Increasing Production of New Roots by Potted Roses with Root Applied IBA

Dormant bare root rose (Rosa × hybrida ‘Las Vegas’) plants with roots dipped in a 500 ppm solution of indole-3-butyric acid (IBA) produced 50% more new roots than untreated plants. However, plants treated with 100 and 500 ppm IBA had fewer open flower buds 8 wks after potting and shorter average shoot length after 18 wks than did controls. Treatment with the potassium salt of IBA (KIBA) at 100 and 500 ppm also stimulated new root production and retarded flower bud development but did not reduce shoot length. Addition of starch-polyacrylate gel to treatment solutions counteracted the root promoting effect of IBA but not of KIBA. Gel itself also caused a reduction in average shoot length.