Most plants in your garden need fertilizer, but it comes down to fertilizing correctly. Mistakes can cause serious damage to plants or even be fatal. Learn which mistakes are the most common and how best to avoid them.
Too much fertilizer: danger of deadly overfertilization
When fertilizing, the principle of “a lot helps a lot” does not apply at all. If you are too generous with the fertilizer, the plants will not grow more vigorously, but may even die. This can lead to deadly overfertilization. There can sometimes be interactions between different nutrients in the soil, but also between nutrients and plants. Fertilizer often contains phosphorus. If plants receive too high a dose of it, they can no longer absorb iron and manganese to the extent they need. Although the nutrients are present in sufficient quantities, your plants will suffer from deficiency symptoms. If you give too much nitrogen fertilizer, this will have a positive effect on the leaves, but the plants will produce few flowers, which will have a corresponding effect on the harvest.
You can recognize overfertilization by various signs:
- Burning of the leaf edges
- wilted leaves
- susceptibility to diseases
- lack of resistance to wind and weather
With too much fertilizer, you are not only harming the plants, but also the environment. If rain washes out the excess nutrients, they can leach into groundwater. It also has a negative effect on people’s health if fruit or vegetables are fertilized too much. If too much nitrogen is applied, harmful nitrate can accumulate in the plants. In the human body, this can be converted into the carcinogen nitrosamine.
Overfertilization: How you can still save your plants
If you have fertilized your plants too much, it doesn’t have to be too late. Give your plants a break first and don’t fertilize. By watering heavily, you will reduce the concentration of fertilizer in the soil. However, be careful not to allow waterlogging to form, as it can cause plants to rot. If your plants manage with little water and too intensive watering harms them, the only thing that will help is to change the soil. Remove the over-fertilized soil around the plants and add new soil to the planting holes.
Avoid overfertilization: pay attention to correct dosage
There is no magic formula for how much fertilizer your plants need and how often you should fertilize. Fertilizer needs depend on the plant species, soil and location. If you use fertilizer from the garden store, pay close attention to the dosage instructions. This also applies to the frequency of fertilizing. If you are not sure, use too little fertilizer rather than too much, and fertilize less often rather than too often.
The wrong fertilizer: pay attention to the type of plant
Look at the offers of fertilizers in the garden market, you will find the right fertilizer for many types of plants such as tomatoes, berries, conifers or flowering plants. However, there is also universal fertilizer, which is suitable for many types of plants. In most cases, this universal fertilizer is cheaper than special fertilizers. However, since plants have different requirements for fertilizer, it is not always wise to buy universal fertilizer.
Pay close attention to which soil and which nutrients the individual plant species prefer. Rhododendrons and hydrangeas like acidic soil and may be sensitive to fertilizer mixtures containing lime. Tomatoes are quite demanding when it comes to nutrients. They are grateful for a special tomato fertilizer, because it has a lower concentration of nitrogen, which could negatively affect the harvest.
Tip: Some vegetables, such as cabbage plants or potatoes, are heavy growers. They need nutrient-rich soil and can hardly get enough fertilizer. However, you should use chemical fertilizers sparingly. Better suited are manure or nettle liquid manure.
pay attention to the soil: pH analysis can help
A common mistake when fertilizing is to simply fertilize without knowing what nutrients the soil even contains and what its pH is. Fertilizers can be used to change the pH value. Therefore, it is important to know the pH requirements of individual plants and to perform a pH analysis of the soil. Garden plants usually prefer a pH of 5.5 to 6.5, and you can get test strips or special testers to measure pH at hardware stores.
You can use lime to balance a pH that is too acidic and lower than 5.5. Alkaline soil that has a pH higher than 6.5 can be made more acidic with an acidic substrate.
Not only pH, but also soil type such as sandy soil, clay soil or humus is important in deciding how much of which fertilizer is needed. Soil nutrient concentrations can also vary within a soil type.
Tip: Have a soil analysis done in the lab about every three years, taking samples from several locations in your garden. This will tell you what nutrients your soil still needs. You’ll also get tips for using the right fertilizer.
Pay attention to the weather: Do not fertilize in the sun
If the sun is shining intensely, gardening is fun, but it is not a good time to fertilize. Liquid fertilizer can cause serious burns to plants when exposed to sunlight. Since fertilizer is more difficult to spread on dry soil, it has an uneven effect.
- in the morning, when the soil is still damp from dew,
- when the sky is overcast, because then the soil does not dry out so much, or
- after a downpour, as the fertilizer is then better absorbed.
In winter, your plants do not need fertilization, as they then usually take a rest. Only in spring do you slowly start giving fertilizer again. Most plants only need to be fertilized during the growth phase.
Too much chemistry: severe plant damage possible
There are a variety of chemical fertilizers for the different types of plants. However, this can affect the nutrient uptake of the plants and cause damage to them. Better suited is organic fertilizer, as it is less damaging to the plants and better tolerated. Organic fertilizer such as horse manure or compost releases nutrients more slowly to plants and soil, making it an optimal slow-release fertilizer. The advantage is that you do not have to re-fertilize as frequently. The nutrients are less likely to be washed out by rain and do not pollute the environment. Good for numerous plant species is plant slurry as fertilizer, for example, from nettles or horsetail.
Tip: In addition to plant slurry, compost or horse manure, you can also use home remedies such as chopped banana peel, coffee grounds or water from boiling eggs as fertilizer. These home remedies don’t have to end up in the trash, as they provide valuable nutrients for your plants.