Established Rosebushes
Plants should be well mulched with blends of organic materials such as compost, wood shavings and aged manure (chicken and turkey are best, but steer will do). Mulch is not only nutritious on its own, it provides the perfect medium over which concentrated fertilizers should be applied.
Suggested feeding schedule is for modern roses only – those that repeat their bloom.
March/April
Apply Chelated Iron in early Spring
1st week – Apply One of the following water-soluble fertilizer concentrated in nitrogen along drip line:
31-0-0 ( slow-release formula)
33.5-0-0 (ammonium nitrate),
21-0- 0 (ammonium sulfate)
15.5-0-0 (calcium nitrate).
3rd week – Apply 2/3 cup Epsom Salts (Magnesium Sulfate) per bush
Epsom salts (magnesium sulfate) are activators for plant enzymes essential to the growth process.
May/June
1st week apply granular, water-soluble, balanced fertilizers – 10-10-10 or 20-20-20 fertilizer
3rd week apply ½ cup Epsom Salts (Magnesium Sulfate) per bush
July/August
1st week apply granular, water-soluble 20-20-20 fertilizer
3rd week apply fish emulsion- 1 teaspoon per gallon. RATE: 2 gals per bush
September/October
1st week apply granular, water-soluble 0-10-10 fertilizer
3rd week apply fish emulsion- 1 teaspoon per gallon. RATE: 2 gals per bush
Don’t apply anything after Halloween.
Summarized from an Article by Rose authority: Rayford Reddell, owner of Garden Valley Ranch Nursery Petaluma CA., Article 2003, San Francisco Chronicle
Read full article here: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2003/03/22/HO47251.DTL#ixzz1Eeodxsnm