Diatomaceous Earth as a seed starting medium

[travis]

Several years ago, I used diatomaceous earth product as a portion of starter mix, along with peat making up the majority of the remainder. The DE was an oil absorb product I bought at Rural King in a large bag, I believe was about 50 lbs., and much cheaper than what Ray indicates today's price may be. But then there's the immense increase in mining, drying, processing and shipping costs over the past few years to consider. The material was baked, and was much whiter than what Ray shows in his pictures.

The only problem I had was algae growing on the DE, but Ray's photos don't seem to show the same problem.

I think I'll try DE again next year, but go 100% DE as Ray did, water solely from the bottom, and see how it works for me. I'd really like to use something besides peat, vermiculite, perlite, and coir, all of which have posed various problems for me either with regard to cost, function, or sustainability.

[RayR]

The color of DE does vary, it's not always pure white. There are impurities that will account for the color—minerals and volcanic clay particles. The UltraSorb is much whiter when it is dry, but when you add water the earthen tones really come out. The UltraSorb is baked too at about 600°F from what I've read, to dry and sterilize it, but that doesn't alter the color, and it doesn't alter the amorphous structure of the silica. Calcined DE like what is used for pool filers is heated to a much higher temperature near the melting point which changes the structure of the DE and creates a lot of unhealthy crystalline silica. Never us that stuff.
My main concern was choosing a natural amorphous fresh water DE that had the proper PH for a seed starting medium.

Travis, I have had algae growth on the surface of the DE, but only when I used rain water. It didn't occur when using distilled water. It didn't show up much with the Tomato's though. Luckily the algae is harmless. Fungus won't grow on DE since fungus needs dead plant matter to grow on, which is probably another advantage of the DE—no chance of damping off.

[travis]

This is all very interesting.

First of all, originally I was only familiar with diatomaceous earth (DE) as a water filtering medium.

Secondly, I was under the impression that all DE was calcareous, fossilized, single cell skeletons of some ancient diatoms (hard shelled algae thingies).

I did not know they are siliceous. I was worried that using too much DE would raise the pH of my mix. So, I should be looking for what in particular info on the package to indicate pH below the 7.0 neutral point?

[RayR]

DE is not calcareous at all, at least not the UltraSorb, there may be trace amounts of calcium Carbonate in there but Diatoms make their shell out of silicon dioxide. I think the closer you get to a pure DE deposit, the closer to a neutral PH you will get. I don't think you are going to find the PH specified on bags of DE sold as absorbent products, I only verified the PH of the UltraSorb by testing it with my PH meter.
You could use a horticultural grade DE which naturally would require it to be around a neutral PH, but at least around this area you are only going to find it sold at a hydro store in a granule size about like Perlite.

[travis]

I'll just get the auto oil absorb product and go for it! Thanks for the info, Ray.

[RayR]

One week has gone by since my last post on the pepper experiment and tonight was the night to take a closer look and pot them up. All the seedling are healthy and have grown some, the seedlings grown in the DE still outpaced the seedlings in the Jiffy Mix. Besides being a bit taller, the leaves were noticeably larger and the stems thicker and like the tomatoes, the root mass was larger and more fibrous.
I'm still thinking the next time I do this I will start the seeds in 2" or 3" cells instead of the 1.5" cells I used this time. More space with less root competition could yield even better results.

[rsrb]

Would "Fuller's Earth" also work? It's similar, and also marketed as a cat litter product (7 lbs for $1 at the local, um, dollar store) but haven't done enough research to determine whether it might also be suitable for plants. The Moltan products, even at AutoZone, do at least mention planting on the label....

[janezee]

Way to go, Ray! Thanks for the update. I will try this out for sure!

j

[RayR]

Originally Posted by rsrb

Would "Fuller's Earth" also work? It's similar, and also marketed as a cat litter product (7 lbs for $1 at the local, um, dollar store) but haven't done enough research to determine whether it might also be suitable for plants. The Moltan products, even at AutoZone, do at least mention planting on the label....

"Fuller's Earth" is a name that is used broadly to include many forms of weathered volcanic clay. You could have 2 different products claiming to be made from "Fuller's Earth" and both can have totally different properties and mineral composition.
If you could find a clay that had similar properties to DE (soft rock-like structure, stable in water and a near neutral PH), then it might work, but I haven't found one like that yet. They all tend to be lower in PH, 6.0 and under.
For instance, Moltan's other cat litter and oil absorbent products that are not DE is made from Montmorillonite Clay that is from their mine in Tennessee. I got some of cat litter version, it is a hard non-swelling clay, stable in water and absorbent but it tested to be a PH, of 4.8. Just for fun I tried a side by side comparison growing onion seeds in it and DE. I was actually surprised that the onion seedlings germinated and grew in such an adverse PH situation, but they didn't do very well compared to the onions in the DE. (See picture, this was at 30 days from seeding)

[Tracydr]

My husband stopped at Autozone the other day. I was waiting in the car and saw the oil sorb in the front window on sale, nice big bag. I almost went in and bought a bag, since I'm out of seed starting media, except for my Jiffy pots.
I may go back and get some for my fall starts, it's getting close to time to think about things like celery, artichokes and maybe Brussels.

[RayR]

Originally Posted by Tracydr

My husband stopped at Autozone the other day. I was waiting in the car and saw the oil sorb in the front window on sale, nice big bag. I almost went in and bought a bag, since I'm out of seed starting media, except for my Jiffy pots.
I may go back and get some for my fall starts, it's getting close to time to think about things like celery, artichokes and maybe Brussels.

The UltraSorb is the DE product, AutoZone sells it in a 15lb bag. AutoZone also sells the Moltan clay absorbents in 8lb and 33lb bags, you don't want those.

It's interesting to see what seedlings work best in DE, I suspect some will do better than others, although my experiments with onions, tomatoes and peppers turned out well, my basil is not working out well in the DE for some reason.

[Levent]

Here are 2 examples of my experiments on germinating seeds in diatomite.
First photo Ocimum gratissimum 2.4.2011
Second photo Ocimum gratissimum 26.5.2011
Third photo Solanum abutiloides 15.4.2012

[RayR]

Looks good Levent. Did you notice any difference in growth with the Basil in DE and in whatever seed starting mix you normally use?
What do you do with the Dwarf Tamarillo anyway?

[Levent]

Hi Ray,
I noticed the difference ten years ago!Since then as germinating medium I have used only diatomite.I grow mainly house plants (Stapeliad and Hoyas) in diatomite using simple hydroponic techniques and also some edibles for fun and consumption.S. abutiloides is a novelty for me this year.I plan to consume ripe pods (they're edible) I transferred two plantlets to garden, one to pot culture (ıt's under a porch facing south) one to subirrigation pot (it's in greenhouse) all the rest were donated to relatives.The one in pot culture heads for now and has buds on apical shoot.

[meadowyck]

I have only been involved with DE for getting rid of the fleas that my collies picked after we moved here, and of course keeping the ants out of my house up north. I love when a product has multiple uses.

Thanks so much for sharing your results. I'm gearing up to for seeds next month and I think I'll try some seeds in it.