Blending is not a brewing method
It is worth separating clearly. Brewing methods describe what you do with water: infuse, decoct, steep cold. Blending describes what goes into the vessel before that, and a blend is brewed by whichever method its heaviest component requires. This is why blending is documented here rather than as a brewing method in the catalogue.
The extraction problem
The real difficulty in blending is that plant parts release at very different rates. Flowers and delicate leaves give up most of what they have in three to five minutes; roots, barks and seeds need fifteen or twenty minutes of simmering. Put chamomile flowers and liquorice root in the same pot for the same duration and one is over-extracted while the other has barely started. The conventional solutions are to simmer the dense material first and add the delicate material at the end, to break the dense material more finely to speed it up, or to accept the compromise and blend within a single plant-part family.
Balance and proportion
A few components dominate a blend almost regardless of proportion. Liquorice is intensely sweet and will lead at very small percentages; lavender, clove and star anise are similarly assertive; peppermint tends to take over anything it is put with. Mild bases — rooibos, chamomile, lemongrass, honeybush — carry a blend without competing. The usual working approach is a base of 60 to 80 per cent, a supporting middle, and an accent at a few per cent, adjusted by tasting rather than by formula.
What TeaHQ will and will not do with blends
Blends will be recorded for what they are and how they are prepared. TeaHQ will not construct or recommend blends for a stated purpose — an 'evening blend' or a 'digestion blend' is a functional claim assembled from several plants, and the evidence problem it creates is larger than the sum of the individual ones. If those are ever published they will need sourced evidence for the combination, not merely for its parts.