How to Fertilize Bearded Iris
- 1). Apply 1 to 2 lbs. of a general-purpose 5-10-10 fertilizer per every 100 square feet of iris bed prior to planting. Work the fertilizer into the top 6 to 8 inches of soil one week before planting.
- 2). Fertilize once the flowers open the first summer after planting with 1 lb. of 5-10-10 fertilizer per every 100 square feet. Work the fertilizer into the top 3 to 4 inches of soil around the perimeter of the plant, taking care not to get fertilizer in contact with the roots or foliage.
- 3). Water the iris thoroughly after fertilizing, moistening the top 6 inches of soil. Immediate irrigation washes the fertilizer down into the root zone of the iris.
- 4). Feed established iris once a year, either in spring when new growth begins or in summer after the plants bloom. Apply 1 lb. of 5-10-10 fertilizer per every 100 square feet, taking care to keep the fertilizer off the plant's roots.
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