What needs to be fertilised now? And above all, how much fertiliser needs to be used?
For balcony and pot plants use a mineral soil such as a potting mix. The stored fertiliser can be easily raked through and is not washed out by frequent plant watering. The fertiliser reserve of a high-quality flower soil (normally added by the manufacturer) usually lasts for around six weeks. At this point, you need to add more fertiliser. I therefore add long-term fertiliser to the soil during planting - 2-3 grams per litre of soil. This is how I provide basic food for my plants up until August/September. I also add a small dose of liquid feed each week - 0.1 to 0.2 parts per thousand - when watering (i.e. 10 to 20ml of liquid feed for a full 10l watering can). Again: Follow the manufacturer's instructions on the fertiliser packaging!
In shrub gardens, the extent of fertilising measures mainly depends on the size of the mass formed by the leaves and flowers of the plants. I only fertilise rockery shrubs here and there with a handful of hornmeal or a little compost (barely a litre per square metre). Strongly growing bed shrubs can be given around 50 grams of compound fertiliser per square metre in spring (around March/April). Alternatively, you can give them around three litres of compost per square metre. Weaker growing shrubs only need 30 grams or 1.5 litres. In mid-June you can feed them again with a second, slightly reduced amount.
In vegetable gardens, the extent of fertilising measures mainly depends on the type of plant, since because vegetable plants can be divided into strong consumers, including cabbage, medium consumers such as tomatoes and weak consumers such as lettuce. Here are some individual fertilising recommendations:
Weak consumers: Add 1 to 2 litres of compost per square metre and, if necessary, additional nitrogen (approx. 70 grams of hornmeal per square metre) and potassium (approx. 35 grams of potassium magnesium fertiliser per square metre).
Medium consumers: Add 2 to 4 litres of compost per square metre and, if necessary, additional nitrogen (approx. 120 grams of hornmeal per square metre) and potassium (approx. 70 grams of potassium magnesium fertiliser per square metre).
Strong consumers: Add 4 to 6 litres of compost per square metre and, if necessary, additional nitrogen (approx. 150 grams of hornmeal per square metre) and potassium (approx. 100 grams of potassium magnesium fertiliser per square metre).
Important: Cabbages, onions and carrots should not be placed on surfaces freshly fertilised with manure. Only add these plants to such areas the following year. There is a risk of intolerance here, since some manure attracts flies whose larvae can mine into the plant.
When fertilising grass areas please note the following (as already stated in the Lawn Special): When you cut the grass, you also remove nutrients from the lawn. For each kilo of trimmings you remove around 30 grams of nitrogen, 20 grams of potassium and 10 grams of phosphorous. You have to replace these nutrients. Decorative lawns need somewhat less fertiliser than lawns which are walked on or are under stress. You normally fertilise lawns every four to five weeks from September/October, ending with a final autumn fertilisation to prepare for the winter at the start/middle of March. However, differences do exist now that long-term lawn fertilisers and special autumn fertilisers have come to the market. As we keep reiterating, you must pay close attention to the manufacturer's information on lawn fertiliser packets. This can also help to answer the question of whether you can use composite fertiliser rather than lawn fertiliser. Take a look at the mix ratio of composite fertiliser - nitrogen: phosphorous: potassium. For lawns, this is ideally 10:3:3-5.
To fertilise trees, you first have to differentiate between deciduous trees and evergreens. Their annual growth cycles are rather different, which is why they need fertilisers at slightly different times.
Deciduous trees mainly need their nutrients at the start to middle of December and then around mid-January to mid-February for a second growth spurt. After that, you should not fertilise them further. Thus, you actually apply fertiliser to deciduous trees for the first time in April (around 55% of their annual requirement) and in December (45%). The figures vary slightly for fruit trees and roses, which require a 50/50 or 60/40 split.
Evergreens need their first nutrients in November and a second, higher dose between the end of January and the end of February, when they are forming cones. The feed distribution for evergreens is therefore 35/65.
The fertiliser quantity also depends on the plant's requirements, i.e. the mass each plant forms. For small conifers, around 35 grams of composite fertiliser per square metre and per year is sufficient; for the maintenance fertilisation of trees and bushes around 50-70 grams of composite fertiliser per square metre and per year should do the trick, and for fruit trees, roses and rhododendrons you can go to the upper limit and add 100 grams in both doses.
Please note that the tree roots must be able to access the nutrients at the stated times. If you want to use organic fertiliser, you have to add the waiting period for decomposition to the times stated above.