Content reference: demo v0.5.4
Try the small movement fix
A developer reply on the original game page specifically recommends a little wiggle around the plant in this demo. Move across the planted area instead of waiting motionless. With mouse controls, click near the snail for movement and watering. Watch whether the plant responds before planting more ground.
Check water and reach
Look at your water supply and return to a pond if necessary. The v0.5.2 update added a hotbar tooltip when there is not enough water. Compare watering reach, water capacity and absorption upgrades with your current route: capacity helps the amount carried, while absorption and reach solve different obstacles. Read the live tooltip for the next effect and price.
Separate old bugs from this build
The v0.5.2 notes fixed an inability to paint in the second pond. If an old guide describes that bug, it is not a current rule. The developers also distinguish the demo’s movement-based watering from standing-still watering in the full game. If a patch remains dry, test water, position and a small movement before treating it as failed growth.