Spare ground, tucked away from sight, is how most allotments started. They often do not have a proper postal address. You could get there but could an ambulance find its way?
When someone became seriously ill on an Edinburgh site, the ambulance was called, with the location given simply as the name of the allotment site and the name of the road the entrance was on. The ambulance spent over half an hour trying to find the site entrance to help the sick person.
To prevent this happening again the Federation of Edinburgh Allotments decided to coordinate with the emergency services. It produced a list of every site in the city giving

site name, nearest postcode, OS 10 digit grid reference

any other special local useful information to help find the site

This list has been well received and Edinburgh’s plotholders can feel a little safer. Is this something your organisation could do? 

The 'What 3 words' app is now widely used by emergency services. It uses 3 words to pinpoint specific locations. To find the 3 words that match your site, simply visit the site here and use the search function to find your site on the map. Once you have your three words, don't forget to display them somewhere prominent on the site.