Not only plants, but other things can communicate with us too. Circumstances can tell you that you have failed. Your body can tell you that your prayer didn't work - the Lord didn't heal you, etc. You need to follow Jesus' example and answer these things with a positive statement of your faith.
What good could it do to talk to a tree or an inanimate object? God created the heavens, the earth, and everything that's in the earth, by His words (Hebrews 11:3). The whole creation was made by and responds to words. Our words, when spoken in faith, release either life or death (Proverbs 18:21). They also affect people, things, and circumstances. We can release the power that's in faith by our words.
Speaking God's Word in faith brings the Holy Spirit into action. In Luke 4, when Jesus was tempted of the devil for forty days, it was the Word of God that Jesus used to defeat the enemy at His temptation. We must take advantage of God's Word by placing it in our hearts so that the Holy Spirit may bring it to pass at the right time to accomplish a complete and total victory.