Some rosarians do not use mulch, as they maintain that mulch harbors disease and insects.? However, keeping unmulched beds free of weeds requires constant care. Some people feel that without mulch, there is less incident of crown gall and that fertilizer may be more easily worked into the soil.
Mulching is a convenient way to control weeds, insulate the soil against summer heat, and conserve moisture by slowing down evaporation. The humus resulting from the mulches make the nutrients already found in the soil more readily available to the roots of the roses. Soil temperature and moisture are consistent, providing favorable conditions for a continuous growth of fine roses.
The best time to mulch is after the soil has warmed and before the bushes start growing. Before you mulch, the soil should be soaked by a good rain or water from the garden hose. It has been found that a depth of four inches is necessary for most mulches to give the desired results. Cost and availability also determine which mulch to use. So that grass and weeds can be removed by hand, mulch should be placed no closer than six inches to the plant.
If weeds are out of control by the end of the growing season, and you did not use mulch, there is help. Casoron, a pre-emergent winter herbicide, is applied after there have been two killing frosts (temperatures below freezing). It comes in two strengths-4G and 10G. It should be applied one foot away from any plant that is only one year old. Casoron does not kill wild onions or Johnson grass. These must be removed by hand.
There are many materials for and methods of fertilizing roses. The best method is a matter of opinion, but a group of English researchers found that a combination of organic and chemical fertilizers will grow better roses than either one alone.
When you buy fertilizer, three numbers are printed on the bag or container. The first number indicates the percentage, by weight, of nitrogen included. The second number gives the percentage of phosphorus available as phosphoric acid or phosphorus pentoxide. The third number is the percent of potassium or soluble potash (usually potassium oxide). A soil analysis will tell you what formulation of fertilizer will be best.
For newly planted roses, add fertilizer only after the first blooming cycle and therafter only once a month. Stop feeding your roses by six weeks before the last bloom cycle. Scatter the fertilizer evenly around the bush, at least six inches from the base. Scratch it lightly into the soil, then water it in. If your soil is dry, water the ground soil the day before you feed your roses. On two-year-old or established bushes, feeding should occur in the spring, about four to six weeks before the first cycle of blooms, with continued feeding as discussed above.