infestation. Since the seeds are usually covered under a canopy and a warm, humid greenhouse-like climate is created, pathogens have an easy time of it. Especially for molds, such conditions are like a wonderful wellness oasis, where they can spread wonderfully and infest everything.

For this reason, growing soil is sterilized in advance by heat. If you want to mix your own soil, you should not do without this step. This also destroys the seeds of weeds that may have crept in and could displace the seedlings.

Pre-growing plants: The right soil
The tender seedlings cannot yet successfully defend themselves against pathogens

Where can I get growing soil?

You can get potting soil in different ways. Of course, going to the hardware store or a nursery is one option. In any case, you should choose soil that is peat-free. This is not only better for the environment; peat also has the unfortunate property of compacting and hardening when dry. Our tender seedlings can’t use either. Nevertheless, there are always growing media that contain peat – so don’t forget to look at the list of ingredients.

Mix it yourself

Then, of course, there is the option of simply mixing your own growing soil. Let’s first take a rough look at what components make up good growing soil. An advantage of the whole thing is that you can find most of the ingredients for it at home and thus also save costs.

Growing soil is composed of three components: You need equal parts each of loose garden or potting soil, sand and mature compost. Perlite (a foamed volcanic mineral that looks like white Styrofoam balls) can also be added, they significantly improve the looseness and aeration of the soil and additionally help to avoid waterlogging. However, they are not a must!

For the soil component, pretty much any soil will do; it can be either simple garden soil from your beds, old planting soil or, even better, the soil from molehills. It is particularly fine crumbly – a good reason to tolerate the little digging masters in the garden.

Pre-growing plants: The right soil
Maybe you are creating a new bed anyway – then you can use the garden soil to mix growing medium.

For compost, pretty much any compost will work. But if you have the chance to get leaf compost or compost from lawn clippings, choose this one. It is particularly high quality and fine. In any case, the finished growing mixture must be sterilized or disinfected in the oven at 120 to 150 degrees for about 30 – 45 minutes at the end, and after cooling it is best to use it quickly.

Make sure, however, that there are no larger insects such as woodlice or even earthworms in the soil. To spare them, you can roughly sift the soil beforehand.

This is only a very rough “basic recipe”; depending on the variety and nutrient requirements of the respective plant, the mixture can of course be optimized and adapted. And because the topic is quite extensive in itself, you will find more about it in our soon to be published guide.

Pre-growing plants: The right soil
This soil should first be coarsely sieved to sort out unrotted matter and small insects

From the nursery into the open

However, we still have to clarify one question: At what point can the young plants move into normal planting or garden soil?

Here there is not really a completely safe patent remedy. Some sources say that the plants should be transplanted into normal soil from a size of about 10 to 15 cm, which in itself is a good guideline. Others say that the plants should be transferred to potting soil as soon as they are pricked out, because they need more nutrients as they grow. The problem is that potting soil is not always the same as potting soil. Some soils – but not all – are very heavily fertilized, which would be too much for the still tender seedlings. A good option is to mix the growing soil with potting soil or even more compost. This way you get a kind of “transitional soil” that provides the seedlings with important nutrients. Rely on your gut feeling and don’t be afraid to experiment a little, especially in the beginning. In general, once the young plants are visibly strong and have grown nicely, you can plant them out as soon as the temperatures are right.