How often to water a vegetable garden in Oregon depends on the season, type of plant, and whether the plants are in the ground or in a pot: Season: In hot weather, established plants with deep roots may need watering every five to seven days. In extremely hot weather, you may need to water daily or every other day. Plant type: Shallow-rooted vegetables like cucumbers, spinach, and carrots may need more frequent watering, especially in hot weather or in light soil. Seedlings may also need more frequent watering, like twice a day until they're established. Location: Potted plants and newer plantings may need more frequent watering than established plants in the ground.