The Smart Watering option is ideal for things like grass, trees, bushes, and flowers as their root structure is relatively stable over time. 

However, a vegetable garden changes dramatically and quickly over time as your vegetables grow. The root structure and leaf area index (used to calculate evapotranspiration) both change quickly for vegetables relative to other crops.

It’s for these reason we do not recommend using the Smart Watering option for vegetable garden zones.  We recommend turning Smart Watering off for those zone, selecting the watering time manually, and adjusting that time as your garden matures.