Fern fibre culture of orchids is not new. A lot of tree ferns have been harvested for this purpose over the years, particularly in South American and Asian countries. In some cases harvesting of some vulnerable species has finally resulted in them being protected from further harvesting. This is not the case in New Zealand.
The main species being harvested is Dicksonia fibrosa. Being native fauna it is protected and may only be harvested with the approval of the Ministry of Primary Industries (MPI) from privately owned land under a careful permitting regime. Fernwood have secured rights to harvest from large tracts of uneconomic farmlands that are reverting back to forest. They selectively log (approximately 1 in 5 tree ferns).
To obtain permits they submit a plan to MPI, who inspects the area to be harvested. Upon receipt of the permit the selected ferns are harvested and extracted by helicopter. Upon completion, MPI inspects the harvested area. The point that I am making is that harvesting is conducted responsibly and is sustainable and ethical, and is overseen by a government agency.
Let us consider the basic requirements for growing paphiopedilums. In New Zealand they require shelter, preferably enclosed (e.g., glasshouse). Heating and ventilation is advisable that will allow winter minimum temperatures of 10 degrees, and a maximum summer temperature of 30 degrees Celsius. Shading of about 30% in winter, and 70% in summer is advisable. Paphiopedilums like water, but it is easy to destroy roots if they remain wet, particularly during cool nights in winter.
When considering if you should water, if in doubt during summer do water. If not sure during winter, withhold watering. Following watering it is recommended that a balanced fertilizer at half strength (CF 5) should be applied over the leaves so that it percolates down through the pot. Watering should be done as early in the morning as is practical when you are expecting a bright sunny day to follow so that the leaves and axils are well dry before the coolness of night.
When using bark, re-potting annually is recommended. Plants should be removed from the old pot, dead and unhealthy roots should be removed. Use a clean sterile pot just large enough to accommodate the roots and water the plant in. While this is a description for paphiopedilum culture, many genera have similar requirements.
Please note that for the remainder of this article any reference to fern fibre, or fibre, refers exclusively to Dicksonia fibrosa.
About three years ago I conducted some trials for Fernwood. I used complex paphiopedilum seedlings of the same grex that were ex-flask for one year, planted in bark, and not growing well. I selected seedlings that were of approximately the same size and divided them into three groups. Equal numbers were re-potted into tubes of fibre, a mixture of fibre and bark, and bark alone.
Evaluation after a year yielded very clear results. The plants in fibre alone were well ahead of the other two groups. Those in bark + fibre were ahead of those that were planted in bark alone. It is clear to me that mixing fibre and bark is a significant mistake and that fibre is quite superior to bark.
Just over 4 years ago I planted several flowering sized complex paphiopedilums in fibre as an experiment. These plants have not been re-potted or potted on. The fibre remains in excellent condition, and the roots are very healthy. Because of this experience all of my paphiopedilums are potted in pure fibre. They are not only re-potted annually, they are not re-potted at all unless they plant is growing poorly.
As they outgrow the pot, I pot them on. In other words, the root ball remains intact and is inserted into a slightly larger pot after plucking out dead roots. Fresh fibre is eased in to fill between the side of the pot and the root ball. The fibre is never pressed in hard. It is tamped in just tightly enough so that it has a springy feel when pressed. Since growing my plants in pure fibre I have enjoyed better growth and flowering, and the work required in the greenhouse is significantly reduced.
There are two other things that differ when potting in fibre. Firstly, slightly less frequent watering is required. Fibre hold a lot of moisture (and a lot of air) so take care not to over water. Secondly, I find that a more dilute fertilizer is appropriate. I use 30% strength rather than the 50% that is usually used with bark.
Let’s look at the characteristics that make fibre superior to bark as a potting substrate for orchids.
- Slow decomposition. Alan Ford (Fernwood) found a felled intact fibrosa log covered in pine needles in a pine forest. He knows that this log has been there for at least 50 years, because the forest is in its second rotation. I encouraged him to take a sample for pH analysis. It measured the same as freshly harvested product, meaning that there was insignificant decomposition.
Advantage: No repotting, infrequent potting on. Labour saving.
- Fibres are very hairy, providing a very high surface area in contact with orchid roots.
Advantage: High surface area allows more efficient nutrient absorption by the roots. Excellent water retention (less frequent watering). even moisture throughout the pot due to capillary action.
- Growth friendly pH of 5.5 – 5.8. This varies little over time because of fibres resistance to decomposition.
Advantage: Healthier plants, more and better flowers. Less maintenance work
- Excellent re-wettability.
Advantage: If allowed to over-dry, watering re-wets the medium well.
- Dilute Fertilizing. When using bark, much of the nitrogen in a fertilizer is used by the bacteria that decompose the bark. Because fibre is so slow to decompose, little of the nitrogen is lost.
Advantage: Cost saving, and less fertilizer build-up.
- Stable root ball. A plant may be removed from a pot with little or no substrate spillage, unlike bark.
Advantage: Easy inspection of root health and judging of watering, and potting on.
At this point I should briefly discuss fertilisers. Because growth trials that I conducted were aimed at informing the American market I decided to use a fertilizer that they would be familiar with. I chose Dyna Gro, using their “Grow” fertilizer and Pro TeKt, each at a rate of 2ml/5 litres of water, achieving a CF of 3.
The advantage of this product is that the manufacturers have managed to develop a way of including all of the major and micro nutrients in proportions that plants require. This is difficult to achieve. The choice of Dyna Gro was a happy “accident” because I now find that most plants that I have grown for years but yielded few flowers are now flowering well. Reading has since shown me that some micro nutrients are essential for good flowering. The choice of fertilizer is very important!
There is a rapidly increasing interest in the use of fibre. I am aware that growers are getting excellent results growing phalaenopsis, dendrobiums, oncidiums, miltonia, miltoniopsis, and bulbophyllums in this medium. Other genera will also benefit, while others may not. I have heard of both good and indifferent results for cattleyas, for example. If you haven’t yet tried it I would encourage you to do so. Proceed with excitement and anticipation blended with caution. Monitor and assess your watering in particular and do not over-pot.
Lastly, it must be acknowledged that fibre costs more than bark on a volumetric basis. Changing from bark to fibre will cost you more than a re-pot using bark. Don’t let this fool you into staying with the status quo. If you change to fibre and use my system of potting on rather than re-potting your costs over time will be less than when you used bark. Your plants and flowers will be better, and you will be inputting less work to achieve this. It is a win-win all the way so long as you balance well all the factors that your orchids require.
Better results for less!