The rimmon is the pomegranate (Punica granatum). It has beautiful red flowers which ripen to form edible fruit in late summer and early autumn.
 
The rimmon was one of the special seven varieties of the land, as described in Deuteronomy 8:8: "For the Lord your God is bringing you into a good land - a land with streams and pools of water, with springs flowing in the valleys and hills; a land with wheat and barley, vines and fig trees, rimmonim [pomegranates], olive oil and honey".

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A young pomegranate in Turkey. PICTURE: Georges Jansoone (licensed under CC BY-SA 3.0)

Rimmon fruit was brought back by the 12 spies who initially entered Canaan.

“They went up through the Negev and came to Hebron, where Ahiman, Sheshai and Talmai, the descendants of Anak, lived. (Hebron had been built seven years before Zoan in Egypt.) When they reached the Valley of Eshcol, they cut off a branch bearing a single cluster of grapes. Two of them carried it on a pole between them, along with some rimmon [pomegranates] and figs." - Numbers 13:22-23 

Rimmon were a sign of blessing as seen in Haggai 2:19: "Is there yet any seed left in the barn? Until now, the vine and the fig tree, the rimmon [pomegranate] and the olive tree have not borne fruit. 'From this day on I will bless you'."

Rimmon were used as a decoration on the high priest’s garments. They were to decorate the hem of his ephod, along with golden bells (Exodus 39:26). They also decorated the top of the bronze pillars in the Temple (Jeremiah 52:23).

Both the fruit and flower of the rimmon was referred to as a symbol of beauty. This is expressed in Song of Solomon: 

"Your lips are like a scarlet ribbon; your mouth is lovely. Your temples behind your veil are like the halves of a rimmon [pomegranate]."
- Song of Solomon 4:3 and 13

"Your limbs or cheeks are an orchard of rimmon (pomegranates)
Let us go early to the vineyards
to see if the vines have budded,
if their blossoms have opened,
and if the rimmon [pomegranates] are in bloom -
there I will give you my love.
The mandrakes [dudai] send out their fragrance,
and at our door is every delicacy,
both new and old,
that I have stored up for you, my lover."
 - Song of Solomon 7:12-13

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Opened pomegranate fruit. PICTURE: Fir0002/Flagstaffotos (licensed under CC BY-NC 3.0)

Nectar was taken from the rimmon and was used as a drink. Again, this can be found in Song of Solomon:
"If only you were to me like a brother,
who was nursed at my mother’s breasts!
Then, if I found you outside,
I would kiss you,
and no one would despise me.
I would lead you
and bring you to my mother’s house - 
she who has taught me.
I would give you spiced wine to drink,
the nectar of my rimmon [pomegranates]."
- Song of Solomon 8:1-2

Saul sat under a rimmon tree while awaiting Jonathon's return from fighting the Philistines in I Samuel 14: 2 while Joel mentions a time when the rimmon and many other trees are dried up. He uses this as a call to repentance:
“Despair, you farmers,
wail, you vine growers;
grieve for the wheat and the barley,
because the harvest of the field is destroyed.
The vine is dried up
and the fig tree is withered;
the rimmon [pomegranate], the palm and the apple tree -
all the trees of the field - are dried up.
Surely the joy of mankind
is withered away.
Put on sackcloth, O priests, and mourn;
wail, you who minister before the altar.
Come, spend the night in sackcloth,
you who minister before my God;
for the grain offerings and drink offerings
are withheld from the house of your God.
Declare a holy fast;
call a sacred assembly."
- Joel 1:11-14

This is an edited excerpt from Alvin Johnson's iBook 'Biblical Flora', 2017. The book is available for free download on iTunes. A teacher's edition is also available for purchase.