For the third day, I will discuss some of the symbols and attributes of the Goddess.
As Queen of the Gods, Hera will always be shown with the regalia associated with the office. Therefore she is often depicted holding a sceptre or staff, sometimes lotus-tipped as in the image to the side of this text. Besides the sceptre, she also wears a diadem (πόλος) or crown (στέφανος), sometimes obscured by a headscarf or veil. The veil indicates her married status and is a symbol of modesty, thus relating to her domain of Marriage and married women. Going back to her royal status she is often depicted seated upon a throne.
When it comes to animals and plants, the peacock (τάως) is by far her most commonly associated animal. Indeed, she has a special relationship with this favourite bird of hers. For when Zeus desired Io, a priestess of Hera, Hera almost caught them. Zeus managed to shapeshift Io in the nick of time, giving her the shape of a white cow. Zeus swore he had not seen Io or had pursued her in any way. Hera was still suspicious, however, and demanded the cow as a gift. Zeus had no other option than to oblige her. Hera then locked the cow into a cave and had the cave entrance guarded by Argos Panoptes, a hundred-eyed giant who never fully sleeps, as he always has a few eyes open. When Zeus wished to lay with Io, however, he sent his most wily son, Hermes, to get rid of Argos. Hermes tricked Argos by playing a tune for him on the flute, and one by one all Argos’s eyes fell asleep. When finally Argos’ last eye closed and he was fast asleep, Hermes slew him, for which he is named Argeiphontes, the Slayer of Argos. Hera discovered this, however, and sent a gadfly after Io, who was still a cow at this point. Then, to honour Argos who had loyally guarded the cow Io but had fallen to Hermes’ trickery, she took the giant’s one hundred eyes and placed them on the tail of her favourite bird, thus giving the peacock their splendid display of a tail.
Another sacred animal of Hera’s is the cuckoo (κόκκυξ), as Zeus took that form to seduce her in their youth. The cow also is a sacred animal of Hera and she is named Cow-eyed Hera by Homeros. This connection with cows is certainly interesting given the above-cited myth of Io being turned into a cow. Likely there is some mythic symbolism at play there, but I do not know exactly what it might mean, or how it could be interpreted.
Hera also has some sacred plants: the pomegranate (ῥόα), the willow (λύγος, Vitex Agnus-castus), and the lotus (λώτος). The first of these is due to the fact that the pomegranate is a round fruit, filled to the brim with seeds. In this, it resembles the male testicle, which is also round and full of seed. As Hera is the Goddess of Marriage, and the primary function of Marriage in ancient Hellas was to produce legitimate heirs, the pomegranate thus symbolises Her role in the production of heirs. The second one, the lygos-willow is due to the claim that when Rhea gave birth to Hera, either in Argos or Samos, she clutched a lygos-willow as Hera was being born. For this reason, the tree is sacred to her. And in Samos, the cult image of Hera would be ritually bound with branches of the lygos-willow at some festivals. The lotus, finally, is simply a beautiful and royal flower, befitting the Queen of the Gods.
These are the primary attributes of the Goddess Hera that I have been able to find.