In most cases, plants in an urban planter box need watering more often than plants in a regular garden bed. A planter box holds a limited volume of soil, is exposed to air on multiple sides, and often dries out quickly because of sun, wind, reflected heat, and the urban heat island effect. A regular garden bed has a much larger soil reservoir, so it usually holds moisture longer and can go longer between waterings.
For urban planter box watering, check the soil every day or every other day during warm weather. In summer, many city planter boxes need water every one to two days, and small boxes in full sun or windy spots may need water daily or even twice a day during heat waves. In spring and fall, watering may drop to every two to four days. In winter, water only when the soil is dry, perhaps every one to two weeks, and less often if plants are dormant. For container plant watering, never rely on a fixed schedule alone. Push a finger about 2–3 inches into the soil; if it feels dry, water thoroughly until it drains.
Garden bed watering is different. Because the soil volume is larger, a regular garden bed can often be watered deeply once or twice a week in summer. In spring and fall, once every seven to ten days may be enough, depending on rainfall, soil type, and plant size. Water deeply and less frequently to encourage deeper roots. In winter, garden beds usually need little or no extra water unless they are under cover or in a very mild climate.
The exact watering frequency in city gardening depends on plant type, soil mix, pot size, mulch, sun exposure, wind, and whether the planter has a self-watering reservoir. To reduce work, add mulch, group plants with similar water needs, use drip irrigation, and consider self-watering planters. Always check soil moisture before watering. Overwatering can be as harmful as underwatering, especially in containers with poor drainage.