Cremation - Ashes
Generally in funeral service etiquette the ashes can be scattered in a garden of remembrance, or a favorite spot chosen by the deceased, they can be buried in a churchyard or cemetery or kept in an urn.
You need to check the law with regards to the scattering of ashes on ordinary land, ocean or in rivers. There is, however the issue of consent being needed to put something on someone else's land.
If you are placing ashes in your own garden then there is absolutely no problem. Remember that you may move from that house in the future.
It is important to make quite clear your wishes about the ashes. If no wishes have been expressed, it is the responsibility of the crematorium staff to contact the relatives before disposal. Arrangements can be made for the placing of a memorial plaque at the crematorium