You should fertilize your garden depending on the type of plants, soil, and fertilizer used, but general guidelines are as follows:

• For vegetable gardens, apply granular fertilizer every 3 to 4 weeks during the growing season or use a water-soluble fertilizer weekly when watering

• Slow-release fertilizers can be applied about once per growing season, while quick-release fertilizers may be used monthly

• For indoor or container plants, fertilizing with liquid plant food once a month during spring, summer, and fall is typical

• Heavy-feeding plants may require more frequent fertilization, while some plants need little or no fertilizer

• Fertilizing should begin when plants start growing and continue through the growing season, including when fruits or vegetables appear, to maintain productivity

• Avoid fertilizing in winter or when plants are dormant, and do not over-fertilize as it can harm plants

• A practical rule for garden plants is fertilizing every third watering with water-soluble fertilizer, which could range from every few days to every few weeks depending on watering frequency and season

In summary, for most outdoor gardens, fertilizing every 3 to 4 weeks with granular fertilizer or weekly with water-soluble fertilizer during active growth is recommended. Adjust frequency based on plant type, soil quality, and fertilizer type to avoid over-fertilizing