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In order for the rhododendron to develop its flowers fully, it needs the right nutrients. We give you tips on how to fertilize rhododendrons correctly.
The rhododendron (Rhododendron) is a genus of shrubs from the heath family (Ericaceaea). In nature, the genus grows primarily in acidic locations with a very permeable subsoil. And the fertilization should also be adapted to these special conditions. We tell you how you can create the perfect conditions in your home garden and which fertilizers are particularly suitable for your rhododendron.
Rhododendrons are adapted to an acidic, humus-rich and well-drained substrate. Deficiency symptoms are very often observed in them, especially yellow leaves. In many cases, the reason for this is a nutrient deficiency: nitrogen, iron or magnesium deficiency can lead to yellow leaves on rhododendrons. To remedy this, however, it is not always enough to just distribute iron fertilizer for rhododendrons, because the pH value of the soil in which the plant grows must also be taken into account. If the value is above 5, i.e. it is no longer nice and acidic, the acid-loving plant is less able to take up iron efficiently - even if there is enough iron in the soil. That is why it is particularly relevant to ensure the acidification of the soil when planting the rhododendron.
If the soil is then acidic enough, you can fertilize your rhododendron so that it shines particularly brightly - we will explain the important ones to you below Questions about fertilizing popular shrubs.
When should you fertilize rhododendrons?
For most rhododendrons it is sufficient if they receive a reserve fertilization once a year, however it is important when you fertilize rhododendrons. An organic long-term fertilizer such as our Plantura organic flower fertilizer, which releases its nutrients over a long period of time, is also best suited for this. The best time to fertilize is late spring between mid-April and mid-May. One should be later than mid-JuneRhododendrons should then no longer be fertilized in order not to endanger the frost hardiness. If you want particularly lush growth, you can also apply two fertilizations at the beginning and end of early summer, but one fertilization is sufficient for the he alth of the shrub. In special weather conditions or unfavorable site conditions, a second fertilization in early summer can also make sense. You should consider this, especially after the rainy spring months. By then it may be that the nutrients have already been washed out and the soil is depleted.
Summary: When to Fertilize Rhododendrons?
- One fertilization a year with a mainly organic long-term fertilizer is sufficient.
- The ideal time is between April and May.
- A second fertilization can be done in early summer.
- Fertilization is no longer useful after mid-June.
The right fertilizer for rhododendrons
Moorbed plants like the rhododendron have shallow roots and love moderately nutrient-rich, humus-rich and well-drained soil with an acidic pH value between 5 and 6. This is because rhododendrons come from the acidic granite rocks of the Himalayas. To mimic these conditions, rhododendrons are almost always planted in acid peat in this country. Although this suits the soil preferences of the rhododendrons, peat is very low in iron and magnesium and generally low in nutrients. A good fertilizer for rhododendrons provides the plant with the necessary nutrients and, above all, brings the two micronutrients magnesium and iron with it. In addition, the plants are mostly flat-rooted, which is particularly advantageous on slightly calcareous soils. If you don't find the ideal conditions in your garden, you can help with targeted fertilization. You only have to do this in the upper layers of soil through which the rhododendron has rooted. In the following we will tell you how and with what you can best fertilize your rhododendron.
Fertilize rhododendron organically
Organic fertilization has some advantages over the mineral variant - not only for rhododendrons. While it doesn't work as quickly in the short term, it's a more sustainable choice in the long run. The following applies to rhododendrons: you should use pH-lowering fertilizers orat least those that do not affect the pH value. Fertilizing with compost is not necessarily recommended, because compost is very variable in its properties and often even has a rather high pH value. Fertilizing rhododendrons with horse manure is a better option because horse manure is rich in magnesium and iron. However, composted horse manure should be used here, since fresh horse manure is far too rich in nutrients.
If you do not have access to such natural fertilizers or want to do without animal components in the fertilizer, you can use long-term organic fertilizers. This includes our primarily organic Plantura organic hydrangea fertilizer. This not only has the advantage of a long-lasting effect, but also provides rhododendrons and other ericaceous plants with exactly what they often lack: iron and magnesium. It is also much better for the soil life in your garden. Hydrangeas, blueberries, cranberries, skimmia, heather and lavender heather can also be fertilized as needed with our hydrangea fertilizer. Of course, our iron fertilizer for rhododendrons is safe for children, pets and garden animals. Below we have put together instructions for you on how to optimally fertilize your rhododendron organically.
Organic long-term fertilization: application recommendation for rhododendrons
- Before planting, work 100 - 150 g/m² (about a large drinking glass full) of our Plantura organic flower fertilizer into the top soil layer.
- Dig a wide planting hole and loosen it deeply. Water the soil and freshly planted rhododendrons well so that the granulate can be easily loosened.
- For maintenance fertilization in spring and summer you should fertilize another 80 - 120 g/m² (0.2 liter glass) per plant.
- Push the mulch layer on the roots of the rhododendron aside, spread the fertilizer and water well. Do not work this in, however, as the flat roots of the rhododendron should not be damaged.
- As the rhododendron grows, the amount of fertilizer can be gradually increased to around 400 grams of our Plantura organic flower fertilizer in order to maintain the vitality of the plant even in old age
Tip: Feel free to be generous when it comes to distributing the fertilizer over the surface of the rhododendron. Due to its shallow, sprawling roots, the rhododendron can also absorb nutrients far away from the trunk. So distribute theFertilize within a 1.5 to 2 meter radius of your plant.
Rhododendron mineral fertilizer
In many areas, mineral fertilization offers a good opportunity to quickly intervene in the nutrient supply of our garden plants, especially when there are acute nutrient deficiencies. While mineral rhododendron fertilizers are well suited for short-term intervention, they often do not work as long-term depot fertilizers. This means that blue grain and other mineral fertilizers need to be applied at shorter intervals than organic fertilizers. Because stock fertilization is not possible unless special and expensive depot fertilizers are used. Mineral fertilizers can even damage your rhododendron, because an incorrect dose of mineral fertilizer can easily lead to over-fertilization, which in the best case only makes it susceptible to pests and frost. In the worst case, the so-called exosmosis at the roots can cause even more severe damage to the plant. It is particularly important when using mineral rhododendron fertilizers to always water sufficiently to dilute high nutrient concentrations. However, iron fertilizers for rhododendrons are usually mineral, since iron is hardly present in most organic materials - our predominantly organic Plantura organic hydrangea fertilizer is also supplemented with iron sulphate. It dissolves well in the soil solution, slightly acidifying it to improve absorption.
It is best to use a gentle but effective variant for plants and the environment and use an organic fertilizer that replenishes the iron and magnesium reserves of the soil either naturally or through a supplement.
Tip: You can also use organic or mineral fertilizers for rhododendrons that have been planted in a tub. However, due to the limited soil volume, nutrients cannot be stored well, which is why two doses per year are recommended in any case. Organic fertilization makes a lot of sense, especially in the bucket, because mineral fertilizers do not bring in all the essential nutrients and also ensure in the long term that the potting soil sags. Organic fertilizers such as our Plantura organic hydrangea fertilizer are simply spread under the mulch layer, poured on and then covered again. You should give these nutrient bombs in small doses from April to mid-June. When fertilizing your rhododendron, 70 grams per square meter and season is recommended. Alternatively, you can dissolve five grams of blue grain per ten liters of water and yourFertilize potted rhododendrons with it once a week. If you use mineral fertilizers, you should always give them with enough water to avoid harmful s alt concentrations in the small container so that the nutrients can be absorbed and burns are avoided. Mineral fertilized rhododendrons should also be repotted regularly in order to supplement important trace nutrients with new soil. However, over-watering immediately after fertilization can also flush nutrients out of the root zone of shallow-rooted rhododendrons, making them unavailable.
Fertilize rhododendron with coffee grounds
Coffee grounds are a daily occurrence in almost every household. With a pH value of around 6.5, however, it does not meet the needs of rhododendrons because it is not acidic enough. However, only a few people know that after watering it can also be used to fertilize plants such as rhododendrons. The slightly acidic properties of coffee grounds can be used to lower soil pH. However, in small amounts, the coffee grounds provide beneficial nutrients that are released when worked on the surface over a long period of time, and also increase the organic matter content of the soil, keeping it loose. When fertilizing with coffee grounds, proceed as follows:
- Dry coffee grounds.
- Scatter the coffee grounds in the root area under the mulch layer.
- But don't incorporate this one.
- Water well.
- Alternatively, you can also put the coffee grounds directly into the irrigation water and distribute them. With bedding rhododendrons you can reach for coffee grounds up to four times a year. In a pot culture, it is best to fertilize once in April and mid-June.
Do you not yet have a rhododendron in your garden and are you looking for a suitable variety or do you want to expand your stock? We introduce you to the most beautiful rhododendron species and varieties.