Fertilizing tomatoes: when, how & with what?

When are tomatoes fertilized? How often is tomato fertilization necessary? We reveal everything you need to know about the correct fertilization of tomatoes.

The tomato grown in almost every kitchen garden (Solanum lycopersicum) has a high need for nutrients and therefore also fertilizers. In order to ensure healthy growth and to be able to harvest abundantly from your tomato plants, you should therefore fertilize regularly in the growing season. But when exactly should you fertilize your tomatoes? Which fertilizer do you use and how do you apply it correctly? We will get to the bottom of these questions in this article.

Why do you need to fertilize tomatoes?

Compared to many other vegetables, tomatoes generally have a high nutritional requirement. They are therefore also referred to as heavy consumers. Nutrient-rich potting soil is therefore usually not enough for the nutrient-hungry tomatoes and, at the latest, as soon as the fruits are formed, symptoms of deficiency can also be recognized. In order to keep tomatoes and other heavy eaters healthy and to encourage them to have a high fruit yield, the nightshade plants should therefore be additionally fertilized.

When and how often should you fertilize tomatoes?

How often you need to fertilize tomatoes depends on the stage of the plant, the soil available and the type of fertilizer. The nutritional needs of tomatoes change depending on the stage of development:

• From sowing to pricking, the seedlings feed on the supplies from the seeds - during this time they do not need any fertilization.
• Young plants before planting out in May benefit from one or two small amounts of fertilizer.
• When planting tomatoes, a good basic supply of nutrients in the form of a slow release fertilizer should be mixed into the soil.
• During the season through September you should regularly top up important nutrients.

Tomato seedlings initially draw completely from their reserves from the seed. Fertilization is not only superfluous, but rather damages the tender seedlings at this stage, because the many unused nutrients can damage the root system. In return, you benefit from a low-nutrient sowing soil like our Plantura Organic herb & sowing soil. The low salt content makes germination easier.

After pricking the tomato seedlings in nutrient-rich potting soil or specially adapted tomato soil - like our Plantura Organic tomato & vegetable soil - The plants initially feed on the earth's own nutrients. However, it will still take a few weeks before planting out and it is worth fertilizing the young tomato plants. It is sufficient to apply it once or twice. At this stage we recommend using a gentle organic liquid fertilizer. It is simply spread via the irrigation water and, thanks to the nitrogen content, ensures good growth and strong green foliage.

Tip: Detailed instructions for that Sowing tomatoes as well as for that Pricking tomatoes can be found in our special articles.

When planting out, the time has come to properly fertilize your tomatoes for the first time. Depending on the weather, planting can be done in the greenhouse from mid-April to early May or outdoors from mid-May. When planting, you bring the fertilizer directly into the planting hole. Long-term fertilizers, like our mainly organic one Plantura organic tomato fertilizer, release their nutrients slowly and therefore gently for the soil and plant roots.

Fertilize tomatoes in the pot properly

Tomatoes in the pot naturally need just as many nutrients as their counterparts in the bed, but they have a much smaller volume of soil available. The roots therefore only have a limited opportunity to spread out in the pot and tap nutrients. For this reason, they usually have to be fertilized more often. A long-term fertilizer should already be mixed into the soil for planting in order to provide the plant with good nutrients in the first few weeks. The incorporation of granules in the pot later turns out to be difficult, which is why organic liquid fertilizers for tomatoes are an ideal alternative. Our Plantura organic tomato & vegetable fertilizer can be easily spread over the irrigation water. From June, i.e. as soon as the flowers and fruit start to develop, fertilize with organic liquid fertilizer about once a week. 15 to 25 ml of fertilizer are added to 5 liters of irrigation water, mixed and then poured.

Fertilize tomatoes in the pot - the right time:

• To plant the tomatoes, mix long-term fertilizers into the potting soil.
• From June you should fertilize with organic liquid fertilizer about once a week over the irrigation water.

Fertilize tomatoes in the bed

In the bed, it is a little easier to provide the tomatoes with nutrients. Ripe compost or a predominantly organic tomato fertilizer with a long-term effect - like ours - is immediately planted out Plantura organic tomato fertilizer - mixed into the excavated earth of the planting hole. With 120 to 230 grams of our potassium-rich granulate fertilizer, a tomato plant is nourished for a whole season. Between 70 and 150 grams are given when planting and the remaining 50 to 80 grams after around two months. To do this, the recommended amount is raked into the surface of the soil - but be careful not to damage the roots of the tomatoes. A 1.5 kg litter pack of our granulate fertilizer is sufficient for up to 20 tomato plants, depending on the variety.

In addition to a gentle release of nutrients, mainly organic long-term fertilizers also have positive effects on soil life and act in contrast to most of them mineral fertilizers environmentally friendly. Mineral based fertilizers like Blue grain and Co. each only provide a short but strong nutrient boost. In the long run, however, they are not enough for the heavily eating tomatoes and can strongly stimulate vegetative growth, which may increase susceptibility to disease. During heavy watering or heavy rain, the water-soluble minerals are quickly washed out and ultimately end up in the groundwater instead of in the plant.

Fertilize tomatoes in the bed - the right time:

• The first fertilization should take place during the transplanting of the tomato plants by adding slow release fertilizer to the planting hole.
• After about 2 months, fertilizing with the slow release fertilizer should be repeated again.

Tip: Vegetable broths, like Nettle manure, can have a supportive and plant-strengthening effect thanks to their numerous ingredients.

Recognize nutritional deficiencies in tomatoes

Nutrient deficiencies in tomatoes usually manifest themselves in the form of leaf discoloration:

• Nitrogen (N): If there is a lack of nitrogen, the older leaves first turn yellow, later brown and finally fall off. The young, upper leaves are still green for a long time until the deficiency takes over. In general, the plant looks rather pale green, grows poorly and hardly forms new shoots.
• Potassium (K): On the other hand, potassium deficiency manifests itself in the form of tissue that becomes brown and dry on the leaf edges. Eventually the desiccation moves between the leaf veins, while the veins still remain green. Whole leaves can dry out in this way without being due to a lack of water.
• Phosphorus (P): If there is a lack of phosphorus, the tomato plant reacts with a purple color of the older leaves, initially on the underside of the leaf, later globally.
• Calcium (Ca): Another important nutrient is calcium (Ca), as it is partly responsible for the stability of the cell walls. Typically, calcium deficiency shows up on the basis of the dreaded Flower end rot. Lime with a high calcium content can be given for planting and two months later for fruiting Tomato damage impede.

Over-fertilized tomatoes: what to do?

Over-fertilization of tomatoes is the result of excessive nutrients, mostly from quick-dissolving mineral fertilizers. Over-fertilized tomatoes react, depending on the nutrient element, with burned roots, excess leaf and Shoot growth, stunted growth or stunted growth, which lead to increased sensitivity to disease can. The fruit quality also quickly suffers from over-fertilization. In an acute case, the only thing that can help here is moving the plant into fresh soil. Excess nitrogen can also be bound in the long term with mulch materials that are difficult to decompose, such as wood chips or straw.

As a preventive measure, you should have a soil analysis carried out at the location to determine how the nutrient stocks are doing. A site-adapted fertilization is essential for outdoor and greenhouse tomatoes in order to maintain long-term soil health and fertility. Of the Soil pH also provides information on how to fertilize. When fertilizing tomatoes in pots and outdoors, you should never exceed the fertilization recommendations given.

In addition to fertilizing, there are other care measures that tomatoes benefit immensely from as they grow. In our article on the Pouring and mulching tomatoes learn more about it.