Oleander (Nerium oleander) is a flowering shrub. It contains chemicals called toxic cardiac glycosides that can cause death if consumed. Despite this danger, oleander seeds and leaves are used to make medicines. For lush blooms, it is essential to provide oleander with the right amount of nutrients. In order for these attractive flowers to shine in harmonious shades of white, yellow and pink-red all summer long, they need more than just warmth and sun. To help you know how to increase the number and size of your oleander blooms, we’ll explain when, what and how often to fertilize your oleander.
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Fertilize oleander – When is the right time?
Fertilize oleander when planting: you can provide your green favorite with plenty of nutrients when planting or repotting your oleander. To do this, mix mature compost or another organic slow-release fertilizer into the soil you are using. Additional enrichment with rock flour will also provide your oleander with all the essential trace elements and a load of lime, which will ensure the correct soil pH between 5.8 and 7.0. After repotting or planting, you should not use the fertilizer again for at least six weeks.
From spring (March/April) until the end of August, fertilize regularly every 1 – 2 weeks; if using an organic slow-release fertilizer, a single fertilization in spring and another in early summer is sufficient
Autumn fertilization in August with potash fertilizer for better winter hardiness.
How should you prune oleander ? You can find out here !
What are the symptoms of deficiency
If the otherwise evergreen leaves of your oleander turn yellow and fall off, it may be due to deficiency symptoms such as lack of water or nutrients. However, it may also be part of the oleander’s normal life cycle, as the leaves only live for two years and then say goodbye. Before that, all the nutrients contained in the leaf are released to the plant. Therefore, the yellow discoloration occurs before the leaves are shed. So you should only worry about your oleander if a lot of leaves are shed in a short period of time. The way the leaves change color before they drop can also help you find the cause. Pale leaves with visible leaf veins and a lack of or poor flowering indicate a nutrient deficiency.
Here, an emergency fertilization with mineral fertilizer helps. This is more readily available than the organic variety, which is an advantage in quickly combating deficiency symptoms. However, make sure that the application of highly concentrated mineral fertilizer does not lead to overfertilization due to the deficiency. Often, inadequate nutrients are not due to inadequate fertilization, but to improper soil pH. This, in turn, can be due to the use of very soft irrigation water or acidic nutrient sources such as ammonium fertilizers or coffee grounds. These lower the pH in the soil, limiting the availability of nutrients. This can be remedied by repotting, watering with hard tap water or fertilizing with lime, rock flour or eggshells.
How to properly care for oleander as a houseplant? You can read about it here !
With what nutrients should be provided oleander
Special fertilizers for oleander or Mediterranean plants are available in specialized stores. In addition to the important main nutrients nitrogen, potassium and phosphate, these also contain trace elements such as magnesium, boron, copper, iron, manganese, molybdenum and zinc. Especially in pot culture, these minerals are quickly depleted due to the low storage capacity of the soil and the highly draining nature of the oleander. However, you can use any other flower fertilizer. If important trace elements and minerals are missing from the fertilizer, you can add rock flour. Also, be sure to avoid fertilizers that are very high in nitrogen so that your oleander focuses its energy on lush blooming rather than excessive height growth.
Especially when growing in containers, it’s important to think about more than just the usual macronutrients like nitrogen, phosphate and potassium. Since oleander is one of the highly nutritious plants, trace elements such as iron, magnesium and calcium should also be supplied. This is because under the limited conditions of a bucket, the supplies stored in the soil are quickly depleted. Rock flour, which is sprinkled on the soil in the root area once a year in spring, provides a remedy here. Then it is poured vigorously. Apply 150 to 300 g per m², depending on the lime content of the soil. The more calcareous the soil, the less you should fertilize. The rock flour also has the advantage of buffering the pH of the soil for Mediterranean plants. Plants are most comfortable at a pH between 5.8 and 7.0.
How to make your own oleander fertilizer can be found here !
Fertilize oleander with blue grain
Especially for plants like the oleander, which are mostly kept in pots, you can also use the mineral fertilizer option. However, make sure that you fertilize with blue grain according to the manufacturer’s instructions and also add the necessary trace elements. Because even if overfertilization in oleander is not life-threatening, it is not good for the health or appearance of the plant. Overfertilization is indicated by brown discoloration of the leaf margins.
The damage to the plant’s fine roots caused by soil salinity remains invisible. In the event of overfertilization, flush out the tub containing your oleander with plenty of water without causing waterlogging, and do not fertilize again until the plant has recovered. Sometimes this can take a long time, as damaged leaves must first be torn off and replaced with fresh ones.
Fertilize oleander with coffee grounds
Even what is usually declared as waste can serve as a source of nutrients for the oleander. It is better to let coffee grounds or banana peels go into the soil than into the organic waste. Dried and incorporated into the planting substrate, they provide your oleander with an inexpensive and organic alternative to store-bought fertilizers. Coffee grounds, however, have an acidic effect on the soil. If it becomes too acidic for your oleander, the availability of nutrients in the soil will be limited.
Lime can help in this case. And in this case, organic waste can also become a treasure trove: Simply mix in a fertilizer made from crushed eggshells as a source of lime. If you use rock meal to provide your plants with important trace elements, you can also dare to use plant residues as a fertilizer alternative, because rock meal reduces the unpleasant odor of manure and makes it an attractive fertilizer option. In this way, you can put plant residues to a useful secondary use, just like weeds in the garden.