Orchid Care OrchidTalk Orchid Forum Links Nursery

Welcome to OrchidTalk Orchid Forums

The Friendliest Orchid Community on the Internet!

  •  » Learn to Repot your Orchids
  •  » Learn Orchid Care Tips and Secrets
  •  » Find the perfect Orchid for your Growing Environment
  •  » Chat with Orchid Growing Professionals

OrchidTalk - "Bringing People Together to Grow Orchids Better!"

Let us help you grow your Orchids better; Join our community today.

YES! I want to register an account for free right now!

Register or Login now to remove this advertisement.

Results 1 to 3 of 3

Thread: Rock Wool Medium

Click here to increase the font size Click here to reduce the font size
  1. #1
    Real Name
    Ray Barkalow
    My Grow Area
    Join Date
    Oct 2012
    Oak Island NC

    Default Rock Wool Medium

    Over at another forum, there are folks that use Grodan rock wool cubes for their phrags, so I thought I'd get some to experiment with.

    Grodan is a long time manufacturer of inorganic rock wool horticultural media. This product is manufactured by melting basalt and spinning it into fibers, much as insulating fiberglass is made. The fibers are produced as a mat, then cut into smaller pieces for use. In this case, they're approximately 1 cm cubes. The fiber is approximately 50/50 hydrophilic/hydrophobic, so is supposed to remain fairly airy.

    I did a little experimenting:

    • I filled a container (roughly equivalent to a 6″ pot 6″ tall) with the dry cubes – they weighed only 2.25g.
    • They were soaked in RO water for 36 hours
    • Saturated, they weighed 308g. After 5 days of sitting open in warm, humid air, only 15% of the water had evaporated.
    • The saturated cubes occupied approximately 55% of the container volume, leaving 45% air space.
    • The pH of the soak water was 5.4, so should be fine right out of the box.
    • The EC was only 20 µS (for reference, a 100 ppm N solution of K-Lite has an EC of 710 µS).

    I am planning to experiment with my phals in a mix of LECA and cubes (75/25? 50/50?). I currently grow them in straight sphagnum, because the evaporative cooling in S/H pots in my home in winter cools them too much.

    I can conceive - based upon the water retention - that a blend will serve to "flatten" the moisture gradient in an S/H pot, keeping it moist to the top.

    If anyone else wishes to play with it, I have a few boxes available, so feel free to PM or email me.

  2. #2
    Real Name
    Bruce Brown
    My Grow Area
    Favorite Orchid(s)
    Cattleyas & Slippers
    Join Date
    Mar 2003
    Member's Country Flag


    We tried this stuff and with our watering schedule, everything stayed too wet. I'm really happy using coconut husk to hold moisture as part of my potting mix.


  3. #3
    Real Name
    Ray Barkalow
    My Grow Area
    Join Date
    Oct 2012
    Oak Island NC


    My experience in the old days was the same, but I think mixing it as a minor additive to something like LECA has merit.

Similar Threads

  1. Lava Rock & Sponge Rock
    By chrisa in forum General Orchid Culture
    Replies: 6
    Last Post: January 12th, 2013, 07:27 PM
  2. UPDATE :: 7 Months period after repotting Phals into perlite and lava rock medium.
    By empiref in forum Semi Hydro / Lights / Greenhouses / Accessories
    Replies: 18
    Last Post: January 10th, 2011, 12:08 PM
  3. Finally got around to planting that rock pot
    By pavel in forum Eye Candy
    Replies: 11
    Last Post: August 27th, 2009, 10:30 PM
  4. Little Rock, Arkansas Zoo...
    By Brutal_Dreamer in forum The Jungle
    Replies: 13
    Last Post: July 24th, 2006, 09:51 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
OrchidTalk --An Orchid Growers Discussion Forum brought to you by River Valley Orchidworks. A World Community where orchid beginners and experts talk about orchids and share tips on their care, cultivation, and propagation.