Keeping your urban planter boxes thriving requires knowing when your plants need extra nutrition. Unlike plants in the ground, container plants have limited soil and exhaust available nutrients more quickly. Here are the key indicators that it's time to fertilize.
The most common sign is slow or stunted growth. If your plants seem to have stopped growing or are producing smaller leaves than usual, they likely need a nutrient boost. Another clear signal is leaf discoloration. Yellowing leaves, particularly starting with the older, lower leaves, often indicate a nitrogen deficiency. Pale green or yellowish leaves with green veins can point to an iron deficiency.
Pay attention to flowering and fruiting as well. A lack of flowers, buds that drop off, or poor fruit development can mean your plants are hungry for phosphorus and potassium. Generally, a good rule is to fertilize most planter box plants every 2-4 weeks during their active growing season. Always water your plants thoroughly before applying fertilizer to prevent root burn. Using a balanced, water-soluble fertilizer designed for vegetables or flowers will typically give your urban garden the boost it needs to remain productive and beautiful throughout the season.