VERSAROCK® AS A POTTING MEDIUM FOR ORCHIDS
by Wendy Witnish
I would like to tell you about my experience with Versarock®, a product widely used in hydroponic horticulture. It is a naturally occurring 'premixed' ceramic that has a highly porous structure that won't aggregate when wet. The granules typically have 4, 5 or 6 faces that provide pore spaces between granules, allowing good aeration and infiltration.
Versarock® interested me because its properties indicated that its use might take some of the hard work out of repotting and could perhaps eliminate repotting altogether, simply allowing me to keep potting on as my orchids grew. I began trialling three plants in January, 1996. Two months later these plants were doing quite well and I took the 'quantum leap' and repotted my entire collection of Australian natives and mixed genera into Versarock®.
I decided I would use all Versarock® or no Versarock®. Some growers mix it with their other potting materials to provide better aeration but in my case it would have defeated the purpose. If I mixed it with bark, I would have not been able to pot on, as old bark would first have to be removed. Versarock® is recyclable and can be sterilised but this would be difficult in the case of a Versarock®/bark mixture. Because Versarock® does not break down, I reasoned that it should be possible to pot small plants into large pots. This was a mistake because over-potting the plants did not establish a good root system. After repotting the orchids in smaller pots, they resumed growth very well. I've also found that my new 'mix' simplifies feeding with slow-release fertiliser - just tip off the top layer, add fertiliser and top up with Versarock®. It absorbs water very rapidly, so I hope that any tendency for root burn will be eliminated.
Versarock® is clean to use; it contains no fines apart from a little powder that washes through on watering. It has a tendency to turn green on top but this is not a problem as it's a simple matter to replace the topmost layer with fresh Versarock®, giving the pot a fresh, clean appearance. There also seems to be no build-up of salts from continued fertiliser use. I've heard some growers say that slaters don't attack orchid roots but they and worms had a field day with some of my orchids, especially Sarcochilus, when they were potted in bark. Since potting in Versarock®, the problem has disappeared. I also hoped that it would deter snails but it hasn't! Most glasshouses have a mouldy smell, which I dislike. Versarock® has eliminated the mouldy smell and its use could therefore be an asset to those growers who are allergic to mould. Perhaps watering can be carried out less frequently when orchids are potted in Versarock® but I still water my plants as often as I did when using bark. If plants should dry out, they rewet very rapidly in Versarock®.
With the exception of cymbidiums, which don't grow well for me, I've had real success with Versarock®. I've grown a plant of Encyclia cochleata since 1990 but it had never developed a good root system until I repotted it in Versarock®; now it is well established and flowers for months on end. Another success story is Stelis porschiana, which has flourished since I transferred it to Versarock®. Previously, it kept falling out of its pot because its roots were so poor. My pride and joy, Howeara Mini Primi, a past winner at an OSCOV show, is thriving and covered in spikes again this year. Laelias love Versarock®, as do oncidiums (including the equitant types), laeliocattleyas, sarcochilus and dendrobiums; even my cool growing paphiopedilums are doing well.
Versarock® is available from several sources, including Duralite Pry. Ltd., 54 Old Dandenong Road, Heatherton (tel. 9551 6756). There are two grades, fine and coarse; I prefer the latter.