The Knock Out rose is revered for its disease and pest resistance, ease of culture and ability to produce high numbers of flowers practically year round in the warm climates across Florida. There are seven different rose selections that can be called a "Knock Out." Providing a fertile, well-draining soil and ample sunlight ensures success, and performing annual early spring pruning and a good fertilizer regime in Florida's sandy soils increases the health, vigor and floral display beauty of all Knock Out roses.
Provide roses with a sunny exposure in your garden. A minimum of six hours of direct sunlight is required for strong leafy growth and prolific, even flowering. Dappled sunlight in the hottest parts of the summer afternoon is acceptable, especially in the interior and southern half of the Florida peninsula.
Situate roses in a soil that is fertile but has good drainage. The soil pH is best in the range of 6.0 to 6.5, slightly acidic, however Knock Out roses are adaptable to neutral (7.0) to slightly alkaline soils (to 7.5) if organic matter and mulch is used as a soil topdressing.
Water roses as needed to keep the soil evenly moist, but never soggy or waterlogged. Watering in the morning is ideal; avoiding getting foliage wet if possible. This permits the plant to dry out over the course of the day and diminishes chances of fungal or other rot when the plant is wet after sundown. Knock Out roses in general are resilient to mildew and leaf spot, but proper watering is still a sound practice.
Pruning Roses in Florida
Trim back tall or lanky stems of the rose any time of year with hand pruners. Wear gloves when working on the rose bush to prevent prickling by the stem thorns.
Cut off damaged, dead, or diseased stems and leaves anytime of year as needed, making the pruning cut 1/4 inch above a leaf or bud on stems that are alive or free of disease. Rinse the pruner blades with rubbing alcohol after cutting at diseased plant parts to avoid spreading the disease with subsequent pruning of other stems or plants.
Conduct an early spring heavy pruning each year or every second year. Although not necessary on Knock Out roses, some selections can get quite tall, and the heavy pruning allows the gardener to shape the plant and force regrowth that is lush and invigorated, resulting in an increase of flowers.
Cut back main stems one-third to one-fourth of their original height, making the pruning cut 1/4 inch above a stem bud that is facing outward from the center of the bush.
Trim off any horizontal and small twigs, those thinner than a pencil. Make the cut nearly flush with the main stem, about 1/8 inch above it. Rinse pruning blades with the alcohol occasionally, but definitely between moving to another rose plant.
Fertilizing Roses in Florida
Apply a generous amount of compost to the area around the rose base each spring, keeping it away from the trunk of the plant. A 1 to 2-inch broken layer is ideal, scattered above the existing mulch.
Sprinkle additional organic mulch around the base of the rose, too, as needed, to maintain a consistent 2 to 3-inch layer. Keep the mulch 3 to 4 inches away from the trunk of the rose plant. Do this any time of year.
Scatter an all-purpose granular fertilizer around the base of the rose bush at a dosage recommended on the product label. This product should be a slow-release formula containing micronutrients. Apply this fertilizer three times per year: in early spring, in early summer, at the start of the rainy season, and again in early autumn.
Broadcast one cup of Epsom salts, a source of magnesium, any time of year around the base of the rose. Since much of Florida's soils are fast-draining sands, Epsom salt applications prevent yellow leaves and are particularly well-timed in early spring, early summer at the start of the rainy season, and again in autumn.
Water in the fertilizer applications, if desired, to wash the granules or compost into the mulch and down to the soil. Otherwise, allow natural rainfall or the timed irrigation watering to jostle particles downward. Don't worry, as long as water drips downward, the nutrients will make it to the rose roots.
About this Author
James Burghardt has written for The Public Garden, Docent Educator, numerous non-profit newsletters and for Learn2Grow.com's comprehensive plant database. He holds a Master's degree in Public Horticulture from the University of Delaware and studied horticulture and biology in Australia at Murdoch University and the University of Melbourne's Burnley College.