The botanical name of the oleander is Nerium oleander. In the system, it is the only species of the genus Oleander, it belongs to the family of the dog-poison plants. The oleander grows and blooms in the poor soils of the Mediterranean countries. In German pots he is dependent on a balanced fertilization. This is the only way for the rose laurel to overwinter undamaged and to delight gardeners with lush, colorful flowers in summer. The right composition of nutrients, the amount and timing of fertilization are crucial.
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time
The oleander is not hardy. As soon as it gets frosty, he needs suitable winter quarters. For him, too, the rule applies that the darker he hibernates, the cooler the temperatures have to be. In winter it is only watered sparingly and no longer fertilized at all. In spring, when the daytime temperatures are stable at 15 ° C, it can be put outside again. You can start fertilizing after just a few days, when the leaves look healthy and deep green.
The rose laurel needs fertilization during the entire growing season from March, April to the end of August at the latest. Even if it is still outside afterwards, it must no longer be fertilized. This is the only way for the shoots to mature or lignify in time for the winter.
How often you have to fertilize the Nerium oleander during the growth phase depends on which agent is used, a slow release fertilizer (mostly organic) or a mineral oleander fertilizer.
Tip: With the last fertilization in August, an additional portion of potash fertilizer (fertilizer lime) helps with the ripening of the shoots. When fertilizing for the first time in spring, an additional portion of potash fertilizer is a good start-up aid, especially if you are otherwise working with organic long-term fertilizers.
Types of fertilizer
The rose laurel gets along very well with both types of fertilizer, with short-term fertilizers (mineral) and also with long-term fertilizers (organic or organic-mineral). If the plant shows a lack of nutrients, it is advisable to provide some kind of first aid quickly with a mineral fertilizer mixture.
Slow release fertilizer
Organic fertilizers such as compost, bird droppings, stable manure or horn shavings release their nutrients over a long period of time. They first have to be opened up by the microbacteria in the soil. There are also various long-term fertilizers to buy in stores, which, depending on the information, cover the nutrient requirements for three, four or even six months.
Mostly it is a special oleander fertilizer with organic and mineral components. So if you do not want to or cannot keep up short intervals when fertilizing, it is best to use these types of fertilizer. In addition, there is no risk of over-fertilization.
Tip: An occasional serving of coffee grounds is a welcome and natural addition to the nutrients for the rose laurel. In autumn and spring, ground eggshells give him strength for the respective changeover.
Mineral fertilizer
There is a large selection of mineral, mostly liquid fertilizers on the market. Some are tailored to the needs of flowering plants. Special oleander fertilizers are also available. They are usually added to the irrigation water once or twice a week. In this liquid form, the nutrients can be quickly absorbed by the roots.
Another type of mineral fertilizer is blue grain. It is available in liquid and granular form. These concentrates must always be diluted with water according to the instructions on the package. Blue grain consists of the macronutrients nitrogen, phosphate and potassium. The amount of the respective shares varies depending on the manufacturer. In addition, some mixtures also contain magnesium and sulfur. Common combinations are then indicated on the package as 14 + 7 + 17 + 2 (NPK + Mg) or 21 + 5 + 10 + (3 + 6) (NPK + Mg + S).
It is relatively difficult for hobby gardeners to dose them correctly, especially for container plants. In addition, there is usually a lack of micronutrients and trace elements. Too much of these salts can damage the small roots very quickly. The risk of over-fertilization is therefore rather high.
Advantages and disadvantages of the types of fertilizer
Minerals
- quick effect
- known composition
- Risk of over-fertilization
- energy-intensive production
- Liquid fertilizer is quite expensive
Organic fertilizer
- slow action but long lasting
- almost no risk of over-fertilization
- Fertilizers must be mixed thoroughly into the entire substrate
Nutritional deficiency
Anyone who works exclusively with organic fertilizers should keep an eye out for the typical signs of nutrient deficiency:
- failure to flower
- few flowers (enough sunlight?)
- small, puny flowers
- yellow leaves (many in a short time, otherwise normal aging)
Overfertilization
Incorrectly dosed liquid fertilizers and mineral fertilizers such as blue grain can easily lead to an excessive supply of nutrients, especially nitrogen. Common signs:
- many green, shooting shoots, hardly any flowers
- brown leaf margins (roots contaminated by salts)
- unsightly, dry leaf margins (visible for a long time)
If you have found over-fertilization, you can prevent further damage by a thorough watering. To do this, you pour the bucket with plenty of water and repeatedly remove the water that has accumulated in the coaster. Then stop fertilizing for a while until the Nerium oleander has recovered.
dosage
So that there is neither an overfertilization nor a deficiency, the dosage instructions for the ready-to-use fertilizers must be strictly adhered to, with liquid fertilizers as with mineral fertilizers. These fertilizers cannot be used to fertilize “in advance”. Better to use something more economical than indicated.
nutrient
Basically, the Nerium oleander needs macronutrients and micronutrients, also called trace elements. The right proportions are particularly important when it comes to macronutrients.
The macronutrients make up the largest proportion of the nutrients required by plants. They are again divided into
- primary nutrients (basic nutrients): nitrogen (N), phosphorus (P) and potassium (K)
- secondary nutrients: magnesium (Mg), sulfur (S) and calcium (Ca)
The basic nutrients are listed on the packaging as NPK information according to their proportions. For the rose laurel, for example, a mixture of NPK 15 + 10 + 15 is suitable. As a strong poacher, the oleander bush in the bucket definitely needs enough of these basic nutrients. But the secondary nutrients, which are normally sufficiently available in the garden soil, are quickly used up in the bucket.
nitrogen
Nitrogen is generally required for rose laurel growth. Nitrogen makes the shoots sprout and the leaves look healthy and green. This is how you can tell if there is a lack of poor growth and yellow leaves. Too much is usually at the expense of the flower, the plant “shoots into the herb”. The stems are long and weak.
Phosphor
Phosphorus causes the flowers to spear and supports the formation of roots. It is important for your health and above all for a healthy winter time. Too much is usually noticeable through bluish-purple, gray discoloration of the leaves.
Potassium
Potassium strengthens the oleander’s immune system. It stimulates the plant metabolism and reduces susceptibility to diseases and pests. If there is a deficiency, the edges and tips of the leaves look like they are burnt. The flowers are inhibited in their development.
Trace elements
The trace elements are only needed in small amounts, but they are essential for the health and growth of the oleander:
- Mangan (Mn)
- Chlorid (Cl)
- Kupfer (Cu)
- Iron (Fe)
- Bor (bo)
- Zinc (Zn)
- Molybdenum (Mo)
selection
Finished organic-mineral NPK fertilizers in the form of small spheres are safest and most convenient. They have the required proportions of macronutrients and also all the necessary trace elements. The granulate is worked into the soil once at the beginning of the growth phase and works for three to six months, depending on the variety and the manufacturer’s instructions. Here are some examples of “all-round carefree” fertilizer mixes for oleanders
- Compo Basacote Plus 12M (slow release fertilizer, granules, coated round grain)
- Compo Mediterranean plant fertilizer (liquid)
- Oleander fertilizer liquid HIGHTECH NPK full fertilizer for Nerium Oleander, GREEN24
- Dehner oleander and Mediterranean fertilizer, NPK liquid fertilizer
Conclusion
Regardless of which fertilization you choose, the fact is that the oleander in the tub needs additional nutrients. Repot once a year with new substrate, that is not enough to be able to enjoy lush flowering in summer. Modern combination fertilizers, specially tailored to the nutrient needs of the oleander, make it particularly easy.