Linda Benedict | 8/25/2008 11:15:32 PM
Plant response to increasing fertilizer rates: When plants were not fertilized, nitrogen deficiency and poor growth were observed in all species except daylily. When fertilized, all species, except daylily, responded positively to increasing fertilizer rates, and four pounds of nitrogen per 1,000 square feet produced in largest plants. However, because large-size plants often lack compactness and require more pruning, they received quality ratings lower than plants that were in lush growth but also were compact and had better flower display.
Comparison of fertilizer types: Better plant quality was observed in cigar plant, lantana and Mexican heather when two tablets per plant or two pounds of nitrogen per 1,000 square feet were used. These two treatments also resulted in better flower display in purple coneflower and black-eyed Susan. The high fertilizer rate – four pounds of nitrogen per 1,000 square feet – produced more flowers, but plant quality ratings were lower because of their large size and lack of compactness. As a result, applying two tablets per plant or two pounds of nitrogen per 1,000 square feet resulted in optimum quality of most plants in May (Table 1). When compared with two pounds of nitrogen per 1,000 square feet, two tablets per plant provided similar season-long nutrients with reduced total fertilizer use.
Overwinter survival rate: Daylily and lantana plants overwintered well regardless of fertilizer regimes. These plants need only minimum fertilizer to establish. Two tablets per plant resulted in higher survival rate (75 percent) in black-eyed Susan, cigar plant and Mexican heather. A single application of two tablets in guara produced results similar to a split application of one tablet at planting plus one pound of nitrogen per 1,000 square feet in July.
Based on these results, we recommend two tablets (0.26 ounce each) per plant at planting to establish most medium- to large-size herbaceous perennials such as lantana, black-eyed Susan, Mexican heather and purple coneflower. The LSU AgCenter recommends a low fertilizer rate at one pound of nitrogen per 1,000 square feet for daylilies.
Yan Chen, Assistant Professor, and Regina P. Bracy, Professor, Hammond Research Station, Hammond, La.
(This article was published in the summer 2008 issue of Louisiana Agriculture.)