Fertilizing Bonsai: Professional Tips & the Right Fertilizer

67 / 100

Even the smallest tree needs nutrients every now and then. We show when and how to fertilize your bonsai and which fertilizer is best suited for this.

Fertilizing bonsai: professional tips on the procedure & the right fertilizer

Bonsais need a special fertilization that is adapted to the long-term pot culture [Photo: wonderisland / Shutterstock.com]

Just like with its free-growing conspecifics, the care of a bonsai includes the regular supply of nutrients. The right fertilization does not only depend on the type of plant that was raised to be a bonsai. The location, the season and the weather conditions are also reflected in the nutrient requirements. In addition, the culture in high-quality bonsai soil has a few special features. This must also be taken into account when choosing the fertilizer, the amount of fertilizer and the time of fertilization.

Since the bonsai has to make do with a relatively small volume of soil, its care requires particularly careful and well-dosed fertilization. But caution is not only required because of the limited root space: Since very different tree species can be trained to become bonsai, there is no universal bonsai fertilizer. In the following article, however, we would like to introduce you to the general principles of bonsai fertilization.

When should you fertilize bonsai?

Basically, first of all, your bonsai should be fertilized each time it is transplanted. The repotting takes place in early spring and the old substrate is removed from the roots of the bonsai as completely as possible and the roots of the tree are slightly shortened. The selected bonsai soil is then fertilized with 20 grams of horn shavings per square meter. So there is just one teaspoon on a small bonsai bowl. The horn shavings provide nitrogen and phosphate for a long time and thus serve as basic fertilization.
After planting, you should not fertilize for four weeks. The horn shavings do not release any nutrients in this short period of time – and that is a good thing, because the lack of nutrients stimulates the formation of roots in the bonsai.
Then regular fertilization begins, the interval between which depends on the choice of fertilizer. The fertilization takes place from budding in spring to autumn and is paused in winter. After all, in the cold season of the year, our photosynthetic gardeners run on the back burner and quickly react negatively to too much fertilizer.

Fertilizing bonsai: professional tips on the procedure & the right fertilizer

In contrast to indoor bonsai, outdoor bonsai are not fertilized in winter [Photo: ahau1969 / Shutterstock.com]

In the case of evergreen indoor bonsai, which are not so strongly exposed to the course of the seasons, the reduction in nutrient requirements is also kept within limits. This means that with indoor bonsai you have to provide energy with regular fertilizers even in winter. However, fertilization and watering of the bonsai are reduced in winter. If a plant is ailing, you should first rule out whether over-fertilization might be the reason. The nutrient supply is initially stopped in order to wait for any improvement. If you have ruled out over-fertilization, you can start fertilizing again. If over-fertilization is the problem, the bonsai can even shed its leaves early. You can find out what other reasons for the shedding of the leaves on a bonsai tree can be found here.

Summary: when to fertilize the bonsai?

  • Plant fertilization: 20 g / m² horn shavings, then stop fertilizing for 4 weeks
  • Garden bonsai: spring to autumn; do not fertilize in winter
  • Indoor bonsai: spring to summer; reduced in winter
  • Diseased plants are not fertilized

Bonsai: how and how much fertilize?

Since bonsai is not a fixed type of plant, but a multitude of beautiful plants that fall under the collective term “bonsai” due to the way they are cultivated, the question of the amount of fertilizer is difficult to generalize. The following factors influence how much you should fertilize:

  1. Fast growing bonsai need more fertilizer than slow growing ones.
  2. In the summer half of the year, more fertilization is used than in the rest phases in the winter half of the year.
  3. If substance is to be built up, more fertilization is used than if only the shape is preserved.
  4. In stressful situations such as heat stress, illness or after repotting, there is little or no fertilization.
  5. The older the tree, the lower the need for fertilizer, as older plants grow much more slowly than young bonsai.
  6. If the bonsai is to bloom or is already doing so, you should only fertilize a little, otherwise the bonsai could shed its flowers.
  7. Bonsais with a lot of undergrowth are fertilized more heavily.
  8. Permeable substrates with a low organic content are fertilized more often and in small doses. Bonsai soils with a higher organic content can be supplied with fertilizer at longer intervals.
  9. Species in need of nutrients are fertilized more than frugal species.

However, one golden rule applies to every bonsai: It is better to fertilize at regular intervals with small doses, otherwise over-fertilization will quickly occur. Your bonsai reacts to this by shedding leaves or, in the worst case, even dies. So that the plant can recover from over-fertilization, you should wash the excess nutrients from the substrate or repot the bonsai in new bonsai soil. So that over-fertilization does not occur in the first place, it is important to adhere to the instructions for use of the fertilizer when fertilizing.

Fertilizing bonsai: professional tips on the procedure & the right fertilizer

When a bonsai starts to flower, the fertilization should be reduced or stopped [Photo: cowardlion / Shutterstock.com]

Summary: How (much) should you fertilize your bonsai?

  • The amount of fertilizer depends on the growth, growth conditions, age and state of health of the bonsai as well as the type of plant and the type and vegetation of the bonsai soil.
  • Bonsai soils with a slightly higher organic content are fertilized at slightly larger intervals.
  • The golden rule for fertilizing bonsai: fertilize in small doses at regular intervals.
  • If there are signs of over-fertilization, rinse the substrate or repot in fresh, high-quality bonsai soil.

The perfect bonsai fertilizer

Of course there are special bonsai fertilizers. However, these probably differ from other fertilizers mainly because of their higher price, because bonsais also need the same 14 essential nutrient elements as other plants. Certainly there are species-specific differences, but of course no universal bonsai fertilizer can meet them either.

Fertilize bonsai organically or minerally?

Basically, fertilization in spring should be nitrogen-stressed in order to stimulate leaf growth. In summer, a balanced fertilization is important and in late summer and autumn a good supply of potassium is crucial, especially for garden bonsai, in order to ensure the necessary frost resistance.
Then there is still the choice between organic and mineral as well as liquid and solid fertilizer. This choice is up to you and of course bonsai experts have likes and dislikes too. However, both are possible. Organic as well as mineral liquid fertilizers are added to the irrigation water, have to be applied at the shortest possible intervals and are available very quickly. Solid mineral fertilizers are quickly available, but have an unnecessarily large ecological footprint and can quickly lead to over-fertilization if incorrectly dosed. Solid organic fertilizers work a little slower, but longer and do not trigger over-fertilization.
The special organic fertilizer pellets can be dissolved in the irrigation water or attached to the surface of the substrate in fertilizer baskets – the small baskets prevent them from floating away, being blown away and being consumed by birds.

Our Plantura organic universal fertilizer can also be used to fertilize bonsai in summer. The Plantura organic lawn fertilizer is also perfect for the stimulating start fertilization in spring. For the autumn fertilization of garden bonsai we recommend our potassium-accentuated Plantura organic autumn lawn fertilizer. Thus, the set for an animal-free and natural supply of nutrients to your bonsai is already complete and the dosage only needs to be adjusted as described above.

Tip: As a bonsai, the winter linden should only be fertilized organically, as the roots are extremely sensitive to salts.

However, natural organic fertilizers such as compost and manure are not suitable as fertilizers for your bonsai. They have to be worked into the top layer of the earth every year – this turns out to be extremely difficult with the shell culture.

Bonsais, which like the azalea ( rhododendron ) or the fucient tea ( Carmona microphylla ) are sometimes known for their beautiful flowers, need a fertilizer with a high phosphate and potassium content, because this contributes significantly to the development of a lush flower coat. And evergreen conifers enjoy an extra amount of magnesium so that their needles remain bright green even in winter.

Fertilizing bonsai: professional tips on the procedure & the right fertilizer

Potassium and phosphate promote the formation of flowers in the azalea or the fucient tea [Photo: Huy Thoai / Shutterstock.com]

Summary: The perfect bonsai fertilizer

  • It doesn’t necessarily have to be the special bonsai fertilizer
  • Organic, mineral, liquid or solid fertilizers are possible
  • Fertilizer pellets are attached to the surface of the substrate with a basket
  • The right fertilizer composition generally depends on the time of year
  • Bonsai in bloom need more potassium and phosphate
  • Evergreen conifers benefit from a little extra magnesium

The perfect bonsai fertilizer for every season

As mentioned above, the fertilization can be adapted to the growth of the bonsai. A distinction is made between outdoor bonsai and indoor bonsai. When budding in spring, bonsais need a nitrogen-rich fertilizer – whether indoors or outdoors. In this way you support the formation of leaves, shoots and buds. Deciduous trees, which have to regenerate their leaves, need more nitrogen here than conifers. In summer, a balanced NPK ratio is used, although young and fast-growing bonsais require a higher proportion of nitrogen than old and slow-growing plants. In autumn, indoor bonsais continue to be fertilized as before, because the plants in the house are largely exposed to constant temperatures and balanced lighting. In the case of outdoor bonsai, continued nitrogen-based fertilization would not be beneficial. Instead of promoting the shoot formation with nitrogen, you should use a potassium fertilizer for autumn fertilization in August and September. This means that shoots that have already formed harden faster and the resistance of the plant to frosty temperatures is increased. Use Patentkali for this, for example. This not only contains potassium, but also magnesium, which is important for chlorophyll formation. Those who swear by mineral fertilizers like patent potash on organic autumn fertilization with phosphorus, potash and magnesium can at the same time support growth and flower formation in spring. In winter, garden bonsais are then no longer fertilized at all and indoor bonsai are only fertilized to a limited extent.

Many thanks to Floragard for the support!

* in cooperation with Floragard

Fertilizing bonsai: professional tips on the procedure & the right fertilizer

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *