Using chemical fertilizers too early can burn new or recently dormant rose roots. Wait until after your roses’ very first bloom, and after you prune them in the early spring and see new growth, to use chemical fertilizer. This first fertilization is sufficient for most species types of roses. The numbers on fertilizers stand for Nitrogen-Phosphorus-Potassium content. General-use fertilizers have a balance of the 3 nutrients, and come in 10-10-10, or 12-12-12, which is a bit stronger. Either is fine to use for most rose types. For granular fertilizers, work this amount of fertilizer into the top 2 inches (5.1 cm) of soil surrounding your bush with a cultivator. Then water your rose thoroughly.  Liquid chemical fertilizers have different amount specifications for each dose, so read the instructions carefully before applying them. Remember to only apply chemical fertilizers after the plant is well-established in the spring. Always read the instructions for the correct amount of fertilizer before applying it. Some specialty roses, like hybrid teas or floribundas, benefit from a second fertilization in mid-summer. This helps them to stay healthy through the remaining summer months. Apply 4–8 oz (110–230 g) of granular fertilizer in a band around the base of your bush. Still other roses are known to be repeat-bloomers, and benefit from a third and final fertilizing in mid-July. This can also be beneficial if you have a particularly long growing season, or plants continue blooming through October and November. Follow the same procedures for this application as you did for the first 2 in early spring and mid-summer. If you’d rather do 1 chemical fertilizer application and be done with it for the year, try getting a timed-release fertilizer. These capsule fertilizers release their nutrients throughout the season in either 4, 6, or 8 months.  Generally these fertilizers use about 4 oz (110 g) per plant and are applied in May, but read the instructions carefully before using them Write the dates you apply fertilizer on a calendar to avoid over or underfeeding your roses. If you apply fertilizers too late in the growing season, you could get young, soft growth that’s easily damaged by the first frost. To encourage your roses to begin preparing for dormancy, stop fertilizing them 35-40 days, or 6-8 weeks, before the first frost. In many areas, this will be around mid-August. Use the first frost prediction for your exact region to be sure.
Wait to use chemical fertilizers until plants are well-established in the spring. Choose a general-purpose fertilizer of 10-10-10 or 12-12-12. Spread 4–8 oz (110–230 g) solid fertilizer in a band 6 in (15 cm) from the plant. Reapply a chemical fertilizer once in mid-June for specialty roses. Do a third application for repeat-blooming roses in mid-July. Try a timed-release fertilizer instead of doing multiple applications. Stop all fertilization 35-40 days before the first frost date.