Sand anybody?

[Rick]

I was reading John Doherty's article on P. sanderianum (and hybrids) in Orchids.

A lot of his culture overlaps mine for multis, but I was intrigued about his use of sand as a biannual top dress (with oyster shell).

I have sand in some bark mixes with some of my barbata types (using Lance Birk's "pretty good" mix) and have had some individual plants do very nice in it.

I know a couple of growers in my local society will mill their bark with sand, which seems to make the bark last a lot longer and drains better.

Some of the "soils" that some of the barbata are found in often have sand listed in the description.

Normally I think of sand as something totally inert, and just a drainage aid, but do you think it could be a source of silicates?

I use Protect on a fairly regular basis, which is potash, but with a good source soluble silicates.

Any opinions?

 

[Ernie]

Rick, we've been adding sand to our bark mixes, particularly for slippers, for the last several years too. Probably read it somewhere and decided it wouldn't hurt. Since, we've noticed root hairs like to grab onto it... or does the sand just stick in the hairs. Who knows. I've also read many conflicting accounts of various "silicious" media contributing Si to plants. Sand is essentially glass. When was the last time your window dissolved? I dunno. There's probably more chemistry to it. I doubt the sand provides much Si, and probably way less than soluble ProteKt. But, if it makes you feel good, do it (as long as it's not counter productive!). Don't use fine sand, it'll make cement when it packs and gets wet. We use pool filter sand which is pretty coarse.

 

[Eric Muehlbauer]

I think that the use of sand goes back to a mix that Ray Rands published a few decades ago. He said that the sand opens up the roots by getting between the root hairs (or are they more like scales?) and keeping them open, and, as Ernie said, giving them something to "grab on to."

 

[cnycharles]

jim marlow gave a repotting clinic last september and he showed us a paph that had sand in the media, and the sand had collected to the root hairs and the roots looked pretty happy. I wonder if it helps to keep the hairs a bit moist but keeps large droplets from bridging the root hairs and stifling things?

 

[Jim Toomey]

Hi Ernie,
Do you have a particular place that has good prices on sand?
I'm here in Maitland.
Thanks,
Jim

 

[Ernie]

Do you have a particular place that has good prices on sand?

Home Depot. Look in the pool section- it's outside with the garden stuff at ours in Waterford Lakes. It's a 50-60 lb bag for about $4-5. If you ask the employees, they'll probably send you to construction materials for play sand. If you need to ask, ask for pool filter sand.

 

[Jim Toomey]

Thanks!
I've looked before at mulch,dirt type dealers but they want to sell by the truck load.
50-60# bag much more manageable.

 

[cabnc]

Ask an associate at TheHomeDepot, they probably have a 'busted' bag on the side. Then you can get less than 50# and a much reduced cost.

Charlie

 

[Candace]

A couple of paph growers in my area put sand in their mix for the reasons stated above. I added some sand to my CHC mix this year. I figured it can't hurt.

 

[Lance Birk]

When I first made my "Pretty Good Mix" in 1964 I was always puzzled by the fact that so many root hairs stuck to the particles of sand. Since I recently began to publicly sell my mix I have done more research and can offer more clarity.

In my grower's manual I said that silica sand can be used as a substitute for "washed river sand" which is the same as is used to make cement, or plaster. It's not quite the same. Straight silica sand provides aeration and a point of attachment for nutrient uptake. River sand however, contains a multitude of nutrients, as well as silica sand or quartz, which supply necessary micro-nutrition for our plants. Closer examination shows root hairs attach to other ingredients contained in the sand besides the impervious particles. This is why, I found, that I hardly ever needed to fertilize once I began using this mix for all types of my orchids. Although I have not examined many other sources of 'river sand' I am confident that most other sources around the world will be similar in practice.

Lance Birk

 

[gonewild]

Straight silica sand provides aeration and a point of attachment for nutrient uptake.
Lance Birk

Can you clarify what you mean by "point of attachment for nutrient uptake"?

 

[likespaphs]

also, would you please clarify washed river sand or where to find it?

 

[Lance Birk]

The point of attachment is just that. It is where the root hair attaches to another body which then allows a 'solid base' from which nutrients can be readily 'up-loaded'. Rather than leaving that root hair just dangling in space, so to speak, other objects such as solid quartz particles as well as absorbent organic particles provide an attraction to which fertilizers, nutrients, etc., will attach. I'm certain you have seen how they work; root hairs always seem to attach to 'something'!

The washed river sand is readily found in home improvement centers, garden supply centers and your local building materials place. As I said, ask for the sand used to make cement (concrete) or plaster..... They call it "washed" but clays and other elements that make up "soil" are always in there.

 

[Eric Muehlbauer]

How would the aragonite (such as Southdown brand) sand that is sometimes sold at places like Home Depot be? Its fine sand, pure calcium carbonate...I use it in my reef tanks. I doubt it would be good as the only sand source...maybe too basic, but how about if it were combined with more typical silica sand sources?

 

[chrismende]

Thanks for the clarification, Lance! I've just been re-re-re-reading your second edition in the cultural sections. And specifically about the sand and moss.
I know that Terry Root uses sand in his mix, too.

 

[TyroneGenade]

...If you need to ask, ask for pool filter sand.

Do NOT ask for pool/building filter sand. This type of sand is normally acid washed. The acid dissolves out the micronutrients but this is beside the point. The acid washing allows the sand particles to link up via silicate bridges causes the sand to cake-up. Plants do not like this. Read http://www.apsa.co.za/board/index.php?topic=4337.0 for some experiences with pool filter sand for growing plants.

tt4n

 

[labskaus]

So you guys are talking about two different things:
Sand particles that may offer physical effects while being chemically inert, like Quartzite, and the clay particles which are part of most sands and which may give different chemical effects in the medium (buffering, ion exchange,...).

Sand is so difficult to describe and to standardize. I think its a try and error thing.

 

[Ernie]

Do NOT ask for pool/building filter sand. This type of sand is normally acid washed. The acid dissolves out the micronutrients but this is beside the point. The acid washing allows the sand particles to link up via silicate bridges causes the sand to cake-up. Plants do not like this. Read http://www.apsa.co.za/board/index.php?topic=4337.0 for some experiences with pool filter sand for growing plants.

tt4n

Interesting. The pool filter sand we use is MUCH more coarse than the builder's sand available here. Our pool filter sand does not cake either. On the contrary, it flows quite well compared to other kinds of sand we've tried. We tried builder's sand and (foolishly) play sand and both accumulated in the bottoms of the pots and essentially made cement- not cool. Whereas the pool filter sand stayed within the bark mix bed much better. As far as micronutes, I can live with that.

What types of sand are other folks using successfully here in the US?

 

[Rick]

Since I took it home from work I can't remember if it was play, or building sand. It was cheap stuff from Home Depot. I've used it for a lot of plant stuff, and at work I use it as a component of artificial sediment for toxicity testing.

It's pretty dusty, so it does get washed before use. However, the grain size is pretty big compared to the super fine "silica" sand. Maybe a 1/4 of a millimeter??

It also flows well and does not compact. I think the compacting issue is more due to the smaller grain size so you get tighter physical packing between particles.

 

[Rick]

The other day I thought I saw a post that said that white versus yellow play sand was dangerous because it would raise the pH of the mix.

Since I ran out of the yellow sand a couple months ago, and did a bunch of stuff with whiter sands, I did a check in the lab today.

1) A couple of tbs of a white sand (Quickcrete Play sand) in about 50 ml of distilled water turned the pH to 9.0

2) rinsing in more distilled water about 3 times and the pH dropped to about 8.8

3) One rinse in tap water (pH about 7 )and leaving the tap water in place, the pH stayed at 7.

4) replacing the tap water with distilled water allowed the pH to go back up to 8.8

It appears that there is a weak source of alkalinity in this white play sand, but it is not alkaline enough to change the pH of a moderately buffered system (Nashville tap water is only moderately hard with an alkalinity of ~ 50mg/L as CaCO3). Since I am using it in rather small quantities in bark or moss based mixes (which are somewhat acidic), it will have either no effect or slightly beneficial effect of buffering the most acidic pots.