Grow Rock Info
 

The hydroponic guy gave me some free grow rocks to try. Does anyone have any other information for me. Does it leech anything? ginnibug

Hydroponic grow rocks are excellent for orchids that like to dry quickly. When you hear people refer to Leca (lightweight expanded clay aggregate) they are talking about products similar to yours. I use them for my cattleyas and laelias. They don't leech anything that will harm the plants. They work best in a humid environment. If your climate is very dry, you may want to mix it 50/50 with some bark or coconut husk chips to hold a little more moisture. Besides hydroponic grow rocks, orchid growers use other rock mediums like lava rock, Dyna-rok II or Staylite. They're all safe for orchids and have a neutral pH.

I'm going to try it to see if it is a good sub for the diatomite rocks that I so dearly loved and can't get anymore. I did truly love it for my catts. Only drawback from diatomite rocks are that they do finally breakdown and flake apart.I was really interested in seeing whether they leech any silica because I don't want to do like a liquid supplement or anything like that. ginnibug

I could've sworn that rePotme Orchid Supplies - Orchid Mix - Orchid Pots - Orchid Care - Orchid Fertilizer still sells diatomite...

If you need small diatomite, you can get it from NAPA & CarQuest. I'm trying it for Cypripedium, but they seem to be a little too fine grained for epiphytic orchids.

When I first found diatomite I ordered two of Maidenwell's sample collections. So I got two bags of each size that were available. Used those, except I didn't have that much use for the smallest size which is pretty close to dust. The diatomite holds moisture well and I love the added benefit of the silica ( strengthens up the leaves) but I know at some point I'll have to find an alternative. So I'm just trying to do some advance homework to see whats out there.

When I went to the hydroponics store I bought a small package of the expanded shale as well. Then the store owner gave me a couple sample bags of this "Grow Rock" stuff. He said it's recycled glass that is super heated and it doesn't normally float in the pots like the diatomite was prone to do, so that's a plus. But I was just wondering if I would get the leeching effect of the silica like I had before from the other stuff. And really I don't have that much information on the expanded shale either. I was also curious about whether either product is prone to salt build-up too, because over time I could get that with the diatomite . Thanks so much for whatever light you can shed on this for me.Ginnibug

Yippee! I found my answer!!

The product is called "Growstones" not grow rocks. I found the info on the silica uptake by the plants on the Growstones.com website, on their blog page. The one and only blog entry is about how silica is available to the plants using growstones. So maybe I have found my diatomite substitute. Lets see how well this works. I can probably use it as a top dressing on stuff that don't normally get it in the mix as well. What do you think? ginnibug

My wife has introduced growstones into our media mixes. She really likes them, and so far I agree. They're lighter than LECA products, and the round LECAs, for us anyway, roll around like marbles and don't pack well in the pot. We've been using them for a year or so now.

Steve

Be careful. Grow stones are made from foamed recycled soda-lime glass, so is basic in nature (pH=8), as opposed to the acidic environment orchids prefer, and may (I am only speculating, so don't hold me to it) expose the plants to too much sodium.

Also, don't believe all you read in marketing hype. SiO2 is extremely insoluble in water, so it is doubtful that the media components add much. If such minerals did provide it, then so would a clay flower pot or LECA, as clays are mostly silica, too.

Well I don't use it as the sole potting media.So it shouldn't affect the ph too terribly. I use it as mix additive. But I think it does help the plants a ton.

Just had some guy on the other forum tell me that plants don't need silica. And "rocks" are inert and apparently don't give off anything. That's not what my plants tell me. ginnibug