Perhaps more important than having the plants is knowing what and where they are.
Making sure all the information about a plant is available and accessible is a vital part of holding a National Plant Collection.
All National Plant Collections need to provide an accessioned plant lists. This is a list of the plants in your collection, detailing (as a minimum) full scientific name, accession number, date of acquisition and source.
An accession number is a unique identifying number, or code, which can be used to track it through your collection. Information about the plant can then be attached to the accession, such as legal paperwork, pictures, characterisation data or plant health issues.
A purely numeric system can suffice (0001 and so on), although this does not immediately convey much information unless you are familiar with the plants concerned. So quite often this number is combined with the year of acquisition (2019-0001 and so on). At the very least this immediately tells you when you received the plant, so giving an indication of its age and longevity in your collection.
For a more in depth look at different ways of accessioning plants in a collection, see this document.
An accession policy describes how you decide which plants to add to your collection, and which plants you don't. It is determined by the collection category and scope. An example of an accession policy for a collection of Heuchera cvs. (1990-2010) would be: ‘to obtain all cultivars bred between the stated years, commencing with those originating in the UK, then those in the USA’.
It can be used to indicate current priorities or future direction: ‘to obtain all cultivars bred between the stated years, and once complete to look at the practicality of adding 1980-1990 to the collection’.
The accession number will link the plant to its source. It is important to keep information about the source as this can prove that you have the plant legally (in the case of species sourced either directly or indirectly from the wild). You may have examples of the same taxa from multiple sources and it is important have this recorded. Should there turn out to be a problem with one of the plants (such as being misnamed or a pest and disease issue), you will know which source it came from.
The accession number should appear on the labels for the plants. We recommend double labeling for all plant collections - one where you can read it and one sunk into the pot or buried underground, should the first one come off, fade or be rearranged by helpful children.
Some collection holders are using Near Field Communications tags, which can be read by a smartphone, to digitally label their plants. More details in this article on the collection holder's blog.
Other useful links to label suppliers, from plastic tags to botanic garden style engraved plaques are below: