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Seattle Rose Society

ROSE CARE

Fertilizing Roses



Fertilization is synonymous with production in roses. Plants must be fed if they are to remain healthy and produce good blooms. You replenish the nutrients consumed by the plant.


Strictly speaking, there is no such thing as an organic fertilizer. Organic materials feed the soil bacteria, which, in turn, break it down into inert mineral salts, the only form in which the plant is capable of absorbing them. Chemical fertilizers are generally faster acting than organic materials, since they require only dissolution in water to become available to the plant. However, organic materials are essential for a well-conditioned soil.


All products labeled as fertilizer must, by law, have the percentages of nitrogen, phosphorus and potassium listed in that order (N-P-K) on the container. Nitrogen produces vegetative growth; phosphorus promotes the root system and the bloom; potassium or potash stimulates the general health of the plant. If a granular commercial fertilizer is used, choose one with a general balance between the three main chemical ingredients and, if possible, one that also contains trace elements.


Soil bacteria are dormant until the soil warms up in the spring; therefore, too-early applications of fertilizer in the soil are wasted. However, some benefit can be obtained by foliar feeding plants with a water-soluble plant food during cool springs. 1-2 handfuls (use gloves, or a 1-cup measure) of granular fertilizer applied in April, June and August will suffice. Do not apply any fertilizer containing nitrogen after mid-September. Always water before and after applying granular fertilizer. If dry fertilizer gets on the leaves, rinse it off immediately.

Osmocote™ and other time-released fertilizers can be applied to the soil at pruning time and will adequately feed the plant for the entire growing season. However, most rosarians will supplement this with occasional granular or water-soluble fertilizers.


Alfalfa pellets contain a valuable growth hormone and make an excellent feeding supplement - about one cup per plant worked lightly into the soil in the spring.


Epsom salts (magnesium sulfate) is also useful to the plant. Approximately 3 oz. per plant in the spring is recommended at least every other year.


Gypsum is another supplement that will curb salt buildup, provide calcium, and prevent soil compaction and improve drainage. Two cups per plant per year is adequate.


Fertilizers are of little value if your soil is out of pH balance. A pH range of 6.0 to 6.8 is best for roses. Test your soil occasionally and correct if necessary.

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