How to Fertilize Sunflowers in Containers
- 1). Amend container soil at planting time and once or twice a year thereafter with a light 1- to 2-inch top-dressing to boost basic soil fertility. Use bat guano, compost, leaf mold or well-rotted manure, or some combination thereof, to bring the soil closer to the quality of nutrient-rich ground soil.
- 2). Apply a gentle, low-nitrogen fertilizer to the potted sunflowers using a product with a guaranteed analysis of 5-10-10 but no higher. Apply during the growing season according to the product label directions for use on container-grown plants. Alternatively, cut the ground-recommended application rate by 50 percent to prevent overdosing the plant. Always err on the side of less fertilizer for sunflowers, as any excess may hurt flower production and quality.
- 3). Water your sunflower generously after applying any top-dressing or fertilizer products. Add enough water to soak the soil in the container thoroughly, continuing until you see a small amount of excess water drain out of the container. Never let the soil dry out; aim for evenly moist soil at all times.
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