As explained in the July edition of the Cornell Cooperative Extension’s Gardening Gazette, many types of roses have just completed a major flush of bloom and could use some supplementary nourishment now. Frequent fertilization (every four to six weeks) from early spring to late July is desired by roses. However, an early July feeding is probably the most needed because so much of the food stored in these plants was used up to produce the recent floral display.
Since Hybrid Tea and Grandiflora bushes and climbers, as well as Floribunda roses, bloom on new growth, a fertilizer application now will stimulate growth and bud development for more flowers later this year. With most climbing roses that flower on older wood, this shot-in-the-arm will stimulate growth for better bloom this year.
For a bed of roses, apply two to three pounds of a complete fertilizer, (ex.: 5-10-5 or 5-10-10) for 100 square feet or about two tablespoons per plant. Spread the fertilizer evenly underneath, but several inches away from the crown. Water-in thoroughly so the fertilizer gets below the surface layer of mulch and into the root zone.