MGMC: Is it staining my new deck?

Linda124July 2, 2012

After in-ground gardening in Zone 5 for many years, I moved to Zone 7. Now I have only a huge deck, which we just finished staining a beautiful dark stain. Decided to try container gardening. Bought a bunch of 17" diameter pots, filled them with Miracle Grow Moisture Control potting soil, planted various flowers, tomatoes, etc. Watered them all thoroughly. Next day, where one pot drained, the new deck was stained. Tried to clean it, discovered it was caustic; it ATE the new deck stain. Next day, 2 more pots' drainage stained the deck. Ran back to Home Depot, bought a saucer for every pot, but that won't work because one big rain will overflow the saucers and ruin more deck. What's in it that would cause this ruination of my deck? Is my only option to empty each pot of the Mir.Gro and find somewhere some better potting mix that won't hurt my new deck? I love my plants, but I love my husband more and he loves his new deck even more than me right now. Advice?

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greenman28 NorCal 7b/8a

This is one of the reasons I stopped using bagged soils composed primarily of peat moss.
Have you ever seen the water in a peat bog? Yeah, well that's basically what you're seeing.
I know it's a bit late this season, but I strongly recommend switching over to a bark-based
mix that won't create this nasty, dark effluent that stains wood and concrete alike.

For now, I would be careful to rinse the deck after watering every time.


    Bookmark   July 3, 2012 at 10:26AM
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I have 740 Quarts of MGMC on my deck in various pots and no staining whatsoever.

But I have my pots on plant dollys so there is several inches of AIR beneath the pot.

Has nothing to do with the MGMC, has to do with lack of air circulation.

    Bookmark   July 3, 2012 at 2:17PM
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greenman28 NorCal 7b/8a

Wrong. It's the effluent from the product itself.

We know you're a vocal "proponent" of Miracle Grow, and we're happy that you've avoided
the problems that are directly associated with this product.


    Bookmark   July 3, 2012 at 8:32PM
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I dont think someone is going to re-pot all they're MGMC containers mid season into a different soil.

Either way different soils are different and a different soil could also stain the same deck.

As MGMC is the same soil being used in two different settings and causing at least one deck to be discolored with another saying the deck isn't discolored by elevating the containers........ could deck stains be different from one deck use to the other to cause the deck discoloring of stain result ?

    Bookmark   July 4, 2012 at 5:18AM
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You can believe what you wish, I am a vocal proponent of the FACTS in front of my eyes only.

Magically I have 740+ quarts of it which I water daily and have no such staining of any kind whatsoever.
Been using it for many years with no staining.

I had a couple of pots just sitting flat on the deck prior to getting dolly's and both of them started to darken the deck underneath it in just a few days, I moved the pot and the darkening went away. I was water logging the wood which will start to mold it and stain it permanently from the lack of air circulation.
This is THE leading cause of decks being ruined.

and it has ZERO to do with what ever soil is being used.

Here is a link that might be useful: Deck Stains

    Bookmark   July 4, 2012 at 8:17AM
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Also some hardwood decks the wood itself has a high "Tannin" content. Which will react with moisture and cause black stains.
Even more so if any "iron" comes in contact with it.
Such as around the nails and also some soils are higher in iron, or you could be using something like "Sluggo" which is "Iron Phosphate" which will react with the high tannin content of certain woods.
Some can also have high iron content in their water which also reacts to the tannin's.

But most of this can be alleviated by simply making sure you have plenty of air circulation. The faster the wood dries the less chance there is of any staining.
However if you have a very high tannin hardwood and your water from your hose is high in iron you are probably going to get staining almost no matter what you do.
Unless you seal it with something like WoodGuard which I think is some Tung Oil Bees Wax concoction.

and you need water soluble iron in your potting mix as a nutrient.

    Bookmark   July 4, 2012 at 9:04AM
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Thanks everyone for your ideas. I should add a couple of facts: all the pots are raised off the decks by 2" x 2" lengths of wood, (a set of 2, parallel, under each pot.) So no pots are sitting right on the deck. About the "staining"--we put a dark brown Behr wood stain; the effluent is light in color and cannot be scrubbed away; instead it has eaten through the stain. We know we have to re-stain each of these areas.I went to Home Depot and bought saucers to put under all the pots. I know this will reduce the good drainage I wanted for my pots, as the water will stand in the saucers, but maybe catch most of the affluence. I also plan to hose the deck around each pot after each watering has had time to drain through. Getting ready for a 4th of July party on the deck today, planning to show off our gorgeous newly stained deck, but it doesn't look so gorgeous now. Any other ideas will be appreciated.

    Bookmark   July 4, 2012 at 9:15AM
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White or very light staining on a dark brown deck stain is probably minerals in the water or maybe depending on how "newly stained" the deck is and how thick the stain was applied it could just be a reaction to the water on the not 100% completely dried stain.

We had pretty good results with the Wolman Durastain semi transparent in Natural Cedar color.

Here is our deck after about 11-12 months after staining, still looks pretty good but I am sure will have to be re-stained in another year, none of the deck stains last as long as they say they do and it is better to reapply long before it starts to degrade.

    Bookmark   July 4, 2012 at 11:06AM
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Wood type for each deck was also a thought but leaning toward a more economic solution is better than some counter productive opinions being expressed

If TSP is handy you could try a small spot to see if scrubbing works TSP could also be a failing effort if I really had to say.

If a nice looking deck is important to you for guest reasons all I can add is we all have guest at one time or another guest come to visit us not our decks most times these types of problems are often overlooked by the BB-Q to the swimming pool and a soft voice explaining what had happened if asked.
A final idea is :

Have a Safe and Happy Forth

    Bookmark   July 4, 2012 at 11:29AM
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greenman28 NorCal 7b/8a

Well there you have it, the containers are elevated as Linda informs us...
which disproves the air circulation hypothesis that you so desperately latched onto.

MrLike, I apologize for the wording in my original reply - I did not mean that the mix should
be switched this season....because it's already so late in the season. What I meant was that
for next year, a different mix should be selected - a mix such as the 5-1-1 that runs clear
after watering.


    Bookmark   July 4, 2012 at 12:16PM
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howelbama(7 NJ)

I don't agree that the 5-1-1 runs clear after watering... It is peat and pine bark based as most MG mixes are too... Peat and pine bark contain tannins that will naturally leach into the water. I think that no matter what soil mix you are using, there is potential for staining the surface those containers are on. The 5-1-1 is faster draining in most cases, so maybe the water doesn't pick up as much tannin as it runs through the mix.

    Bookmark   July 4, 2012 at 12:52PM
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greenman28 NorCal 7b/8a

do your containers of 5-1-1 really run dark after watering???

I fully saturate my containers of 5-1-1 the day prior to fertilization,
then I fertigate the following day. That moisture has a good sit in the mix,
and yet when I water there's no tea-colored liquid running out.

Anecdotal evidence isn't the best, but this is what I've observed over the past
three years of full-time 5-1-1 container gardening.


    Bookmark   July 4, 2012 at 1:10PM
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howelbama(7 NJ)

They don't run as dark as other mixes, but there is definetly a tint to the water that runs out. I'm growing everything in the ground this year, so I can't go out and test. I just think any mix has the potential to stain, some probably more than others. Even the fertilizers are usually dyed with some coloring, so that alone can cause staining. Elevating the containers and giving the area underneath a rinse is always a good idea in my opinion. my decks are crap though, so I don't really care at this point lol...

    Bookmark   July 4, 2012 at 2:37PM
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Doesn't disprove a damn thing.
She isn't even having dark staining, it is light colored like you would have with just plain water.

I guarantee that if you place a pot flat on a deck with no air circulation you WILL get dark staining from mold/mildew, dirt collection that will keep the wood moist longer etc.
Plain and simple and it doesn't matter what kind of wood you have or pot or mix, some may be worse than others but your deck will stain and eventually rot.

The water coming out of my pots certainly isn't "tea" by any means, I have never noticed any tint to it at all really but I have never captured it in a white container to check.
Either way we have zero staining of any kind white or otherwise.

Could also be that our deck dries faster due to it being 20' in the air with plenty of gap between the boards.

I imagine there are numerous variables, but one 100% certain way to stain and rot your deck is putting pots or anything else flat on your deck for months on end.

    Bookmark   July 4, 2012 at 4:15PM
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greenman28 NorCal 7b/8a

I think Linda has her answer at this point.

No need for you to continue in this rude fashion.


    Bookmark   July 4, 2012 at 4:45PM
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LOL, ditto.

    Bookmark   July 5, 2012 at 9:10AM
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It's been a fun and educational discussion, guys. thanks.

    Bookmark   July 5, 2012 at 8:43PM
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A person saying even a mix may also stain and only two brands of stain have been mentioned to date.

Drum roll please::: what stain other than is being used on the other deck is being stained by container run off Howel ?
With a mix soil of costume type (5-1-1) no run off stains on his deck what stain is Josh using on his deck ?

Nunya: You had them with the pic but you added more than you may of wanted too. Caution on internet guarantees or a word of warning It's peps like me that want you to send the check out first When check is received and bank has cleared then Ill water run off via a container passing it though an elevated catch I say this cause if there is one person who can mess things up and really bust them bubbles.... Well how am I doing ?

    Bookmark   July 6, 2012 at 1:55AM
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