What is the effect of putting oyster shells or other shell on potted plants??? Some plants thrill and grow very fast - Why?? Some plants will die - Why???
Hi Barbgup: Most people will use oyster shells to add Calcium either to correct a chlorosis problem or thinking that the oyster shells will help improve drainage or to improve soil pH. For usage on potted plants it depends entirely on what plant and where is it grown such as indoors or outdoors and the relative size of the shell, either large and coarse or ground almost into a powder. There are plants that respond well to oyster shells such as Azaleas but it seems best to use the oyster shells for Azaleas in the ground. I believe right off hand that Blueberry growers use oyster shells as well. On the other side of the spectrum are plants that do not like the oyster shells at all such as Quercus palustris that tends to have a strong aversion to Calcium. Oyster shells can contain as much as 36% Calcium which is quite high a percentage. Some plants do well and some will be killed off due to the plants sensitivity to mega doses of Calcium. I would prefer to use oyster shells on select "acid loving" plants grown outdoors rather than on alkaline tolerating plants. I would not use oyster shells on ornamental plants at any time as the microbial breakdown of the shells will take too long and the release of so much Calcium cannot be adequately countered by the indoor growing plant. What happens when we give a plant too much Nitrogen? We kill off root systems. Well, the concentration of Nitrogen is generally much less than the amount of Calcium from the oyster shells and perhaps other shells as well applied to the roots. The root systems in many cases will not be able to handle so much Calcium, either all at once or even at timely intervals. Jim
