Yes, drainage holes are absolutely essential for urban planter boxes. Without them, excess water has no way to escape, leading to waterlogged soil. This condition suffocates plant roots by depriving them of oxygen, creates an environment for root rot to develop, and can ultimately kill your plants. It's a fundamental rule of container gardening, whether on a balcony, rooftop, or patio.
So, how many drainage holes are ideal? There isn't a single universal number, as it depends on the planter's size. A good rule of thumb is to have at least one hole for smaller planters (under 24 inches in length or diameter). For larger containers, you should have several holes spaced approximately 6 to 12 inches apart. The key goal is to ensure water can drain freely from the entire base of the planter, preventing any area from becoming a stagnant pool.
If your decorative pot lacks holes, you have options. The best practice is to use it as a "cachepot." Simply plant in a plain, plastic nursery pot that has sufficient drainage and then place that pot inside the decorative one. Remember to empty the outer pot of any accumulated water after watering. Alternatively, you can carefully drill holes into the base of many materials like plastic, wood, or fiberglass. For successful urban gardening, prioritizing proper drainage is the most important step you can take for vibrant and healthy plants.