Thanks for your question.

With respect to planting a plum pit, two factors need to be considered.

1). Depending upon the variety of plum tree you have, it may either be self-pollinating or cross-pollinating. If it is self-pollinating, any tree resulting from the pit should show a strong resemblance to the tree you currently have. If it is cross-pollinating, it would be difficult to predict what kind of tree would result from the pit. In fact, the pit may not be able to germinate at all. See:

https://www.skynursery.com/wp-content/uploads/2021/08/Pollination-Chart-Plum.pdf

2). Your plum tree may have been grafted. If so, any tree resulting from the pit may not be as productive as what you may currently be experiencing. This would also be the case if your current plum tree is a hybrid plant. See:

https://www.gardeningknowhow.com/edible/fruits/plum/planting-plum-pits.htm

See the following for further information on planting plum pits:

https://www.wikihow.com/Plant-a-Plum-Seed

https://gardenerspath.com/plants/fruit-trees/grow-plum-pits/

Good luck. Please get back to us if you have further, related questions. Thanks for using our forum.