What effect do dissolved sea shells have on alkaline soil?

Fredericksburg, TX(Zone 8a)

I put some sea shells in one of my rose beds once for decoration. It took awhile but the eventually dissolved. DH thinks the alkaline soil here caused that. I'm wondering if our hard water had more to do with it. And I'm wondering if the calcium that came from them could be what killed the rose?

Also if I used lava rock instead of sea shells would they dissolve and make the soil more acidic?

Thanks, Mary Lee

Anne Arundel,, MD(Zone 7b)

I think your chemistry is a little off. Sea shells would be alkaline, and be dissolved by acid. Enough calcium to kill the rose.? I don't think so myself but I am bad at roses and have much different conditions than you do, too. Lava rock, I don't think will dissolve at all.

Houston Heights, TX(Zone 9a)

The seashells probably raised the pH of the soil and roses prefer soil on the acid side like azaleas, camellias, etc. The alkaline pH could have made it hard for your roses to survive.

Bay City, MI(Zone 6a)

...... AND, adding only Ca (seashells are almost all CaCO3) can make it difficult for the plant to take up Mg (an antagonistic deficiency), a key element in the process of photosynthesis.


Dublin, CA(Zone 9a)

How many is "some" seashells? If there were just a few they wouldn't have raised your pH noticeably or added very much more calcium to your soil. Your soil was already alkaline and already probably had a fair amount of calcium in it from your hard water, so the shells may not have contributed very much on top of that. Without any other info, it's also hard to say whether your soil composition played a role in the rose's death--there are lots and lots of other things that can kill plants (overwatered, underwatered, bugs/diseases, underground critters munching the roots to name a few).

Fredericksburg, TX(Zone 8a)

thanks for all your answers. They are appreciated. There were probably just 2 or 3 shells, maybe 3 inches long.

It does make more sense that acidic soil would dissolve them and that I know I don't have even though I added about 4 inches of compost and all kinds of other stuff to bring the ph down. We do have moles in our yard, but I don't know that we've had trouble with them in that particular spot. I knew that roses would be a challenge here, but some of them are doing well. I guess maybe that one was just not as strong.

Houston Heights, TX(Zone 9a)

2 or 3 shells???? I was envisioning that you had applied it like mulch! Also, I can't imagine sea shells dissolving in a lifetime. Im surprised. Cam

Fredericksburg, TX(Zone 8a)

I was surprised too. I'm tempted to put some more out in the yard somewhere not near a rose and see what happens. Have to find a spot where the lawn mower won't chop them up.

Houston Heights, TX(Zone 9a)

I have often wondered how acid our rain is here in Houston. I used to have a fish pond and every time it rained hard, some of my fish died. It could have been due to many things but it did get me wondering about the rain.

BTW, I use a product called Ironite to lower the pH of my soil if I need to move the pH a lot. It wont burn plants and the label says it un-chelates minerals in the soil so that they are more available to the plants. Ive used it many times. Once I get a bed about right, I can then maintain it using humus, leaf mold, etc. It also helps to use harvested rain water for your plants if your water supply is on the hard side. If only one rose in a bed is affected, that says one set of culprits to look at, but if all are affected, that's another set. Cam

Frankfort, KY

What would a 5 gallon bucket of clam and oyster shells dissolved with muriatic acid do for (or against) the soil in my 2 - 16' x 16' raised bed vegetable garden? TIA

Anne Arundel,, MD(Zone 7b)

Do you know how to test pH of your resulting bucket of solution? Isn't muriatic acid strong? If it's far on either end of the scale, you would risk throwing off the soil pH at least temporarily.
What benefit are you seeking?
I will guess your soil is basic already, (limestone) so putting shells right in the garden would not help pH. I don't know if they'd even dissolve. I have a couple big clam and oyster shells in my acidic East Coast garden, they don't dissolve very fast at all.

If you want some microminerals from the ocean or bay they grew in, you can buy them- Azomite.
If you want to keep them in the yard because they are 'organic,' that's great but I don't know there's any huge benefit.

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