This is what the National Trust for Scotland have to say:
The Trust has no formal policy which would cover all situations across the wide range of properties that we have responsibility for in Scotland. The Trust is respectful of peoples’ wishes but must have regard for a wide range of issues including the environmental impact on soils, plants, rivers and streams.
Broad guidelines are available to Trust Managers and any proposal or arrangement for the scattering of ashes or any associated ceremonies should be discussed and agreed with individual property managers beforehand. Contact details are available on the Trust’s website. If proposals are deemed acceptable, the advice given may include specific locations and appropriate times of day with regard for other planned events and consideration for other visitors.
For the avoidance of doubt there would be a presumption against the erection of any sort of memorial, however temporary.
This information was correct at the time of publication, organisations can change their position so for the most accurate information please contact the origination in question directly.