There Was No Man To Work - Genesis 2:5

Genesis 2:5 ESV 

When no bush of the field was yet in the land and no small plant of the field had yet sprung up—for the Lord God had not caused it to rain on the land, and there was no man to work the ground,

The life of God had not taken root on the earth. There was no need for the rain of heaven for there is no one to receive the rain from heaven, the blessings and light from heaven, the living water that would bring forth that light and life on earth. There was no seed in the ground and there was no man to work it if it was. 

Plants in these verses may signify those people who would be able to accept the seed of the word and drink the rain from heaven. The ground was void until that took place. It would take a man to make that happen. 

Revelation 9:3-4 ESV 

Then from the smoke came locusts on the earth, and they were given power like the power of scorpions of the earth. They were told not to harm the grass of the earth or any green plant or any tree, but only those people who do not have the seal of God on their foreheads.