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Illinois bundleflower [Desmanthus illinoensis (Mich.) MacMill] is a warm‐season perennial legume native to the central USA. Little is known about its forage quality in the upper midwestern USA. Two experiments were established at four Minnesota locations in 2000 to evaluate the effects of N fertilization, maturity at harvest, and residual height of cutting on the acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), in vitro true digestibility (IVTD), in vitro dry matter digestibility (IVDMD), and leaf proportion of three Illinois bundleflower (IBF) ecotypes. Whole‐herbage forage quality was greatest (P < 0.05) at early flower in mid‐July with average ADF, NDF, and CP concentrations of 315, 352, and 180 g kg−1, respectively. Fiber values increased to 412 and 479 g kg−1, respectively, while CP decreased to 129 g kg−1 at late pod in mid‐August. Leaf proportion decreased (P < 0.05) from 618 g kg−1 at early flower to 335 g kg−1 at late pod while leaf CP decreased (P < 0.05) from 216 to 147 g kg−1. Whole‐herbage IVDMD and IVTD concentrations decreased (P < 0.05) from 470 and 648 g kg−1 at early flower to 390 and 560 g kg−1 at late pod, respectively. Increasing residual cutting height from 15 to 35 cm decreased (P < 0.05) ADF and NDF concentrations by an average of 50 g kg−1 and increased (P < 0.05) IVTD, IVDMD, and CP concentrations by 43, 39, and 20 g kg−1, respectively. Illinois bundleflower can provide good quality summer forage in the upper midwestern USA, but more research is needed to ascertain the implications of its low IVDMD on animal performance.

Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMillan] is a warm‐season perennial legume native to the central plains of the USA with potential as both a forage and grain crop. The effects of management variables on Illinois bundleflower (IBF) forage production in the upper midwestern USA have not been evaluated. We evaluated the effects of maturity at harvest, cutting height, and N fertilization on forage yield, regrowth, and persistence of three northern ecotypes of IBF. Field experiments were established at four Minnesota locations in 2000. Total‐season forage yields in postestablishment years ranged from 2.5 to 5.3 Mg dry matter (DM) ha−1 across environments. First‐harvest forage yield increased (P < 0.05) from 2.8 Mg DM ha−1 at early flower in mid‐July to 4.2 Mg DM ha−1 at late pod in mid‐August. In mid‐September, within‐season regrowth averaged 1.7 Mg ha−1 from plants previously cut at early flower and 0.6 Mg ha−1 from plants cut at late pod. A 35‐cm cutting height resulted in 60% more regrowth yield (P < 0.05) than a 15‐cm cutting height, but only in plants harvested at early flower. Plants cut at late pod in 2001 did not persist into 2002. October root total nonstructural carbohydrate (TNC) concentration ranged (P < 0.05) from 244 g kg−1 in plants cut at late pod to 280 g kg−1 in plants left uncut. Complete winterkill of all treatments at all locations between 2002 and 2003, regardless of October TNC level, may have been caused by below‐average snow cover. Illinois bundleflower can provide summer forage in the upper midwestern USA, but persistence in monoculture is limited, especially in harsh winters.

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