Impact of biostimulant and cultural factors on whorled mountainmint (Pycnanthemum verticillatum (Michx.) Pers. var. pilosum (Nutt.) Cooperr.): growth performance and assessment of arthropod visitation

Abstract

This study investigated the effect of a microbial biostimulant (Effective Microorganisms-1) on growth and flowering of a native forb (Pycnanthemum verticillatum (Michx.) Pers. var. pilosum (Nutt.) Cooperr. [Lamiaceae, whorled mountainmint]) grown under different irrigation and fertilizer levels and in presence or absence of organic soil amendment. Plant height, width, and number of main stems were unaffected, while the number of inflorescences were significantly higher in plants treated with the biostimulant. Plants exhibited slightly enhanced growth (plant width and number of main stems) under higher supplemental irrigation (3.81 cm [1.5 in] water per week as opposed to 2.54 cm [1 in] per week); however, plants had more inflorescences under lower supplemental irrigation. Plants grown in unamended soil were wider than plants grown in amended soil, but no other morphometrics were affected by that cultural factor. Whorled mountainmint attracted a diverse population made up of arthropods: pollinating (19+ families and 2 genera), beneficial (11+ families), and herbivorous (15+ families). Anthesis significantly augmented number of pollinating insects but it did not affect number of predatory and (or) other beneficial arthropods, nor plant-feeding arthropod taxa. Effective Microorganisms-1 biostimulant may be utilized to enhance establishment and flowering to further boost arthropod visitation and successfully grow whorled mountainmint with low inputs.