Fertilizing is a subject that can be covered either in one sentence or in a book. The short version: buy a liquid green plant fertilizer and follow the instructions on the package. We offer you a wide selection of good fertilizers in our store and web store without any complications. And the long version:
NPK and trace elements
Fertilizer consists of three main components: Nitrogen (N), phosphate (P) and potassium (K). These components are core nutrient elements and, because of their importance, are part of every fertilizer. Plants only absorb the nutrients they need. At the same time, too high a concentration of a nutrient in the soil (accumulated because the plant needs it only in small amounts, but it was fertilized anyway) is bad (see the topic of watering). Therefore, too much fertilizing is harmful to the plant.
In the garden center you are overwhelmed by fertilizers for all kinds of plants and mixing ratios of N, P and K. Here's a secret: very much of it is pure marketing. If you flush the soil regularly, as described in the watering topic, the mixing ratio almost doesn't matter. Because that way, no nutrient can accumulate in the soil. So we say: grab any green plant fertilizer and use it as it says on the package, and flush the soil every few months.
Those who have more sensitive plants such as orchids, terrarium plants, rare and fragile philodendrons or anthuriums should also think about the trace elements. In many commercially available fertilizers some trace elements are missing, in the worst case they can be missing completely. They are especially important if you water with rainwater, distilled water or osmosis water. These are, in fact, completely free of any trace elements. Many fertilizers, for example, do not contain calcium or magnesium because they are present in tap water (even if in poorly absorbable form). Good fertilizers contain nutrients that can be easily absorbed by the plant.
Organic or mineral
Organic fertilizers such as horn shavings, manure or bone meal are not recommended for houseplants. For one thing, they do not contain all the core nutrient elements, and for another, it is difficult to estimate how they will work. They lack microorganisms to release the nutrients, which can take months to years, even in the garden. Plus, they can be quite stinky... 🙂
So better use mineral fertilizer. The main advantage of organic fertilizer is that it is difficult to burn due to overfertilization. But if you regularly flush the soil, this should not happen even with mineral fertilizer.
Fertilize in winter
In winter, plants grow less and also need less fertilizer. If you have grow lights, however, you should continue to fertilize. You can also fertilize as easily during the winter, as long as you keep flushing the soil, it shouldn't be a problem.
How much should I fertilize?
In general, you should follow the instructions on the package. If you regularly flush the soil, underfertilizing is a greater "danger" than overfertilizing. Even if the plants need different amounts of fertilizer, as long as you flush away the accumulated fertilizer, there is no risk of overfertilization.
However, there are plants that should really be fertilized only weakly, these would be orchids and sensitive terrarium species. Carnivorous plants should not be fertilized at all and should only be watered with rainwater.
Slow release fertilizer
Often these fertilizers come in the form of beads (like Osmocote or Lechuza, which is also Osmocote ultimately) or sticks. They slowly release their nutrients into the soil. In our experience, this works pretty well. However, to make sure that not too many nutrients get dissolved, you should still flush through every now and then. Also, such fertilizers often do not contain all trace elements, so you should use a good liquid fertilizer now and then.