Well yes Wilco but it's not very helpful is it??
...
Going by this Heather is blossom. Try negotiating your price on that basis....
PH
There is a bit more to it than that. I would aregue that if there are "two types of honey" permitted in regulation, it would be blossom honey (which "must" be labelled as honey, blossom honey or nectar honey) and honeydew honey (which "must" be labelled as honeydew honey) - thus the two are completely separated by the labelling regulation.
I suspect that the main reason that Heather honey is typically singled out within the honey/blossom honey/nectar honey category is that it alone has a different specified threshold for water content (being higher at 23%) than the other honeys in that category. Since water content is about the only "constituent property" readily available for small scale producers to measure, and since it is well understood that getting water content too high significantly increases the risk of fermentation within the expected shelf-life of the product, it is not surprising that it gets special treatment.
However Heather honey is not unique for specifying as a floral source (that's all that it is). The additional labelling requirements section, while it doesn't directly answer your initial question, is probably far more what you were looking for in that permits ("may") but does not mandate adding information "relating to its floral or vegetable origin", with the proviso that you can only do so if "the product comes wholly or mainly from the indicated source and possesses the organoleptic, physico-chemical and microscopic characteristics of the source". So you can call it "borrage honey" but only if it is "wholly or mainly" from borrage. In fact, the compositional criteria section ends up listing a very wide range of monofloral sources based on the varying sugar compositions that might be expected.
false acacia (Robinia pseudoacacia) honey, alfalfa (Medicago sativa) honey, Menzies Banksia (Banksia menziesii) honey, French honeysuckle (Hedysarum) honey, red gum (Eucalyptus camadulensis) honey, leatherwood (Eucryphia lucida, Eucryphia milliganii) honey, Citrus spp. honey, lavender (
Lavandula spp.) honey, borage (
Borago officinalis) honey, bell heather (
Erica) honey, chestnut honey, eucalyptus honey, lime (
Tilia spp.) honey, ling heather (
Calluna vulgaris) honey, manuka or jelly bush (
Leptospermum) honey, strawberry tree (
Arbutus unedo) honey and tea tree (
Melaleuca spp.) honey
(apologies if there are repetitions I've missed as that's a concatenation of several lists)
So to get to the core of the question, what are the requirements for "wholly or mainly". And that's where regulation largely ceases to answer the question.
For the specific categories noted above, there is at least one compositional requirement (such as fructose or glucose percentage in the sugars, or electrical conductivity) which you could arguably measure given suitable equipment. But that does not demonstrate that it is from such a source.
Beyond that, there are various "guidelines" around. The primary source for pollen analysis requirements appears to be Methods of Melissopalynology by J. Louveaux, A. Maurizio, G. Vorwohl whose techniques appear to be widely adopted for "unifloral" honeys - broadly speaking >45% of pollen from a "normally represented" plant is enough to be "predominantly" that floral source, can be as low as 20% for significantly under-represented pollens, and in the case of over-represented pollens could be as high as 90%. There are also considerations as to "what the rest is" (e.g. if you're at 45% but the other 55% are under-represented pollens, it probably isn't "predominantly" that plant - indeed it is possible for one honey sample to be "predominantly" more than one different source if common sense and care are not applied.
I would suggest that there is reasonable expectation of the keeper - if bees were taken to a specific single source (e.g. heather) where were no other sources of forage available to them, it is credible to claim that a correctly appearing (i.e. thixotropic) honey is heather honey. Conversely, if you happened to see a lime tree in bloom near a hive, and heard some bees on it, that might not be sufficiently compelling to say that a particular frame, box or tank of honey thence extracted is lime honey.
The fact that there is no clear delineation between the extremes for what should or should not be considered monofloral is not that helpful. If it's going to make a significant commercial difference it might be worth taking the time for the pollen frequency analysis in those cases, but it probably also depends on the scale, the market, and to some extent the expected likelihood of challenge...
For the record, Louveaux et al consider Tilia to be under represented, with an estimate of 20-30% pollen frequency (with the caveats above about what the rest is) expected in a predominantly Lime honey.