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Orchids Cultivation




Bark or Sphagnum moss, which one is better?


Part I. Introduction of the Orchids substrate

There are two types of substrates be used in the growing of Phalaenopsis, bark and Sphagnum moss. In Europe, the fir bark mixed with others substrate was selected. The sphagnum moss is very popular in Asia, especially in Taiwan, China and Japan. Which substrate is better for the growing of Phalaenopsis?

The functions of the substrate for the orchids culture are:

1.      Provide the water and nutrient

2.      Maintain the aeration of roots

3.      Served as the anchorage for the fix of roots. 

Different substrates have different characteristics. Coarse particles such as bark and coconut fibers could provide more space for the air. However, the water holding capacity is poor. Fine substrates, such as sphagnum moss and fiber peat had the good water holding ability. The disadvantage for these materials is the poor aeration function. The adequate substrate need to maintain the sufficient oxygen for roots respiration, provide the space for roots development and provide the water and nutrient continually. In other words, a good substrate could keep the balance between the water and air. Coarse particles are good at the air aeration and increase the size of cavities. Fine particles maintain more water and nutrient.

The characteristics of the Phalaenopsis roots are exist of the chloroplasts as the organs have the photosynthesis function. The national habitat of this orchids is the epiphytic plants. As the roots are exposed to the air, they could absorb the moisture from the air vapour, or the water.

Beside of the characteristics of aeration, water and nutrient holding ability, the others requirements of substrates for growing of Phalaenopsis include:

1.      It should be long-term stability, not rot or decompose within a few of month.

2.      It should not contain any toxic materials.

3.      It should have the enough space for root development.

4.      It should be able to fix the orchids.

5.      It should absorb water quickly and release it with vapour slowly.

6.      It could absorb nutrient and release it slowly.

7.      It should be supplied the mineral addition of Calcium and Magnesium. 

By the above requirement no substrate could meet all required conditions. Sphagnum moss is so popular in Asia region. The substrate is very useful for the deflasked plantlets. As the plantlets were taken out from the flask, they are very easy to be dehydrated. Sphagnum moss has the excellent water holding ability and could be the adequate substrate for these younger plants. However, the sphagnum moss made the transplanting work very difficulty. It is not easy to pull out the moss form the roots. The root was easy to damage in this moss pull operation. The other method is to surround the old moss with the fresh moss. However, the old substrates could be de composed and increase the pH value of the substrate.

The bark was not utilized directly in the Netherlands. The mixing of the substrates are the basic technique for different crops. For example, some mixture substrate was composed of 90 of the coarse parts and 10 of the finer parts. The mixing of two kinds of substrates must be uniform in the pot. Some nutrients were added into the mixture.

According the content of the Cultivation Guide Phalaenopsis – Knowledge for professionals (Anthura B. V. and Bureau IMAC Bleiswijk B. V.), there are two mixtures recommended by Anthura B. V.:

A.    Mixture 1:

10 kg Agrofoam 10mm, 25 Peat dust fraction 1, 45 Bark, 5-15, 200 liter perlite, 3 kg/m3 Dolokal ( for pH level adjustment) and 35 g/m3 microelements.

B.     Mixture 2:

30 PE flakes, 2.5 kg/m3 sphagnum, 55 fine bark, 15 medium bark, 2 kg/m3 Dolokal, 500 g/m3 PG mix (basic nutrients).

The substrates introduced by above Culture Guide include:

a.       Polyurethane or polyether clumps (PE flakes)

b.      Sphagnum: especially used at the start stage to help the good moisture distribution in the pot.

c.       Bark

d.      Peat

e.       Coconut husk

f.       Perlite


About the author:

Professor Chiachung Chen, Ph. D.

Biosystems Engineering Laboratory
National ChungHsing University

250 KuoKuang Rd.,

Taichung, Taiwan 40227

Tel: 886-4-22857562, Fax: 886-4-22857135

Web site: http://bse.nchu.edu.tw

Email: ccchen@dragon.nchu.edu.tw