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Gardenia soil -- too basic

Posted by tonyb416 z5-6 NJ (My Page) on
Sun, Oct 12, 08 at 17:32

So I recently repotted a small gardenia and watered it with Miracle Gro Rhododendron and Azalea mix, but a significant portion of leaves turned yellow. I just tested the soil and its pH was nearly 8! Too basic! How can I get back to the correct pH? I suspect I did not combine the right amount of water and soluble mix in the watering pot. :-(
And should I be using fertilizer in October or should I hold off until the spring?

-- Tony

Follow-Up Postings:

RE: Gardenia soil -- too basic

After some investigating some collegues and I had determined the MG for acid plants actually has NO ingredients that acidify the soil!(go figure)
The use of a bluing agent for Hydrangeas will drastically
lower the PH of the soil in question and help with the plants health.
It's definitely the end of the fertilizing period for Gardenias- resume heavy feeding in late March.

RE: Gardenia soil -- too basic

>> the MG for acid plants actually has NO ingredients that acidify the soil!

Get out! So would I stick with the old gallon of water + 1 table spoon of white vinegar to help acidify the soil or would it be better to mix in some compost that has a healthy dose of coffee grounds? Or some variation of both? :-)

Thanks for the info, omniphasic!

-- Tony

RE: Gardenia soil -- too basic

  • Posted by jimshy z7 Brooklyn, NY (My Page) on
    Tue, Oct 14, 08 at 18:12

If you used just regular potting mix, it often has powdered limestone added to keep the ph neutral. If you can mix in some peat moss, composted or chopped up oak leaves, or crumbled pine needles, that would help. I wouldn't use coffee grounds in the soil, it's too fine and won't help drainage, but you can mulch around the top with grounds, or any of the other materials. Go easy on vinegar or other chemical amendments right after repotting, you can do more damage to the roots than the incorrect soil ph will do. Also, don't overwater while the plant's getting used to the new pot, you can rot a gardenia easily that way. If it lives despite all the extra tinkering, you're doing great!


RE: Gardenia soil -- too basic

If you potted your gardenias in typical bagged potting 'soil', the pH should be fine. Peat based container mixes are slightly acid, due to the nature of the product. Even if lime is added, the pH will still be slightly acid to neutral. Home pH testers, however, can be quite inaccurate.

Acid loving plants require IRON, which your MG fertilizer has plenty of. (Truthfully, acid loving plants should be called 'iron loving'.) In garden soil, iron is typically found in plentiful amounts but is 'locked up' and away from the plants, unless the pH is on the acid side. However, your peat based potting medium will have no iron in it whatsoever. You can lower the pH all you want to and it won't do any good. Thus, adding it in the form of a chelated iron is the only way your plant will benefit. I'd not even worry about the pH. Your MG product is doing just what it is supposed to do. (Which is to provide iron, not change the pH.)

The 'bluing agent' for hydrangeas is actually aluminum. That, too, is another element that becomes available to plants when the soil is on the acid side of the pH scale. But aluminum products can be added to the soil to encourage the blue coloration. Aluminum sulfate should probably not be added to a container just to alter the pH.

Pine needles and oak leaves do very little to alter the pH of a native soil, and would have no effect on a good soil-less potting medium. A great potting mix doesn't have the microorganisms to break down the particles, nor do we need it to.

Have you just brought your plant inside from a long vacation outdoors? Any other changes, other than the repotting, that the plant has been through?

RE: Gardenia soil -- too basic

So...What can one due to lower the ph in a soiless mix especially for gardenia to make sure that our plants are getting the proper uptake of nutrients and iron....
When you first start with fresh soil, the ph is pretty good. But after a time it changes especially with facet water that is nuetral.....

RE: Gardenia soil -- too basic

I add peat to the soil when it's mixed and potted.
A teas of vinager per gallon of water will lower the pH. Don't know about tea or cofee grounds, there's too much controversy whether or not it works, causes rot, and attracts rodents.
One thing I do is toss used tea bags in gallons of water. I leave them in the water until it's time for a drink. IT may or may not work, but can't hurt. Toni

RE: Gardenia soil -- too basic

Well after feeding the plant with MG, a good number of leaves turned yellow and most fell off.

Right now, I'm just misting, keeping a circulating fan on the gardenias and other citrus plants, and keeping them in a southern facing window. Most are doing well and it looks like the gardenia is starting to bounce back.

Looks like the citrus and other fragrant plants are ready for a long winter's nap!

Thanks all for your feedback~
-- Tony

RE: Gardenia soil -- too basic

I suspect that the problem is because you've brought them inside for the winter, a rather traumatic change for gardenias. And Tonyb416, it's very important that you read and follow the directions for mixing soluble fertilizers....most people use much less than the label calls for.

By the way, the cooler the better for your plants. Heat not only lowers the relative humidity, but these plants just seems to do much better in a cool room.

How much vinegar you use depends upon the pH of your faucet water. Call your utility (or water) provider to find out what the average pH is.

Mike, you don't really need to lower the pH to make sure your plants are getting those essential elements. YOU provide them in your fertilizer.

RE: Gardenia soil -- too basic

>> How much vinegar you use depends upon the pH of your faucet water. Call your utility (or water) provider to find out what the average pH is.

My utility is my well. I'd have to send a sample out to NJ Analytics Lab ;-)

Thanks for all your advice.

RE: Gardenia soil -- too basic

Hi Toni!
I have been using vinegar with that gardenia I have, and so far it's doing pretty good (better whisper that). All I use for fertilizing it is a little bit of liquid iron with trace minerals. I go light on it of course, only fertilized it once so far. I stuck mine in regular potting soil. Amazed it's not dead yet, ha ha! I hope everything works out for ya! :D

I took my large key lime plant inside, and a ton of it's leaves are turning yellow and falling off, it's not getting enough sun.

RE: Gardenia soil -- too basic

Hey Mersipoo..haven't seen you in ages..Where've you been hiding? Are you hibernating? Gone dormant till May? lol
I'm happy your Gardenia is doing that the same denia you posted about 6+ months ago? If so, that's good to hear, I remember you complaining how much work they were. lol.

Mersi, I know ppl who use vinegar and swear by it, the same applies to Epsom Salts.
One old plant book says, to prevent soil from turning alkaline, (especially as it ages) add vinager once a month. One book says 1/4 teas per gallon of water, for a once a month schedule, the other books states, 1 teas every 5-6 months..
Speaking of pH, it's time to test potted plants..we had a lot of rain this summer.

I have no idea of a proper feeding routine is for plants grown in z8 and up, but for those of us who live in cold climates, z6 and lower, plus cloudy days, fertilizing should be stopped. Force-feeding a plant is no different than force-feeding a human while asleep, but that's my opinion.

By the way, I'm whispering, Mersi, as I'm sure you're tapping keys softly..:)

If you have a current pic, please post..Toni

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