Rare flowers activate their debuff ability which also counts towards their evolution progress. You can alternate between standing on a campfire and eating rare flowers to evolve them. The wifi symbol on the right is the bebuff cool down and the numbers that show up at the bottom show you the health buffer threshold for the health regen ability. So if you set the threshold to 50 you'll need to take 50 damage to activate the ability. But you'll need to take the damage quickly to reach the threshold. The actual amount of health you have doesn't matter. Once the ability activates the numbers at the bottom will change colors and start to countdown before you can activate the ability again. The number of times you need to activate one of the abilities to get a growth surge seems to change as you progress