All species of the genus Rhododendron place high demands on their location; they only thrive in acidic soil. The trade therefore offers special rhododendron soil. You can find out what you should consider when purchasing and using it and how to mix the substrate yourself in this article.
What is rhododendron soil and what is it used for?
Rhododendron soil is a special substrate with an acidic pH value that is ideal for rhododendrons and other ericaceous plants. It has a high nutrient content and contains no lime components. You can buy rhododendron soil or make it yourself by mixing leaf humus, bark compost and cattle manure pellets.
- Rhododendron soil is a special substrate mixture for rhododendrons and other ericaceous plants.
- The substrate has a high nutrient content. Another important feature is the acidic pH value, which should ideally be between 4 and 5.
- Rhododendrons and other ericaceous plants need a low-lime, loose and humus-rich substrate in order to thrive and bloom profusely. Normal garden soil with a neutral or even alkaline pH value is not suitable.
- Rhododendron soil can also be mixed yourself. This way you avoid using peat, which should no longer be used in the garden for ecological reasons.
What is rhododendron soil?
Rhododendron soil is a substrate specially mixed for the needs of rhododendrons and other ericaceous plants. It is characterized by a low pH value and a specific nutrient composition. You can use the soil both to acidify normal garden soil - for example if you want to plant rhododendrons - and to plant these attractive flowering plants in the pot.
Properties and composition
Rhododendron soil is permeable and at the same time stores moisture
The rhododendron, which originally comes from the high mountains of Asia, needs very special soil conditions so that it can grow and thrive here. Rhododendron soil completely meets these needs in its composition and structure:
- loose, airy substrate with high water storage capacity
- at the same time very well permeable, prevents waterlogging
- very high nutrient content
- mainly contains iron, potassium and calcium
- as well as the trace elements boron, copper, manganese and zinc.
- contains no lime
- acidic pH between 4 and 5
In most gardens, the appropriate conditions can only be created by adding rhododendron soil. Please note that when using it, you also acidify the surrounding soil area and can therefore only put acid-loving companion plants in the bed.
Excursus
Which plants still grow in rhododendron soil?
In addition to rhododendrons, the following plants also prefer to grow in acidic substrates and can therefore be combined very well with the flowering trees: astilbe, bergenia, marshmallow, feather bush, heuchera, hosta, camellia, kerrie, magnolia or cotoneaster. Some berry trees such as blueberries, cranberries and cranberries also thrive in this substrate.
What is rhododendron soil made of?
Rhododendron earth is composed of different ingredients, depending on the manufacturer and product. These ingredients are often found in commercially available mixtures:
- Peat
- humus soil
- Wood fibers
- Clay
- Sand
- the main nutrients nitrogen, phosphate, potassium oxide and iron sulfate
- Guano or another fertilizer
Tip
If you want to test the pH value of your garden soil before planting rhododendrons, you can easily do this using test strips (€2.00 on Amazon) from the hardware store or pharmacy. For testing, you take a small soil sample, mix it with (lime-free!) water and hold the test strip in it. Based on its color, you can finally tell whether your soil is acidic, neutral or alkaline.
Buying rhododendron soil – what you should pay attention to
There are significant differences in quality when you buy rhododendron soil
You can use rhododendron soil with or without fertilizer from various manufacturers in
- Building and garden centers
- in discount stores
- and on the Internet
buy. There are significant differences in quality between brand and discount manufacturers. Low-priced products in particular often use ingredients of lower quality, which later becomes noticeable in the growth and flowering of the plants. However, the peat content of many products is particularly problematic, as raised moor peat is an ecologically extremely questionable component.
When peat bogs are mined, not only are valuable ecosystems with rare animal and plant species irretrievably lost. Peat bogs are also important CO2 reservoirs; when they are destroyed, CO2 deposits that are millions of years old are released back into the atmosphere and thus have a negative impact on the climate. It is therefore important to pay attention to peat-free substrates, which are now available from (almost) all leading brand manufacturers. Rhododendron soil from discount stores, on the other hand, usually contains large amounts of peat, as the material can be purchased very cheaply.
Mix rhododendron soil yourself
You can find out what else rhododendron needs to feel good in this detailed and entertaining article:
NDR Mein Nachmittag – so gedeiht Rhododendron am besten
Instead of using ready-made rhododendron soil, you can mix a high-quality, peat-free substrate for your rhododendrons and other ericaceous plants yourself. For this you need these ingredients:
- Leaf humus: consists largely of rotted leaves, has a high nutrient content and a naturally low pH value; Prefer leaf compost made from oak or beech leaves
- Bark compost: low pH value, high nutrient content, coarse structure enables good aeration of the substrate and makes it nice and looseor alternatively
- Wood chip compost: as a replacement for bark compost, has similar advantages as thisor
- Needle litter: the (rotting) needles of conifers provide a low pH value
- Fertilizer: Here it is best to use well-rotted cattle dung or, if you can't get it, cattle dung pellets, alternatively a mineral rhododendron fertilizer is also very suitable
- Sand: loosens the earth
Make sure not to use bark mulch, it is too coarse and would not rot in the bed in the absence of air. However, you can use the material to cover the planting site. Conventional garden compost is also not suitable, as it usually has a pH value that is too high and often contains lime - a deadly mixture for rhododendrons.
In some recipes, guano is also added as a fertilizer. Of course, bird droppings are an excellent fertilizer, but their environmental impact is also not the best. Cattle dung is just as valuable, but ecologically harmless.
If, on the other hand, you have heavy, loamy or clayey garden soil, we recommend using additional coarse building sand. This loosens the structure slightly and ensures better drainage. Rhododendrons cannot tolerate waterlogging at all.
And this is how you mix the rhododendron soil yourself:
Take a large wheelbarrow and a shovel and mix in the wheelbarrow:
- two parts leaf compost
- two parts bark compost, wood chippings compost or composted needle litter
- two parts building sand
- two parts cattle dung pellets, alternatively rhododendron fertilizer
Excursus
Is ericaceous soil and rhododendron soil the same?
Yes, bog soil and rhododendron soil are different names for nutrient-rich plant substrates with an acidic pH value. You can use both varieties for rhododendrons as well as other plants with similar location requirements. There is only a difference between individual products: the composition can be different (peat-containing / non-peat-containing) or the nutrient content (fertilized / not fertilized).
Use rhododendron soil correctly in the garden and pots
Rhododendron soil should not be placed too deeply into the soil, because rhododendrons are shallow-rooted
“Plan farsightedly when planting rhododendrons, as these trees can grow very old and large.”
You can use the purchased or self-mixed rhododendron soil both in the garden and as a plant substrate for pots. When planting, make sure that rhododendrons are extremely shallow-rooted - so it is no use burying the substrate in the bed or sinking it into a deep planting hole. Here the rhododendrons would not be able to absorb the valuable ingredients because their roots cannot reach them.
The planting hole should only be about 40 to 50 centimeters deep, but wide enough for the spreading roots. It is better to distribute the excavated soil elsewhere in the garden, at least if it is soil with a pH value above 5. Instead, fill in the rhododendron soil. If necessary, you can dig the planting hole a little deeper and fill in an additional drainage layer. This makes sense if the soil at this location is heavy and impermeable to water.
This diagram shows you how to properly create a moor bed:
In the plant pot, however, you do not need any additional additions, as the finished rhododendron soil alone is sufficient. However, please make sure that if the substrate has already been pre-fertilized, you do not need to add any additional fertilizer for the next six to eight weeks.
Frequently asked questions
When is the best time to plant rhododendrons?
As with other trees, the best time to plant rhododendrons is autumn. Ideally, you can plant the attractive shrubs in the garden between the beginning of September and mid-November at the latest. But planting is still possible in spring, the weeks between the beginning of March and mid-May are ideal - of course only if there is no frost and the ground is not frozen.
Where do rhododendrons thrive particularly well?
Rhododendrons primarily need loose, very humus- and nutrient-rich and, above all, acidic soil. In terms of their light requirements, the trees generally tolerate shade, but bloom more profusely with more light. Therefore, plant them in a location that is as bright as possible, but that is at least shaded during midday. Rhododendron is very suitable as an underplant for taller trees, as long as it is not too dark there.
Can I plant rhododendrons in normal garden soil?
In principle, you can also plant rhododendrons in normal garden soil as long as you follow the following tips:
- bright, shady location
- Garden soil with a pH value that is as acidic as possible
- If this does not have an acidic pH value, add rhododendron soil or leaf humus
- Dig the planting hole over a wide area and replace the excavation with a suitable substrate
- Planting rhododendrons together with conifers
In the long term, the tree cannot tolerate pH-neutral or even alkaline garden soil and is likely to die sooner or later without appropriate measures. An exception are new, lime-tolerant INKARHO varieties. These also thrive in normal garden soil and no longer necessarily need an acidic substrate.
Tip
So that the rhododendron grows he althily and blooms profusely, you should supply it with a special rhododendron fertilizer twice a year. This not only provides the necessary nutrients, but also keeps the pH of the soil low.
