by John Hefner
NOTE: John Hefner, leader in the Indianapolis Rose Society, is one of the foremost authorities on growing and showing roses. Advice from him is advice that you can take to the garden and to the Rose Show table. Thank you John for sharing your considerable knowledge with us. He and his wife, Donna, are two of the most decorated rosarians in the American Rose Society. Their mix of rose growing knowledge and creativity is hard to beat!
– John Hefner
Roses need fertilizer for sustained growth and vigor.
When discussing fertilization, there are numerous programs depending on the desired results. It may be as simple as buying and using a fertilizer labeled “Rose Food” and follow directions on the package. It also can be a complicated program using many different types of various products involving chemical, organic, granular and water soluble formulations.
For any fertilization program to be effective, the rosarian must know…
- Garden’s soil type
- Quality of drainage
- And, the amount of humus in the rose beds
Fertilizer will not be effective if the pH is not correct. Roses need a pH of 5.8 – 6.5.
I would recommend a pH check during the growing season for desired results. The more chemical fertilizer that is used, the more the pH may vary. Note: pH meters are available at many garden centers locally and online.
Basic forms of fertilizer…
- Granular, which needs to be scratched into the soil.
- Powered which is designed to be dissolved in water for liquid feeding.
- Timed release is a pelletized form designed to release over time. This type is especially effective for use in container growing.
- Organic products are nutrients that occur by nature.
Nitrogen is the most needed element.
- Nitrogen stimulates growth and dark green healthy foliage.
- Some forms of nitrogen are fast acting, others are slower.
- The first number on a fertilizer label is the nitrogen content.
Phosphorus and Potassium – The second and third numbers in a fertilizer label.
- Both are needed to stimulate growth but since phosphorus moves very slowly through the soil it is recommended that when planting, it can be added to the planting hole. Super phosphate and bone meal are good sources of phosphorus.
Micronutrients needed for optimum growth are iron and magnesium.
- Iron can be added by applications of an iron supplement that is sold in numerous garden shops.
- Magnesium is recommended by the addition of Epson salts, which intensifies flower color and increased basal canes. Some fertilizers also have additional micro-nutrients in their formulations.
Feed often but don’t over fertilize. The general rules are little and often and error on the side of less is more. Fertilizers will not be effective and may burn roots if not watered in thoroughly. Always water before and after applying fertilizer.
Pick a Fertilization Plan – Since rose feeding is a personal thing you may want to choose from some of the following options.
Lazy and Cheap – Buy a timed release formulation and apply early in the spring at pruning time and again in the middle of summer and water well. This may provide for enough nutrients for the entire season, however, you may not have superior plants and blooms. Old Garden Roses and one time bloomers can benefit from this program.
Conventional Program – Apply a high nitrogen fertilizer at pruning time, urea 46% nitrogen or many lawn fertilizers will be effective. If using lawn fertilizers, make sure they do not contain weed killers in the formulation. Always water well after application as the high nitrogen content will burn roots. After growth is established to about 12 inches, apply a water soluble formulation 20-20-20 or similar rose formulas. Examples are Peters, Schultz, and Mills Easy Feed etc. Use one tablespoon per gallon and apply one-two gallons per plant for large roses and one-half the amount for miniatures and mini floras. One advantage of using water soluble fertilizers is that many contain trace elements essential for vigorous growth. At this time, the use of Epsom salts is desirable as it can be dissolved in water at the same rate of soluble fertilizer. Epson salts may also be used as a dry application and watered in well. One-half cup per plant spread around the base of the plant is desired.
After the soil has warmed, usually early to mid-May, an organic fertilizer can be applied. Organic fertilizers are ones that that occur naturally such as alfalfa, fish meal, blood meal, cottonseed meal, composted manure and others. Our rose society makes and sells a very effective organic fertilizer. Suggested rate is two cups per plant for large roses and one cup for smaller plants.
After the first bloom cycle, usually June 1-15, the plant will need an additional feeding. You may choose to apply a 12-12-12 formulation at one-half cup per plant or apply a faster acting water soluble application. If using water soluble fertilizers, the suggestion is to use at two week intervals.
Since roses tend to take some rest during the heat of the summer late –June to July – water becomes more important than fertilizer.
In late July, you may want to add an additional application of organic fertilizer. Also at this time you may continue with an addition of granular fertilizer (rose formulations or 12-12-12) or two week intervals of water soluble. Fertilization should stop by early September so that plants will not be rapidly growing going into winter.
- Chemical fertilizer will burn if not watered before and after use.
- Most important times to feed roses – at pruning and after the first bloom cycle.
- Most plants will do well with one application of fertilizer per bloom cycle (30-45 days).
- Do not over fertilize miniatures.
- A combination of chemical and organic programs is desirable.
- Organic fertilizers are slower acting but contribute organic matter and micro-organisms.
- Plants will tell you if they are thriving. They will also tell you when they are struggling. Make observations.
- Fertilization programs vary from rosarian to rosarian and will also vary from year to year. Find what is successful for you to achieve the desired results.
When in doubt, contact a Consulting Rosarian from your local rose society. See the consulting rosarian contact list HERE.