Water-soluble & available
Phosphate and potassium oxide are declared water-soluble. Add the measured concentrate to water and mix thoroughly.
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- NPK concentrate for rhododendrons and azaleas
- For root and foliar feeding
- Product-specific dilution calculator
Feed rhododendrons and understand their root zone
Rhododendrons and azaleas belong to the genus Rhododendron. Their shallow, fine roots are sensitive to drought and oxygen shortage. Evergreen and deciduous forms differ.
- Declared NPK
- 2.5 + 4.0 + 6.0With declared trace nutrients.
- Dilution
- 5 ml per 2.5 l of waterEvery 2–3 weeks during the growing season.
- Application
- Roots & foliageDilute with water before use.
- Regular application period
- April/May–SeptemberApply only during active growth.
Product information
Application & dosageMix and apply to suit the growth stage.
Application in one place
Measure. Mix. Apply.
Dilution calculator · rhododendrons and azaleas
Dilution: 5 ml per 2.5 l of water.
Your water amountRough watering-volume guide
2.5 l
Matching concentrate amount
5 ml
1 capful = 5 ml. Use a suitable measuring aid for smaller partial amounts.
Enter a water amount from 0.1 to 1,000 litres.
Use the water volume actually needed. Plant height alone does not provide a reliable watering volume.
How the guide is calculated
Concentrate (ml) = water (l) × 5 ÷ 2.5.
Prepare a clean container
Use a clean watering can or sprayer; preferably low-lime water or rainwater at 15–25 °C.
Calculate the amount
Enter the water volume actually needed. Check root-ball moisture and drainage before watering.
Add some water first
Start by filling the container with part of the chosen water volume.
Shake & measure
Shake the bottle. 1 capful = 5 ml; use a measuring aid for smaller partial amounts.
Add the concentrate
Add the calculated amount of concentrate to the water.
Top up & mix well
Top up to the chosen water volume and mix well. Watering or spraying: see below.
When to feed? 5 ml per 2.5 l of water. Every 2–3 weeks during the growing season. Regular application period: April/May–September.
Watering · through the roots
Moisten the root ball first, then distribute the mixture evenly through the root zone. Ensure free drainage in pots and check soil moisture in borders. Do not feed dry or waterlogged roots.
Spraying · onto the leaves
Spray the diluted solution finely onto leaves, avoiding open flowers. Do not apply in sunshine; account for root and foliar applications together.
Characteristics & pack sizesThe concentrate and pack sizes at a glance.
Net mass: 281 g for 250 ml; 1125 g for 1 litre.
The dilution is the same for both pack sizes.
| Pack size | Price | Yield at label dilution |
|---|---|---|
| 250 ml | 9.85 € Unit price ( 39.40 €/ l) | 125.0 l |
| 500 ml – twin pack (2 × 250 ml) | 18.95 € Unit price ( 37.90 €/ l) | 250.0 l |
| 1 litre | 29.95 € Unit price ( 29.95 €/ l) | 500.0 l |
Yield at the labelled standard dilution; account for pack size and existing nutrients.
Does this fertiliser suit your plant?
Identify your plant
For rhododendrons and azaleas; consider the actual species and growing conditions.
Use during growth
Use during active growth when additional nutrients are needed; account for pre-fertilisation and previous applications.
Consider the root zone
Account for fertiliser in fresh compost after repotting. Begin extra feeding according to need and existing nutrients.
Beyond NPK · understand the formulation
Well mixed – available to leaves and roots
The concentrate supplies declared major and trace nutrients. At the correct dilution it can be applied through the root zone or foliage.
Protected trace nutrients
Copper, iron, manganese and zinc are declared as EDTA chelates. This binding helps keep these trace nutrients available in solution.
Reduce hard-water effects
Prefer low-lime water or rainwater at 15–25 °C for mixing. Assess the actual soil reaction separately.
Measure accurately and feed to need
The label dilution applies to watering and spraying. More concentrate cannot replace suitable growing conditions.
Nutrients and plant development
Nitrogen contributes to chlorophyll and proteins, phosphorus to energy transfer and potassium to water regulation. Growth also depends on light, water and healthy roots.
Copper, iron, manganese and zinc are declared as EDTA chelates. Product pH 6.8 describes the concentrate, not a guaranteed soil pH.
Use clean, suitable watering or spraying equipment. Measure the water and calculated concentrate quantity carefully.
Products
Use other care products according to their own instructions. A product recommendation does not confirm tank mixing.
Do not mix undiluted concentrates. Follow each product’s own application method and dose.
Nutrient composition · NPKDeclared nutrients and their forms.
Declared nutrient percentages. Product pH: 6.8.
- 2.5% total nitrogen (N)
- 2% urea nitrogen
- 4% water-soluble phosphate (P₂O₅)
- 6% water-soluble potassium oxide (K₂O)
- 0.005% boron (B)
- 0.002% copper (Cu) · EDTA chelate
- 0.03% iron (Fe) · EDTA chelate
- 0.006% manganese (Mn) · EDTA chelate
- 0.0005% molybdenum (Mo)
- 0.002% zinc (Zn) · EDTA chelate
GREEN24 · Plant knowledge
Rhododendrons and azaleas through the seasons
Flowering time, leaf size and winter foliage vary by species and cultivar. Care must suit the actual garden form or indoor azalea.
Leaves and flowers
The photograph shows Rhododendron catawbiense as an example of an evergreen species.
Sten Porse · Source · CC BY-SA 3.0
Unaltered original; display without cropping.
Flowers with their own character
Flowering time and colour vary by species and cultivar.
Chrumps · Source · CC BY-SA 3.0
Unaltered original; display without cropping.
Observe bud development
Consider flower buds when pruning; more fertiliser does not guarantee extra blooms.
El Grafo · Source · CC BY-SA 4.0
Unaltered original; display without cropping.
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Growth & nutrient uptake
Leaves use light; roots take up water and mineral nutrients. The diagrams show how plant organs work together and how nutrients are absorbed.
From shallow roots to leaves and buds
Roots · absorb and anchorFine, shallow roots take up water and dissolved nutrients.
Do not cultivate deeply around shallow roots. Humus-rich, acidic, aerated soil and even moisture support the root zone; avoid waterlogging.
Shoots · support & connectWoody branches carry leaves and terminal buds.
Heavy or late pruning can remove flower buds already formed. Plan pruning according to species and cultivar.
Leaves · capture energySimple leaves use light to make sugars; winter foliage depends on species.
Yellow leaves with green veins warrant checking soil reaction, water and roots. This alone does not identify a specific deficiency or justify a higher dose.
Flowers · development & diversityDepending on species and cultivar, flowers appear singly or in conspicuous clusters.
Flowering also depends on bud formation, light, frost and pruning. Avoid open flowers when spraying; a stronger solution does not guarantee more blooms.
How nutrients enter your rhododendrons and azaleas
Select a point in the picture or choose a stage.
Stage 01 / 04
The solution reaches the root ball
Apply the diluted mixture to the previously moistened root zone. Wet the root ball evenly without leaving water standing in an outer pot.
Good to knowAssess wilting through root-ball moisture and root health before increasing fertiliser.
A closer look
The first step is contact between dissolved nutrients and root regions capable of uptake. The diagram shows this function, not a species-specific tissue section. Assess wilting through root-ball moisture and root health before increasing fertiliser.
Stage 02 / 04
Uptake at the fine roots
Fine roots and root hairs contact the soil or growing medium. Dissolved nutrients enter root cells through regulated processes.
Good to knowFresh compost and existing soil reserves already contribute to the nutrition of your rhododendrons and azaleas.
A closer look
Root hairs increase the contact area. Transport across cell membranes is distinct from water movement alone. Fresh compost and existing soil reserves already contribute to the nutrition of your rhododendrons and azaleas.
Stage 03 / 04
Root cells regulate uptake
Cell membranes and transport proteins regulate the entry of dissolved nutrients. These processes are distinct from water moving through the plant.
Good to knowA stronger concentration cannot replace healthy roots or adequate rooting space.
A closer look
Controlled processes within living root cells lie between the surface and the conducting tissue. Functional blocks do not depict the entire root anatomy. A stronger concentration cannot replace healthy roots or adequate rooting space.
Stage 04 / 04
Onwards to shoots and leaves
After uptake, water and nutrients pass through conducting tissue to aerial plant parts. Growing conditions influence development.
Good to knowConducting tissue connects roots and new shoots. Development also depends on growing conditions.
A closer look
Xylem transports water and dissolved substances. Root health and growing conditions affect transport; leaf colour alone does not establish nutrient status.
Stage 01 / 04
The solution wets the leaves
Apply the diluted mixture finely to the leaves. Avoid open flowers; they are not the target of foliar feeding.
Good to knowCount foliar applications within the shared feeding plan, not automatically on top of a full root application.
A closer look
The leaf surface must contact the diluted solution. Wetting is the first step, not evidence that nutrients have already been absorbed. Count foliar applications within the shared feeding plan, not automatically on top of a full root application.
Stage 02 / 04
Across the leaf surface
The leaf blade has a protective surface. Dissolved nutrients can cross it; leaf age and application conditions affect uptake.
Good to knowLeaf or plant size alone does not justify a higher concentration.
A closer look
Nutrients can cross the protective cuticle; stomatal routes may contribute depending on conditions. The illustration is a functional diagram, not a species-specific tissue section.
Stage 03 / 04
Use by living leaf cells
Nutrients that have entered the leaf can be absorbed by its cells and used in metabolism. A visible droplet alone is not evidence of uptake.
Good to knowYellowing leaves have several possible causes. Also check soil reaction, watering and roots.
A closer look
After crossing the surface, nutrients can be taken up by living leaf cells. Quantity also depends on the nutrient and surrounding conditions. Yellowing leaves have several possible causes. Also check soil reaction, watering and roots.
Stage 04 / 04
Use and possible redistribution
Redistribution depends on the nutrient and plant condition. Foliar feeding does not guarantee a particular growth rate or flowering.
Good to knowFoliar feeding does not replace healthy roots or checks of light and water.
A closer look
Whether and how far nutrients are redistributed from a leaf varies by nutrient. This does not establish immediate feeding of the whole plant.
Development influences requirements
Distinguish establishment, growth and dormancy
Young plants and establishment
For young plants, first check moisture, planting depth and roots. Feed according to need and the product label.
Leaf growth and bud formation
During active growth, assess demand together with soil reserves and pre-fertilisation. Feeding does not replace a suitable soil reaction.
Dormancy and winter care
Do not feed routinely during dormancy. Evergreen garden forms still lose water in winter; check moisture in frost-free weather. Assess deciduous azaleas separately.
Consider species, growth stage, root condition and existing nutrient supply together. Plant height alone does not determine the dose.
Application & calculator →Growing conditions & care problems
Adapt care to the growing conditions and stage of growth. If you notice changes, check light, water and roots first — then take targeted action.
Site and growing conditions for rhododendrons and azaleas
Pots · moisture and rooting space
A sufficiently large container needs clear drainage holes. Water evenly as needed without keeping the root ball saturated; check moisture before watering again.
Borders · account for soil reserves
Protect shallow roots from drying without burying the root collar. More fertiliser alone cannot correct unsuitable soil.
Winter · consider the species’ rhythm
Winter foliage and hardiness differ between species. Protect container roots and check moisture in frost-free weather.
Repotting & pruning · match the species
Do not plant deeper than before. Use suitable acidic soil, ensure drainage holes and account for pre-fertilisation. Consider flower buds when pruning.
What is changing on your rhododendron?
Assess chlorosis
Yellow areas between green veins can occur at unsuitable pH. Check soil and irrigation water rather than simply feeding more strongly.
Inspect feeding damage and buds
Scalloped leaf edges can indicate vine weevil. Inspect leaf undersides, buds and, if growth declines, the roots.
Investigate wilting shoots
With sudden shoot wilt, assess moisture and drainage first. Root or shoot diseases require a separate diagnosis.
Advice for your rhododendrons and azaleas
These details help assess growing conditions, root problems or a possible infestation:
- Photographs of the whole plant, affected leaves/needles, shoots and root zone.
- Species/cultivar, garden or container, light, substrate and planting date.
- Timeline, moisture, frost and previous fertilisers or care products.
Chlorosis can be associated with unsuitable soil pH or damaged roots. Have leaf spots and bud problems identified; adding more fertiliser is not a diagnosis.
PLANTS A–Z
Rhododendron and Azalea Fertiliser in the plant guide
Explore position, root space and care for the actual plant species.
View the plant guide
PRACTICAL ADVICE
What limits plant growth
Consider light, water, root space and nutrients together. More fertiliser cannot solve every care problem.
Read the guide
Quality products
Horticultural expertise
Our own production
Made in GermanyGREEN24's own products
Quick answers before you buy (FAQ)
How far do the pack sizes go?
At standard strength, 250 ml makes 125 litres, the twin pack 250 litres and 1 litre of concentrate 500 litres of prepared feed.
Does the product pH set my soil pH?
The product pH on the label describes the concentrate. It does not guarantee a particular soil pH or the pH of diluted feed. Assess compost and irrigation water separately.
When is further feeding useful?
During active growth when existing nutrition needs supplementing. Account for pre-fertilised compost and other feeds.
Which compost goes with it?
Acidic compost for ericaceous plants. Account for its initial fertiliser and review further feeding after the period stated on the bag.
Will more feed solve care problems?
Assess yellowing between green veins, brown buds and feeding damage separately. Soil pH, roots and leaf undersides give more useful clues than an extra dose of fertiliser.
Safety and storage
Safety instructions
SDS – Safety data sheet available on request.
- Do not use undiluted. Shake well before use.
- Keep out of reach of children and animals.
- Preferably use low-lime water or rainwater at 15–25 °C.
- Do not apply in direct sunlight or at temperatures below 5 °C or above 30 °C.
- Apply to a pre-moistened root zone or spray the foliage. Do not spray open flowers.
Official advisory recommendations take precedence.
Wash your face and hands thoroughly. Use diluted fertiliser promptly and keep it out of water bodies and wastewater.
Product GPSR safety information
The original leaflet supplements the product labels. The calculator uses only the verified product dilution and the actual water volume selected.
Storage
Storage & product quality
Dry · dark · above 8 °C to a maximum of 38 °C Store in a dry, dark place above 8 °C and at no more than 38 °C. Keep out of reach of children and animals.
Keep tightly closed in the original container, separate from food and animal feed.
Dry · dark · above 8 °C to a maximum of 38 °C Store in a dry, dark place above 8 °C and at no more than 38 °C. Keep out of reach of children and animals.
Do not allow fertiliser residues or rinsing water to enter waterways or wastewater. Follow the disposal instructions on the packaging.
Measure concentrate accurately and apply only after dilution. More fertiliser does not compensate for insufficient light, drought or damaged roots.
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