They will provide calcium, maybe a bit of salt. Unless the tree is a small Magnolia or something that needs acidy soil, you will likely not notice any change.

It's a Beach Plum, that likes salty sandy poor soil. The shells themselves *MIGHT* buffer acid and provide calcium...*IF* they break down. If the bird doesn't clean it's plate, a small trace of clam might be left, that could provide nitrogen and attract bugs. Does that make sense? There is also the risk of physical damage. Not sure why so many clam shell are right in this spot.

I assure you, they will break down. I go to the old home in ME almost every year and bring back lobster, clams, etc. and spread the shells on the lawn and in the garden. The grass is a bit greener where I spread them, but that is mostly because the area I spread them is a clay pan with a veneer of grass over it. I do not fertilize lawns, unless you count the seafood residue i spread. Why fertilize a lawn, it means you'll have to mow more often.

BTW, I have 2 Prunus maritima (if that is what you mean by Beach Plum). One has 3 plums, one has 300. Both planted the same time, growing about 8 ft. apart. I should be happy both don't have the fruit (we don't use much of the fruit), but they are starkly different. Maybe I'll re-open the post and put up a pic later.

Beach plum (Prunus maritima) is a shrub, not a tree. Grown along the New England coast where it is subjected to adverse conditions including clam shell attacks by birds it has the ability to fight its way through sand blown dunes, sending out new growth and roots. It is a tough survivor, one of those plants I describe as the 'glue' that hold sand dunes together. Planted inland in more protected areas Prunus maritima is a pleasing shrub growing to about 5' in height which needs a companion if good fruit is desired.

I have a few minutes so will add some additional information. There is a renewed interest in nursery Beach plum cultivation for the home gardener. Back in the 1950's a number of named varieties were introduced and the collection was planted in the Arnold Arboretum for future reference. That collection was removed for some unknown reason. The fairly recent sale of the MA Horticultural Society's complete library resulted in the loss of the hybridizer's notes. There is a horticultural writer who has been searching for them.

For those of you growing or picking the wild Beach plums, pay attention. The only Beach plum problem is that it does not fruit consistently year after year. There is still a large award available from the MA horticultural Society for anyone who can submit a bush that has done so for many years. The Society may have forgotten about this award, but it is there lurking for some keen observer to claim.

I like the concept of "edible landscaping". I like native plants because they are Earth Friendly. I'm a lazy gardener.

Paw Paw and Beach Plum seem to be among the only native plants that make fruit larger then a berry and which I don't consistently kill. Beach Plums have the added benefit of salt tolerance. (My parents lost a lot of trees to salt spray). I planted two potted ones (doing great despite neglect) and two bargain-basement bare root ones (surprisingly not yet dead...I have bad luck with bare root saplings). I was hoping that inland they would grow into small trees...

The county soil conservation office sells batches of ten really cheap in the Spring. I missed this year's sale, but if these four survive the summer and winter I may buy a batch next Spring. Use them for erosion control and property line marking.

This post was edited by edlincoln on Sun, Jul 21, 13 at 11:15