Oyster shell mulch

fredfig(7)May 8, 2010

Fig trees on Ocracoke barrier island, N.C.

Just an overgrown sand dune base and salt spray, but the local families have been growing figs since the 1700's.

Last summer, one lady "put up" 428 pounds of figs and made lots of fig cakes.

In December 09,"root cuttings" , one of our Forum members had a thread about Nematodes and lime/oyster shells.

On the island, the fig trees are heavily mulched with oyster and clam shells.

Considering sandy soil and nematodes , then seeing many 8 ft. trees , there must be some truth in using oyster shells / limestone as a preventative.

Plus, they must help keep roots from freezing.

I do not know, but the trees are growing and producing figs, in most every yard. So, I am going to the docks and get some shucked shells for my new trees. Fred

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Yes, any good calcium carbonate source (concrete, limestone, oyster shells, clam shells, crab shells, etc.) seems to work at holding nematode populations at bay.....to where a fig tree can tolerate them and produce fruit. I had picked up this information from the owner of a southern nursery who reported very good success with this method in his opererations. I reported it on this and the other fig forum quite some time ago....never received any feedback. Thanks for posting this confirming information. It definitely can be helpful to some fig growers......crushed limestone is reported to be real good where it is available.


    Bookmark   May 8, 2010 at 1:54PM
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noss(Zone 9a Lafayette, LA)

Hi Fred, That's real interesting how those figs survive amidst all the salt spray and sand. The shells must also have salt in them, too, but evidently it doesn't harm the fig trees. I've always been told that plants don't do well around salt.

Dan, For my inground trees, do I just put the shells around the base of them? Do the shells need to be crushed? Is there any other thing, such as magnesium, or anything else that is needed to go with the shells, or limestone?



    Bookmark   May 8, 2010 at 7:35PM
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This could be expensive but crushed coral should work as well then for the calcium.I'm thinking a couple pounds in each 15gl or larger pot. Also, When I had my marine/saltwater tank I used to add liquid calcium to boost the calcium level for the coralline algae.

What do you think?


    Bookmark   May 8, 2010 at 9:22PM
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All of this is new and no one on this forum yet has any real definitive answers on how to deal with nematodes. It takes people like those on this forum wanting to try this out and reporting back their results. I have no first hand information other than what I've been told by a very reliable source. I want to believe what he told me...but have no definitive proof yet. Many Southerners who have to deal with nematodes will plant their fig tree near a concrete slab or right next to an old building.....it has been reported that fig trees thus planted can reliably fruit even when infected with nematodes.

If I had an already infected fig tree in my yard that I was trying to help deal with those nematodes. Here is what I WOULD DEFINITELY do.....

I would get me some good soil from an uninfected area and mix it some crushed limestone chips (or clam shells from Lake Pontchartrain).....these are available in our area if you look around. I would mix my soil and the limestone chips in a cement mixer. (Yes, this fig nut has one just to mix his potting soils, rooting mediums, and other secret stuff.) I would pour this mix around my tree...in effect building a mound of new soil/limestone around my tree. New roots will grow into this new soil and hopefully receive some of the benefits of the limestone. If my infected tree continues to thrive and produce fruit for me....I would consider it a success.

There are no damaging salts in oyster shells. Sea water salts can definitely damage trees if they are left to build up and not washed out by the rain or watering's.

FYI.....I have planted a trial row of my fig trees right on top of an old driveway of mine that was composed of just those small clam shells that were dredged from Lake Pontchartrain and sold for many years. My trees seem to love it. I can see no problems whatsoever when planting fig trees into an existing clam shell bed.


Yes, Coral is high in calcium carbonate.


    Bookmark   May 9, 2010 at 2:46AM
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....one other thing. Someone had reported on another thread that the stuff they feed to chickens to ensure their egg shells (which is pure calcium carbonate) remain hard and tough after laying.... is composed of oyster shell bits.


    Bookmark   May 9, 2010 at 3:01AM
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You can go to any feed store or grain elevator and buy 20lb bags of crushed oyster shells. It is what is mixed in with grind and mix chicken feed orders. It's really cheap.

    Bookmark   May 12, 2010 at 1:25AM
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I wondered about the salt in this area also. The hurricanes and strong North-easters do blow sea water across the island.
But, lots of rain does "probably" wash the salt out , since the sand drains fast.
I have two , Beer's Blk and a LSU Gold, ready for planting in the yard. I did sprinkle some crushed oyster shells into my pile of "hole-filler" dirt. So, we will see
what the results are.

    Bookmark   May 13, 2010 at 9:24AM
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NO, Fred, NO!

Go buy yourself a fifty pound sack of crushed oyster shell at the feed store. Your wife will let you back in the house. I promise you that if you take home a couple of sacks of fresh oyster shells she will not let you back into the house until the stink wears off.

Not only that, but the fresh shells have razor sharp edges that you will not want to tolerate.

    Bookmark   May 13, 2010 at 2:43PM
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Oxankle.... Too late ! I bought 5 pounds of crushed oyster shell at the feed store.
BUT... I went to where oyster shells are collected.. They are in big piles and are used to spread on bottom , so the young oyster larvae have something to cling to and grow.
So, I now have both. Maybe, Fabreze will help ????

    Bookmark   May 13, 2010 at 5:47PM
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noss(Zone 9a Lafayette, LA)

Thanks Dan, for your thoughts on the shells and nematodes. Interesting that calcium might repel them. Will file that away. I thought my Celeste in the back yard showed some nematode formation on the roots a couple of years ago, but in looking the tree over this year, I saw only healthy, fine, smooth roots. When I saw the lumps in the few roots, back then, I pulled them up, as there were not a lot of them. They were attached to a sucker baby fig. I tossed it with the roots. I was probably mistaken, or I would most likely still see some lumpy roots. Don't know.

I need to get some nutrients on the big girl! She's getting ready to jettison some figlets. They are getting soft. I hate when that happens. It's been really dry here already. Last Spring, it was rainy and the figlets were all over the tree, but then it dried out and she dropped so many of them even though I was watering her.

It will be interesting to hear how the figs planted in the shell bed does.



    Bookmark   May 13, 2010 at 10:10PM
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I will be planting another trial row of fig trees later this year into another old clam shell driveway of mine. When I constructed a driveway to my first house in 1974, it was built eight inches thick using those small clam shells that were dredged from a local lake. Money was real tight for me at that time. I sold that old house and built another one in 1978 on the other end of my property. The old clam shell driveway is now covered with some nice new soil that built up over the years. I will soon put this area to good use and will have another row of 25 new fig trees added to it before winter. More fig trees for me to study their growing and fruiting characteristics......

From my fig research activities....

It is VERY IMPORTANT to keep the ground ALWAYS MOIST around young in-ground fig trees during the first couple of years after it is planted. It is more important to the development of the tree than fertilizer. However, several light dosages of 8-8-8 fertilizer does help the tree to develop quickly. It should not, however, be applied too late into the growing season as trees that are fertilized too late into the season are more prone to winter cold damage. Fig trees that are "clone propagated" DO NOT HAVE TAP ROOTS that can grow deep into the soil to seek water and nutrients. The feeder roots that develop on young fig trees are right near the surface of the soil where they can be easily damaged. Let the ground dry out too much and those hair like roots easily dry out and become dysfunctional. By keeping the soil always moist, you will quickly develop a large & healthy root system on your tree. Bottom line.......young in-ground fig trees will grow much faster and produce fruit much sooner if you simply keep the ground ALWAYS MOIST during its early years of life.

For larger fig trees........
It is also important to not let the ground get too dry even in late winter/early spring. As you know, some of our winters can be quite warm and mild in temperature with little to no rain. Those high pressure systems that come through our area can quickly dry out our soil. Whenever you see "soil cracks" developing in the ground around your fig tree......IT IS ALREADY TOO DRY. A large in-ground fig tree needs water too in dry winters and early springs for it to achieve its full "productivity potential". Those watering's should be discontinued just before the fruit are ripening, so that it does interfere with the ripening process or actual taste of the figs.

Next year before bud break, fertilize your "big girl" with some 13-13-13 fertilizer and you will be simply amazed how she will respond. I have seen some fig trees in your area that were fertilized in this manner. They had an unbelievable amount of figs on them. I can still picture in my mind the huge quantity of figs that were on an old Alma tree. The old trees in that orchard all responded to the application of that fertilizer. I with that I had my camera at the time to document the productivity of those healthy trees.


    Bookmark   May 14, 2010 at 12:33PM
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A variation on this topic, I'm not sure how it will be taken.

We save our eggshells. Our backyard "orchard" is small, so it doesn't take much. It's amazing how much the eggshells pile up. I have a big mortar and pestle, and crush the egg shells into little pieces, then save them in a small bucket. In a few weeks, I have a couple of pounds. Over a year, it makes an impressive bucket of crushed eggshells.

This seems like it is really just oyster or clam shells, that have been re-processed through hens. The consistency might be finer than the original shellfish shells.

I spread the eggshells around my fig trees, and on the tomato patch, to increase the calcium.

I don't know if this is good or bad, but it appeals to my midwestern ingrained frugality. I read that Pacific Northwest soils are calcium deficient due to rain leaching, so need additions of lime, but have not had my soil tested (I know, I'm a bad gardener).

Some of my coworkers sometimes bring me bags of eggshells, because they know I'm odd and it's a no-cost way to keep me happy. Sort of.


    Bookmark   May 14, 2010 at 12:57PM
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Those eggshells are a great source of calcium carbonate and will not cause any harm to your trees.....only benefits. I fully understand your pleasure in tending to your fig trees by collecting, grinding, and lovingly giving them those eggshell bits.


    Bookmark   May 14, 2010 at 1:09PM
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as a small child my grandmother used to take me in her garden in chicago with box of egg shells for me to break up and spread around her veggies and fruit trees along with all sorts of different peels like potato peels , banana peels, coffee grounds.
She had a wonderufl big inground fig tree as well and was my inspiration into the world of gardening.
Used to get bit up pretty good from mosquitoes and once back in the house out came the olive oil.

    Bookmark   May 14, 2010 at 3:54PM
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noss(Zone 9a Lafayette, LA)

Hi Dan,

Thanks for this information. I've printed it out for reference. Is it too late now to put fertilizer under the tree?


    Bookmark   May 14, 2010 at 10:14PM
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I use the potato peels, banana peels, and coffee grounds too. Sounds like your grandmother knew how to garden!

    Bookmark   May 15, 2010 at 11:51AM
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Chickens don't have teeth, so they can't chew the food they are given. (I think they eat corn?) So farmers will mix in small rocks in the feed. The rocks act as teeth and grind up the food, so the chickens can digest it. It certainly makes me feel fortunate for having teeth. I wouldn't want to have to eat rocks. Anyway, I think for most of the country, bits of granite are mixed in. But for coastal areas, the crushed oyster shells are used. I live on the coast, and at my local feed store, all they sell is crushed oyster shells.

I am new at figs. But I have a few growing, and mulch with a mixture of compost, manure and crushed oyster shells. Seems to be working.

    Bookmark   May 15, 2010 at 8:57PM
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I'm not a chicken rancher but I used to have a collection of yard birds....chickens, guineas, geese etc. when I was a kid. The small rocks are indeed for the gizzards but the shells are for additonal calcium to make egg shells stronger. So they don't serve the same function. Oyster shells tend to fkake apart and I doubt they would work the same way in the bird's gut?

I think I am going to try and find a weathered pile of oyster shells and use them to "mulch" a fig laying them flat around its base trying to overlap completly to help keep the grass down and see how it works out.
Yes, I know being flat they tend to lay flat... but being careful I can make them go further.

    Bookmark   May 18, 2010 at 7:41AM
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Here on Lake Michigan there is an invasive little thing called a zebra mussel. The shells wash up on the beaches so much that you can't hardly walk on the beach barefoot anymore. I think I need to go down to the lake and shovel up some shells (each shell is as big as my thumbnail).

Little John

    Bookmark   May 18, 2010 at 8:49AM
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Today we bought a bag of oyster shells. Was advised that oyster mulch worked wonders controlling slugs and snails.

Will the shells do the same thing? If used sparingly, should we be concerned about the soil changing?

    Bookmark   May 13, 2011 at 7:05PM
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Oyster shells WILL NOT change your soil's pH , if that is what you are concerned about......

Semper Fi-cus

    Bookmark   May 13, 2011 at 7:47PM
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I have a friend who plants his garden in sandy loam soil.
He plants his Okra in a clay spot 10 acres away, because clay hurts nematodes.
I am not sure how this works or if it does, but he has had a good stand of Okra in N.C.,S.C. & Ga.
I use coffee & tea grounds to stop slugs, it works for me.
Hope the crushed shells work.

    Bookmark   May 14, 2011 at 10:36AM
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