So it may be that when hyssop that was used to lift the sponge of sour wine to the lips of Lord Jesus, the only reason hyssop was mentioned was because that was what used. Both Matthew and Mark simply tell us it was a reed. That is, just the stalk of some sturdy plant.
But hyssop was mentioned several times in the Old Testament Scriptures: During the original Passover, the Israelites were instructed to use hyssop to apply the blood of a lamb or goat to the mantle of their houses so "the Lord would pass over the door and not allow the destroyer to enter your houses. (Ex 12:23) Hyssop was also used as one of the ingredients in a cleansing ritual for one who was healed of leprosy. And then we read in David's Psalm 51 Purge me with hyssop and I shall be whiter than snow.
There's one more time that hyssop is mentioned. In I Kings, Solomon's great wisdom is described: He spoke of the trees, from the (majestic) cedars that grow in Lebanon, to the (common and small) hyssop that grows in the walls.
Hyssop is only about 18 inches tall. Apparently that's all the lift that was needed to reach the One who was lifted up on the cross.
So for me, hyssop speaks of how close Jesus was to us when He paid our ransom: Not high in the heavens, nor below the depths of the sea; but He was right here among us.