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Orchid culture - theory and practice part 2


Following on from part 1 of the article's conclusion that the planting matter needs to be flushed regularly when using salt fertilizer, I will present some new insights as part of this post. This raises the question of how effective such flushing with rainwater etc. actually is.

To answer this question, I used two orchids from my greenhouse, each in a 10 cm clay pot, for the following tests. The salt content of the substrate in one pot was determined as a starting value with the "shaking method" described in the previous article with 580 µS.

Three times a day at intervals of about three hours, 500 ml of rainwater (35 µS) was slowly poured through the second pot and collected again under the pot.

This process was repeated for five consecutive days. The collected water showed the following salinity:

A “total” of 2761 µS was washed out in 15 rinsing processes. The substrate then had a salt content of 180 µS. It is obviously not possible to simply add up the measured values for the flushing water.

However, this result shows that occasional rinsing of the substrate cannot prevent an increasing salt content in the substrate.

During a visit to the Holm nursery in Bedburg-Hau (Germany), owner Marco Holm reported that a large number of his orchids are sprayed or watered three times a week without fertilizer and only then do they receive their fertilizer ration. This increased effort is made to allow accumulated salts in the plant matter to dissolve and flush out. A single rinse is obviously not enough - the accumulated salts are dissolved, but not rinsed out.

In my last article, I had set the goal of only watering my orchid cultures with rainwater over the substrate at least during winter.

During this time I have been intensively researching alternatives to nutrient salts as fertilizer. I quickly came across organic fertilizers that can be of animal or plant origin.

However, these fertilizers do not have an immediate fertilizing effect and must first be converted by microorganisms (MO) in the substrate. This means that fertilization in line with growth is almost impossible and can also have negative consequences such as rot in the substrate.

When researching the Internet, I came across the interesting topic of compost tea.

Now, conceptually, one might think that compost is doused with hot water and then, after it has cooled and filtered, spread over plants.

However, the hot water would kill the MO and its waste products, the important enzymes and other growth-promoting substances in the compost.

For this reason, organic farming has developed the so-called bucket method in order to let the MO work for you in the field, which is so necessary from your point of view:

Approx. 500 ml of compost is poured into a sufficiently large bucket with rainwater and air is fed into this mixture using an aquarium pump. In addition, the mixture is stirred several times. By adding air, an extraction process is accelerated and the whole thing cannot turn into putrefaction.

Only fully processed compost (mature compost) should be used as starting material. However, since it was the middle of winter, I could not find this compost anywhere.

But the Internet also offers a solution for this: earthworm humus

Earthworms play an outstanding role in the formation of humus in the soil and thus make a decisive contribution to the development of soil fertility. They eat dead organic matter from plant debris and animal waste. During the digestive process, organic and mineral components are mixed, concentrated, and excreted as nutrient-rich feces.


Nutrients from the worm humus are immediately available to the plant and provide plant-supporting components as well as valuable MO in their natural composition and variety. Worm castings also activate soil biology, stimulate growth and prevent a wide range of soil and leaf-borne plant diseases. At this point it would go too far to list the further benefits of treating plants with worm castings. I can only refer anyone who is interested in this topic to the scientific findings on the homepage - everyone can evaluate the advertising character of the product on offer for themselves.

The benefits of worm humus extract convinced me and were worth trying once.

Worm castings were quickly obtained and initially 500 ml of worm castings per 15 liters of rainwater were treated with air. This extract was then filtered, poured into the pouring tank and made up to 100 liters with rainwater. The "salinity" of this fertilizer solution is around 130 µS and the orchids were watered over the substrate with a shower over the next ten months. An average nutrient analysis from my worm humus supplier results in the following values with the dosage mentioned here:

130 mg nitrogen, 20 mg phosphorus, 21 mg potassium, 12 mg magnesium and not inconsiderable amounts of trace elements.


In addition, the plants were sprayed with a foliar fertilizer consisting of a salt fertilizer and the chlorophyll juice already described in the previous article. The salt content of this foliar fertilizer was a maximum of 600 µS (rather half in the winter months).

The growth of the orchids and their roots was remarkably good during this time and the flower yield was also good. However, a large part of my paphiopedils did not show satisfactory growth. The high salt concentration of the previous years had severely affected the rooting of these plants. Most of these plants recover only hesitantly.

Because of the suboptimal rooting of the paphiopedils, I also gave some thought to the calcium supply of orchids. It is known that when using bark substrates, a basic lime of at least five grams of carbonate of lime is added to the planting material per liter. This gives the orchids the calcium they need for growth and at the same time the always acidic bark substrate is buffered a little towards a neutral pH value. In the course of the culture period, the pH value of the bark substrate also falls into the acidic range, a Maintenance liming would therefore be helpful to at least partially stop the acidification of the substrate.

For this reason I add 15-25 grams of carbonate of lime, bentonite, etc. to 100 liters of rainwater, set the pH to around 6.0 and then water my orchids with this water every two to four weeks.

Alternatively, you can also "blend" your rainwater with 10 - 15% tap water for this purpose. In most cases, tap water contains a sufficiently high proportion of calcium and has a pH value in the neutral range.



Another important topic in orchid culture was and is the correct handling of pests and diseases of orchids. A few years ago, the Federal Office for Consumer Protection and Food Safety carried out a reassessment of the approval of plant protection products, especially in the allotment garden sector or in private plant breeding.

Well-known and effective means are no longer available for orchid culture and we have to look for alternatives.

In organic gardening, a new product is being advertised as a kind of miracle cure: neem oil, also known as neem oil. The purely ecological agent, which is obtained from the seeds of the Indian neem tree, is effective against a wide variety of pests such as beetles, caterpillars, lice or spider mites as well as against snails and fungal infestation. If you spray the neem oil directly on the leaves, it helps against acute pest infestation. If you add it to the irrigation water, it strengthens the plant from the inside out via the roots. The great advantage of neem is that no resistance develops in the various pests. Beneficial insects such as ladybugs and bees are not endangered by neem.

This is due to the active ingredient azadirachtin contained in neem, which does not kill the pests immediately. However, it causes a loss of appetite and the willingness to reproduce is greatly reduced. This active ingredient is broken down in the plant after three weeks. Neem products should therefore be used as a precaution at intervals of two to four weeks!

I sprayed only neem oil in the prescribed dosage over my orchids for several months. I could hardly find any pests during this time. However, paphiopediles that emerge from the base of the new leaves have had some flower shoots stuck. It is known that oils can clog the stomata of plants. The flowering shoots of my orchids have probably also been damaged.

Because I was still very satisfied with the results overall, I wanted to continue experimenting with neem myself and came across neempress cake.

The neem press cake is a "waste product" (press residue) in the production of neem oil and still contains sufficient amounts of the active ingredient azadirachtin. For this reason, it is also used in organic farming against various pests.

To produce a pesticide, I put 150 g of neempress cake in ten liters of rainwater and treat it with air (as described above). After a day or two, I filter this extract through a fine-meshed sieve or through an aquarium net, dilute the extract again with rainwater in a ratio of 1:1 and spray the orchids with it immediately.

A pest infestation has hardly been detectable in the last few months through the use of this neem extract - however, as a precaution I spray my orchids with this extract over the leaves every two to three weeks. Incidentally, the extract from neempress cake also has a fertilizing effect.



I will continue to monitor the results of my experiments in the coming months and then publish them here in Part 3.


An extra article has now been published on the subject of neem:




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