Roses are especially susceptible to diseases, particularly powdery mildew and black spot. These are the most severe where humidity or rainfall is high, or where air circulation is poor. Well-maintained plants are less likely to succumb to diseases than weak ones. Follow the recommendations given in our past blog posts for planting, watering and fertilizing, and pruning your roses.
Pruning is the science of removing growth to achieve one or more goals: keeping the plant healthy, making it more productive, controlling its size, or encouraging it to grow in a particular shape or direction. Pruning stimulates new growth, an important factor in flowering because many varieties of roses produce flowers only on new canes.
Watering: Under normal conditions, roses need an inch of water a week. Sandy soil dries out more quickly than a clay or loam and thus needs more frequent watering, perhaps every 5 days instead of once a week. Adding organic matter, such as Leaf Gro, to a sandy soil can help it hold moisture so that watering is not needed as frequently. It is important to water deeply (12 to 18 inches) but as infrequently as possible to encourage deep roots. Roses with deep roots will be stronger, healthier, and more drought resistant than those with shallow roots. Water early in the day so that the leaves do not stay wet throughout the night, as this fosters disease, especially if you are using an overhead watering system rather than a drip system.
Container grown roses, like the ones sold at Johnson’s, can be planted anytime from early spring through mid-fall. As with all plantings, choose a day that is not windy, and if possible, plant late in the afternoon or on a cloudy day. This lessens transplanting shock, as planting in full sun can cause foliage to wilt. Roses like rich, fertile, moist, but well-drained soil. They also need good air circulation, ample growing room, and protection from harsh elements. Locate your roses where they will not compete with other plants for food and water.