Rhododendron advertises with picturesque names of varieties, such as gold topaz, snowstorm or fragrance cloud. In order for the popular ornamental shrub to live up to these titles, all care components must be harmoniously coordinated with one another. A balanced supply of nutrients plays an essential role in this interaction. If you want to fertilize your rhododendron properly, you should familiarize yourself with key aspects such as the right time and the appropriate dosage. Experienced gardeners usually know from painful experience how quickly an overdose can occur. It doesn’t have to come to that. In the following you will find out everything about the best rhododendron fertilizers and how to use them for splendidly flourishing ornamental shrubs with an extraordinary envy factor.

Organically fertilize rhododendrons

The trend towards organic fertilizers in the home garden continues unabated. This method of supplying nutrients is not only extremely environmentally friendly, but also pleasantly inexpensive. Choosing the next fertilizer at random could turn out to be counterproductive. In order to fertilize rhododendrons correctly, the situation is a little more differentiated. A look at the natural site conditions provides information about the specific requirements for a rhododendron fertilizer.

In the original range of Southeast Asia it rains very often. Thus, a humus layer only a few centimeters thick is sufficient for an adequate supply of water and nutrients. In the course of evolution, rhododendrons consequently developed a shallow root system with fiber roots reaching up to reach the nutritious topsoil layer. This finely balanced system for the supply of nutrients only works if the humus soil has an acidic pH value of 4.0 to 5.5. In an alkaline, calcareous substrate, the nutrients are much more strongly bound and require a deeper root system. Any rhododendron fertilizer is selected with the specific requirements of the ornamental shrub in mind.

According to the general conditions presented, the following organic fertilizers are suitable for rhododendrons:

Deciduous compost
The leaves of oak, beech and ash make an excellent organic fertilizer for rhododendrons as compost, as they develop a low pH value. The Rotte takes up to 24 months; In return, this form of nutrient supply eliminates the need to use mineral fertilizers in the long term. Since lime in any form has no place on rhododendrons, it is not added as a compost accelerator.

  • Dosage: Spread a 5 cm layer of compost every 14 days from March to July / August
  • Cost: none

Bark compost Composted bark chaff, especially from oak and conifers, has a structural stability similar to that of peat. Environmentally conscious hobby gardeners therefore favor bark compost as a helpful peat substitute, especially since it also has a lowering effect on the pH value of the soil. As the sole organic fertilizer for rhododendrons, it can be enriched with clay, lime-free rock flour and sand or perlite for permeability. In view of the years of rotting time, the purchase of bark humus is recommended for use in private ornamental gardens. It is important to consider the risk of confusion with bark mulch, which is used exclusively to cover the soil against moisture and heat loss and rather removes nutrients from the soil instead of adding them.

  • Dosage: From March to July / August, spread a 5 cm thick layer every 14 days
  • Cost: 50 liters for about 7 euros

Coniferous compost
If you have a large number of spruce and larch needles in your garden, processing them into coniferous compost is a good idea. This has a similar spectrum of activity on rhododendrons as leaf compost. In combination with garden soil, cattle manure and horn shavings, you can conjure up a valuable fertilizer for magnificent ornamental shrubs.

  • Dosage: Distribute around the bushes every 2 to 3 weeks in spring and summer
  • Cost: none

Horn shavings / horn meal An
indispensable component of organic fertilizers are the nitrogen-rich horn shavings or fine horn meal. These are shredded horns and hooves from cattle for slaughter. A single addition to the compost in spring is sufficient for the supply during the entire vegetation phase. The thicker horn shavings in particular only gradually release nutrients to the roots.

  • Dosage: Work a handful of each rhododendron superficially into the ground in March
  • Cost: 1 kilogram of quality goods from 3 euros

All efforts to properly fertilize rhododendrons fail if the pH of the soil is too high. It is therefore urgently advisable to determine this value in advance using a test set from a specialist retailer. No previous chemical knowledge is required, as a simple staining reaction will reveal the result. If the result shows a value of 7 and higher, organic rhododendron fertilizer alone is not able to lower it. If necessary, dissolve 150 grams of Epsom salt in 10 liters of rainwater and distribute the mixture over 1 square meter. The treatment lowers the pH value by one point.

Tip: Avoid deep cultivation of the soil, but only rake in rhododendron fertilizer superficially. Otherwise there is a risk of damaging the shallow root system with the delicate fiber roots.

The best organic rhododendron fertilizers on the market

Making organic fertilizer yourself in the form of a compost heap requires a suitable place in the garden and a lot of time and effort. Where these capacities are not available, rhododendron fertilizers from the trade compensate for the demand. In general, when buying fertilizers for these ornamental shrubs, you should pay attention to the following product properties:

  • lowering or neutral effect on the pH value of the soil
  • as low as possible in salts and chloride
  • rich in potassium and phosphorus
  • less nitrogen-stressed

A proportion of mycorrhiza, a symbiotic soil fungus, is advantageous. This fungus forms a close connection with the roots, from which both sides benefit. The rhododendron uses the existing nutrients better, while the mushroom is supplied with sugar and carbohydrates.

COMPO natural fertilizer with guano for rhododendrons
As a pure organic fertilizer for rhododendrons and other bog plants, this preparation contains, among other things, guano, one of the most valuable natural fertilizers of all. In addition to a targeted supply of nutrients, Compo natural fertilizer activates the microorganisms in the soil and thus promotes humus formation.

  • Dosage: 90 grams per square meter every 4 weeks from April to July / August
  • Cost: 1 kilogram from 6 euros

Neudorf Azet Rhododendron fertilizer
A sensible alternative for hobby gardeners without access to a compost heap. The organic fertilizer is composed exclusively of plant and animal ingredients as well as living microorganisms. He also involves the symbiotic fungus mycorrhiza to improve nutrient evaluation.

  • Dosage: 75 grams per square meter in April and July
  • Cost: 2.5 kilograms from 8 euros

Dehner bio-rhododendron
fertilizer with mycorrhizal fungi Among the few bio-fertilizers that can be found on the market for rhododendrons, another product has been established that also uses mycorrhizal fungi.

  • Dosage: 100 grams per square meter every 4 to 6 weeks
  • Cost: 1 kilogram from 7 euros

The best long-term rhododendron fertilizers

Those who cannot get used to the time and technical effort of organic fertilization are best off with the following mineral-organic fertilizer preparations for a month-long depot effect.

Substral Rhodovital Soil Treatment
The combination preparation acts as a fertilizer and soil additive. The soil life receives new energy and deficiency symptoms are compensated. This strengthens the resistance, so that diseases and pests have a hard time.

  • Dosage: In spring and autumn, sprinkle 200 grams per square meter over the root area
  • Cost: 1 kilogram from 10 euros

SUBSTRAL Osmocote Rhododendrons
The composition is formulated in such a way that a single application per season ensures nutrition. Each grain of fertilizer is coated so that it only releases its ingredients gradually. With increasing warmth, the degree of release increases so that all important nutrients are available exactly when they are needed most.

  • Dosage: Spread 80 grams per plant in April
  • Cost: 1 kilogram from 6 euros

COMPO long-term
fertilizer with sheep’s wool The low-chloride complete fertilizer for rhododendrons scores with sheep’s wool for a long-lasting effect for up to 5 months. The explicit initial requirement of the ornamental shrubs is quickly met in the spring. Then the long-term pearls covered with a layer of wax based on sheep’s wool are used, which gradually become active. Deficiency symptoms can therefore not even arise.

  • Dosage: Apply 100 grams per rhododendron in spring
  • Cost: 1 kilogram from 5 euros

Beckmann Rhododendron Fertilizer
The manufacturer Beckmann is bringing a medium -lasting fertilizer onto the market. The organic-mineral preparation ensures a balanced supply of nutrients for 3 months, activates the microorganisms and contributes to the formation of humus. All attributes that a lavishly blooming rhododendron desires.

  • Dosage: 100 to 120 grams per square meter from April every 3 months
  • Cost: 4 kilo sack from 13 euros

Cuxin special fertilizers for rhododendrons
hobby gardeners who are looking for a fertilizer with a primarily lowering effect on the pH value of the soil are well advised to use this special fertilizer. The preparation acidifies the soil so that the contained nutrients can be used by the plant without loss. At the same time, the fertilizer provides an extra portion of iron for a breathtaking bloom.

  • Dosage: Spread 100 grams of fine granules every 8-12 weeks in the root area
  • Cost: 1 kilogram from 5 euros

MANNA LIN rhododendron and azalea fertilizer
A real all-rounder, but one that has its price. This fertilizer does not lack any of the desired properties, such as an acidic effect, plenty of iron, little salt. Smart hobby gardeners also use MANNA LIN fertilizers for their hydrangeas, because they take on a bright blue color after use. Incidentally, the product compensates for the apparently higher price with a remarkable productivity. 1 kilogram of the water-soluble granulate is sufficient for a whopping 500 liters of irrigation water.

  • Dosage: In March and April dissolve 3 measuring spoons in 10 liters of irrigation water every 10 days
  • Cost: 1 kilogram from 10 euros

KEYZERS Rhododendron Fertilizer Hobby
gardeners who prefer premium quality products and only secondarily pay attention to the price will find what they are looking for here. The mineral-organic fertilizer preparation enjoys remarkably good reviews. This fact is primarily related to the use of only high quality ingredients. The rich fertilizer only needs to be applied twice per season due to its long-lasting effectiveness.

  • Dosage: A handful of fertilizer per ornamental shrub in April and July
  • Cost: 1 kilogram from 19.90 euros

Liquid fertilizer for rhododendrons in the bucket

Cuxin Rhododendron liquid fertilizer
Mineral components give potted plants a quick start to the season, while organic raw materials ensure the continuous effect.

  • Dosage: Concentrate weekly 5 milliliters in 1 liter of irrigation water
  • Cost: 800 milliliters from 7 euros

Chrystal liquid rhododendron
fertilizer This NPK fertilizer takes into account the need for vitamins for a splendid rhododendron bloom. It therefore not only contains nitrogen, phosphorus and potassium, but is also enriched with the Vitamin Plus system from Chrystal.

  • Dosage: 1 cap in 1 liter of water
  • Cost: 500 milliliters from 5.50 euros

If you want to fertilize your rhododendron properly, knowledge of its growth behavior is an advantage. As a shallow root, the ornamental shrub is dependent on a balanced supply of nutrients in an acidic soil. If the plant is confronted with lime or salt, growth depression inevitably sets in because the nutrients are too much bound in the soil. The best rhododendron fertilizers take these circumstances into account and add other beneficial attributes. First-class preparations have additional vitamins or contain the beneficial mycorrhizal fungi. Hobby gardeners with a tight time frame for maintenance work will appreciate special long-term fertilizers, which are usually only applied once or twice a year. Supporters of organic fertilizers favor special deciduous or coniferous compost for their rhododendrons, enriched with horn shavings for the nitrogen supply. A large variety of suitable fertilizers is therefore available that reliably prevent deficiency symptoms in rhododendrons.

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