Rhododendron is native to Japan and China. The ornamental shrub makes special demands on its soil. They resemble the requirements of azaleas and heather, because all plant species are heather plants. You need a pH value between 4.5 and 5.5, so an acidic soil. "Inkarho-Rhododendron", a very special breed, thrives on less acidic soils.
Rhododendron is an eye-catcher in the garden. There are over 1000 different varieties. Early species bloom when all other garden perennials and shrubs are still in the starting blocks, as early as spring. Others wait until June. However, rhododendrons make special demands on their plant substrate for the bright colors from white to yellow to red and purple flowers. In addition to a partially shaded place where the woody plants can develop properly, the soil should be acidic. If there is no naturally acidic soil, a soil improvement with suitable rhododendron soil can help.
What is the optimal soil for rhododendrons?
Rhododendron needs a pH value between 4.5 and 5.5. The soil should contain potassium, calcium, magnesium, iron, manganese, boron, copper and zinc. A value between 5.0 to 5.5 is found for a mixture of four percent organic matter and below
five percent clay content achieved. This concentration can be found in nature in the marshland in front of moors. The decorative rhododendron has a high need for nutrients that must be covered by regular fertilization. The plant needs a lot of water, but does not tolerate waterlogging. In addition to garden soil, special soil for rhododendrons consists of:Bark humus
Bark humus is a finely ground form of bark mulch. The humus is enriched with nitrogen and has a pH value of 5.5. It is used for soil improvement. It promotes root growth and soil activity. Bark humus is available at hardware stores.
Leaf earth
Foliage soil is made from composted leaves that are added to the composter in autumn. Then there is nitrogen and a layer of earth. The composting process takes two years. Leaf soil is slightly acidic.
sand
Sand is used to improve loam and clay soils. It ensures better ventilation and moisture drains off better. Sand has a ph value below 5.
guano
The fertilizer is 100 percent natural fertilizer. It is made up of bird droppings, natural nitrogen, natural phosphorus and rock flour. It promotes growth and soil activity. The organic fertilizer is available from specialist gardeners.
Disadvantages of purchased plant substrate
Commercially available substrate is peat
added to achieve a favorable pH value for rhododendrons. The peat extraction destroys the unique fauna and flora of the moors. Every year amateur gardeners use around two million square kilometers of peat. In the meantime, the peat not only comes from indigenous moors but is also imported from Lithuania and Estonia, for example. The destruction of the moors is spreading across Europe. The use of peat in the garden is not without controversy. Once peat has dried out, it can no longer store water. It also acidifies the soil. This releases heavy metals stored in peat, which are deposited in the soil and later taken up again by other plants. Leaf soil and composted spruce needles can be added to normal garden soil as a peat substitute.Tip: Uncomposted materials remove too much nitrogen from the soil, which the rhododendron needs itself.
Mix the substrate yourself
Bark compost, garden soil, sand in equal parts make a suitable rhododendron soil. Sand is used to improve heavy soils. Beef humus is responsible for the acidic environment. Charcoal or ash will help disinfect. Common fungal diseases can be prevented in this way. Clay granules are used to store moisture. It makes the soil looser.
Tip: Nutrient-rich humus initially meets the nutritional needs of rhododendrons. Therefore put a layer of humus in the planting hole. Excavated humus is available cheaply from civil engineering companies. Throw the excavated material through a sieve before adding it to the rhododendron soil.
Determine the pH value
The correct pH value is essential for the rhododendron to grow. The pH value must be determined so that the ingredients in the garden soil are correctly dosed. Test strips are available from specialist garden shops. In addition, you will need boiled water. For the determination, a sample of the self-mixed rhododendron earth is mixed with the sterile water to form a paste. The test strip will last for around ten
If the ph value is too low or too high, the individual ingredients must be dosed differently. Finally, mix the rhododendron soil vigorously.
The planting hole
Water the rhododendron's root ball sufficiently before planting. The planting hole must be around four times the size of the rhododendron's root ball. If the garden soil is poorly permeable, then drainage is added to the planting hole as the bottom layer. Now fill in so much plant substrate that the root ball is only about three centimeters deeper than in the seed pot in the planting hole. Rhododendrons are shallow roots. If the root necks are filled in and the root network does not get enough air, then the plants wither. Now fill in the remaining spaces with rhododendron soil and lightly step on the soil. Create a pouring rim and pour eight to twelve liters of water onto the rhododendron. Later the wood is watered weekly.
Tip: Avoid waterlogging. It leads to root rot!
frequently asked Questions
When should rhododendron soil be mixed by yourself?
If the soil is too calcareous or the pH value does not match, an excavation should be made and mixed rhododendron soil should be filled in for it.
When is rhododendron transplanted?
A good date for the new planting is in May after the ice saints. Older plants are moved in early autumn between September and November or in early spring between early March and mid-May. To do this, the branches are tied together to prevent them from breaking off.
How do I plan the space requirements for rhododendrons?
Older specimens can be up to three meters high and at least as wide. Shrubs are planted individually, but also in hedges. Small species get along well in pots and planters. There is a suitable cultivar for every space requirement.
Which location is best?
Rhododendron needs a light penumbra.