The rhododendrons also offer the gardener plenty of choice, the entire genus comprises around 1,000 species, including the azaleas. They are simply a type of rhododendrons that got their own name mainly because they have a particularly compact growth and particularly fine flowers. Of course, the rhododendrons only show these blossoms in optimal quantities when they feel comfortable in your garden, which is why it is now about the demands of the beauties.
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Earth and location for the rhododendron
Rhododendrons need acidic soil, i.e. soil with a pH value between 4 and 5.5. It is often advised to mix peat under the soil to produce this acidic soil.
peat
Any environmentally conscious gardener will initially reject this because he does not want to be involved in the destruction of one of the most biodiverse ecosystems on earth through peat extraction. However, by adding peat you are in no way creating the best soil for your rhododendrons or other bog plants: peat in a certain stage of compaction develops low pH values, but at the same time has become very poor in nutrients. And our plants, even those that like to live in acidic soil, want nutrients. Because if they originally lived in wetlands, they do so before those wetlands have turned into bogs. If bogs develop from these areas, plants such as rhododendrons will no longer be able to survive there,
It therefore seems more promising to mix substances into the rhododendron soil that not only adjust the pH value, but also bring in nutrients. There are a large number of such substances; you can get a lot of inspiration, for example, if you search for the term “peat” on the website of the Naturschutzbund Deutschland (www.nabu.de). Perhaps some of these substances are already available to you in your environment; coniferous leaves, oak leaves, sour grasses and shredded conifer bark can be used to create an acidic compost, and the addition of grape esters or coffee grounds influences the pH value in the desired direction.
However, you will only be able to change the pH of the soil slightly through this acidic compost. If you want to grow rhododendrons in very calcareous soil, it becomes a little more labor-intensive: You then have to work with specially dug and sealed or raised beds, which you completely fill with a substrate that is suitable for the pH value. Then you no longer need acidic compost, it is enough for the future if you throw oak leaves loosely under the bushes, which then slowly rot together with falling rhododendron leaves. However, today there are also varieties of rhododendrons that can withstand a little lime in the soil, i.e. a roughly neutral pH value. It is certainly the more convenient solution to use such varieties in heavily calcareous soil (or simply to grow plants,
The rhododendrons feel comfortable in a location in the shade or partial shade or shade, because they also like to be sheltered from the wind. B. can be planted well on the northwest side of the house. But you can also choose any other suitable location and surround the rhododendrons with conifers for protection.
Plant and care for rhododendrons
Rhododendrons are planted in a pit about half a meter deep, which is provided with a drainage layer at the bottom. You can add about a hand’s breadth of gravel or rubble, bark compost, kindling or other drainage materials. The functioning of the drain should be checked, rhododendrons really do not like waterlogging. Before inserting the rhododendron, you should moisten the root ball well, it is then covered with a little soil and should be well watered again.
Good irrigation of the rhododendrons is important; Particularly in warm locations where the rhododendrons get sun, you have to water them thoroughly. When the leaves curl down, the rhododendron wants to reduce evaporation, then water could already be lacking. In summer, water often has to be given every day. Evergreen rhododendrons also need to be watered in winter when it is dry and sunny for a long time (only on frost-free days).
You can fertilize your rhododendrons with any complete fertilizer whose NPK mixture is 5-4-7 or similar. If you apply the above-mentioned compost, leaves and coffee grounds, this is already an organic fertilization, which has the advantage that you can not overfertilize as quickly as when using synthetic fertilizers. But there are also organic slow release fertilizers to buy and a lot of other substances from nature that could also be introduced. The most important thing with the rhododendron seems to be that you avoid fertilizers that are enriched with lime (e.g. often with primary rock flour), otherwise it usually gets along very well with its mulch in loose soil.
Cut rhododendron
Rhododendrons can get quite large, so in many gardens they are not allowed to grow completely freely. When pruning, it should be noted that the rhododendron sets its flowers in the previous year, so it should be pruned immediately after flowering. Then he can form new flower buds over the rest of the year. But it is only cut when it becomes too big. If the cut goes inside, where it is already bare, it doesn’t matter, the rhododendron will now form new green in the places where it now receives light again. So you can cut back a rhododendron radically. The easiest way to restore an eye-catching shape is if you thin out the inside quite well, so many of the branches that have now grown quite angled can be removed, so that the rhododendron looks airy again on the inside. Immediately after the cut, the rhododendron will do well to give it plenty of water.
Propagate rhododendrons
A rhododendron can be propagated very well by cuttings, you just need to cut off a side shoot after flowering. You can and should choose a shoot that is lignified and grows close to the ground. Cut this shoot diagonally without cutting through and bend it down to the ground next to the plant (check beforehand whether the distance is right). The cut notch should lie open towards the ground, it now forms wound tissue and then roots. To do this, of course, it has to remain open, a stick in the cut helps. Either you dig in your shoot a little or you pile it up, in any case it should also be anchored in the ground with a piece of wire and tied to a rod in the upper area, then it does not have to worry about anything else new roots. For this the shoot will need at least until next spring, even then you should first “smile” carefully, whether it is already that far, maybe it will take a longer time (sometimes it should take years). When the roots are there, the shoot is separated from the mother plant and possibly moved.
You can also propagate your rhododendron by cuttings, which are also cut from woody branches from the previous year after flowering. You can then divide these cuttings into several hand-length pieces that always have a shoot knot on the lower side. The cuttings are placed in a pot with potting compost and left outside for the summer. By autumn they should have roots and can then be planted in the garden.
If you want to grow rhododendrons from seeds of your own plants, you would have to harvest them very early, when the capsules only open, you will hardly find the tiny seeds (the thick capsules are the fertilized ones). The seeds are also placed in pots with suitable potting soil and then, if possible, in an indoor greenhouse. They should be bright, but not sunny, and kept slightly moist. The seedlings should appear after about four weeks, but they will only be strong enough to prick out after about a year. And the first flower buds will appear after two years at the earliest, so you need a lot of patience to grow rhododendrons from seeds. By the way, you should always have a fungicide on hand because the seedlings tend to be attacked by fungi.
Hibernate rhododendrons
Most rhododendrons come into the garden over the winter without any help, do not be frightened when the leaves fall off, as happens with most azaleas and some other rhododendron species. Only rhododendrons in the bucket need winter protection, the potting soil freezes much faster. So you surround the pot with the usual insulating materials that are suitable as winter protection, do not forget to insulate the pot well towards the bottom. If you’ve acquired one of the few rhododendrons that come from tropical areas, you even need to get them indoors in winter.
An evergreen rhododendron also needs enough water in winter, which is also scarce in the bucket than in the garden. For watering in winter, you should always choose a mild temperature; if in doubt, do not water too much so that a frozen lump does not form the next night. Of course, it also applies to the container plant in winter dress that it needs a protected location close to the house.
Pests and diseases of the rhododendron
Actually, rhododendrons are not very well known for infestation with pests or for diseases, but incorrect site conditions can certainly lead to infestation with fungi, which should then be combated with the appropriate fungicides (a site survey is of course also pending).
If the buds look strange, maybe the rhododendron cicada was with you and transmitted the bud rot. Since it also likes to bring in a fungus, infected (brown) buds should be removed as soon as possible (disposal in household waste, not in compost). The larvae on the leaves are then controlled with a suitable pesticide.
Weevils (black weevils) may also be interested in your rhododendrons, which can be controlled with nematodes or with various pesticides.
Or the rhododendron lattice bug (Stephanitis rhododendri) introduced from Japan, which sucks out the central ribs and thereby first turns the leaves brown and then lets them fall off. The pest, which is relatively new to us, should also be able to be combated by pesticides against sucking insects on ornamental plants, but there are still few experience reports available.
The ecological benefits of the rhododendron
From an ecological point of view, rhododendrons are not the first choice, especially not in locations where they are really comfortable. Then they tend to multiply on a massive scale, as can be seen in Ireland and Great Britain, where poison, fire and bulldozers are now used throughout the country to control an overgrowth with rhododendrons.
Otherwise they are probably wrongly classified as ecologically not very valuable woody plants, numerous animals of the local fauna have adjusted to use the rhododendron as a protective and nesting wood, you can see beetles and flies, bees and bumblebees on them. However, the fruits of the rhododendron cannot ripen in our climate, so if you want to attract beneficial insects you should also establish some native woody plants in your garden, which provide food for the animal world all year round.
Conclusion
If you like to surround yourself with lush flowers in the garden, a rhododendron is an asset to the garden landscape. But not if you have a very chalky garden soil, adapting the soil causes such effort that switching to more suitable plants is probably more clever. If the soil is more or less suitable, you only have to be careful when choosing the variety that you do not accidentally catch a rhododendron with a tropical home when it is to be planted in the garden. If it is planted in a suitable soil in a location that is convenient for it, a rhododendron is pleasantly resistant to pests and diseases and overall easy to care for.
