Water quality, minerals, fertilizers
At least in Berlin tap water comes with lots of calcium (Chalk), sodium (Natrium) and magnesium salts that will build up in the soil and roots. Somewhere else tap water can also contain chlorine and fluoride which are harmful to plants, especially to spider plants, Dracaena palms and calatheas.
Take only cold water from the tap and let it sit in the can at least one day before given to plants. This will help as most of the salts will settle to bottom and possible chlorines and fluorides will evaporate. Don't use the bottom part of the water.
Use rain water, melted snow or spring water when possible. If you use distilled water, keep in mind that plants need minerals too. Distilled water has nothing left and you need to add some minerals back to the water.
The same goes when you are misting your plants, white water spots are not so nice on the plant leaves. This can also lead to permanent leaf spotting.
Not all fertilizers are the same and every plant's need is different. N-P-K numbers on fertilizer will tell you how much nitrogen (N), phosphorus (P) and potassium (K) is included by weight.
With balanced universal fertilizers you see numbers like 10-10-10 or 20-20-20 etc. Higher the numbers, more stronger fertilizer you have.
Over-fertilizing can burn your plants roots.
First of all, you need to check suggested dosage from the fertilizer bottle. We suggest that you dilute everything by half of the recommended limits at the bottle. Another way to avoid over-fertilizing is to choose a product with low percentages of each macronutrient (10-10-10 and below).
Make sure that the plant is well-watered before giving diluted liquid fertilizer, this will help to avoid root burning.
Avoid fertilizing your plants in fall and winter when they are partially dormant. Excess fertilizer adds to salt buildup.
We don't go deep what minerals are essentials and which/why each other is required as this is not our specialities. At our shop we don't use fertilizers at all as plants stay there usually very short periods. At home we have lots of different type of plants and to keep it simple we use universal low strength fertilizers for all green plants.
We have collected some basics here, but these are only estimated suggestions as we don't know what kind of soil your plant sits and what is lacking in the soil. Anyway this is something what you can start with:
|Plant family||Fertilizer N-P-K||How often and when|
|Calathea, Maranta, Stromanthe, Anthurium, Spathihyllum, Strelitzia, Ficus, Aglaonema, Philodendron, Oxalis, Monstera, Epipremnum, Scindapsus, Pachira, Dieffenbachia, Syngonium, Cissus, Begonia||10-10-10||monthly, from spring to fall|
|Peperomia||10-10-10||3 times per year|
|Zamioculcas||10-10-10||1-3 times per year|
|Alocasia||10-10-10||every 2 weeks, from spring to fall|
|Tillandsia, Bromeliad||17-8-22||4 times per year|
or ready made Tillandsia spray
You should not fertilize cacti or other succulents, like sansevierias. But if you do so, use then only a liquid cactus fertilizer at quarter strength of what is says on the label.