That's an excellent question! The number of plants you can fit in one of our standard urban planter boxes isn't a one-size-fits-all answer; it depends heavily on the mature size of the plants you choose. Overcrowding is the most common mistake, which leads to competition for water, nutrients, and light, resulting in weaker plants.
As a general rule, we recommend focusing on the plants' final spread. For most leafy herbs like basil, cilantro, or parsley, you can comfortably plant 3 to 4 per standard box (approximately 24 inches long). For larger vegetables like full-sized tomatoes or peppers, one plant per box is ideal to ensure it has enough room to flourish.
For a vibrant, mixed planter, consider the "thriller, filler, spiller" technique. Plant one tall, dramatic "thriller" (like dwarf kale) in the center, surround it with 2-3 bushy "fillers" (like marigolds or lettuce), and finish with 2-3 trailing "spillers" (like nasturtiums or creeping thyme) at the edges. This method maximizes visual impact and healthy growth without overcrowding.
Always check the plant tag for its specific spacing requirements—this is your best guide. When in doubt, it's better to underplant than overplant. You can always add more seasonal flowers later, but a thriving, less-dense garden will always outperform a crowded one.