COPPER-TREATED PLUG FLATS INFLUENCE ROOT-GROWTH AND FLOWERING OF BEDDING PLANTS

A copper hydroxide formulation (0%, 3.5%, 7%, 11% Cu) was applied to p lug trays before sowing seeds of Impatiens xhybrida L. 'Accent Red', P elargonium xhortorum Bailey 'Scarlet Elite', and Petunia xhybrida Hort . Vilm.-Andr. 'Ultra White' to investigate the influence of the formul ations on ease of transplant, root growth, and shoot growth. These fac tors also were investigated in Cu-treated seedling plugs held past opt imal transplanting stage. Root spiraling and seedling height at transp lant were reduced for all taxa grown in Cu-treated trays, regardless o f concentration, compared to seedlings from nontreated trays. Root wei ght and shoot weight responses to Cu treatments at transplant and at f lowering varied among taxa. Mature heights of all taxa were unaffected by Cu treatment; however, flowering date was delayed for impatiens an d geraniums transplanted at optimal time from Cu-treated trays. In gen eral, petunias displayed little response to Cu treatment. Root spirali ng was reduced and plugs were removed more easily from Cu-treated than from control trays stored for 2 weeks in the greenhouse, but flowerin g time was delayed for 12 days for impatiens and petunias and 21 days for geraniums, regardless of Cu concentration.