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Fertilizing is synonymous with production in
roses. Plants must be fed if they are to remain healthy and produce good
blooms. You must return to the soil quantities of nutrients equal to
those being consumed by the plant.
Strictly speaking, there is no such thing as an organic fertilizer.
Organic materials feed the soil bacteria, and they in turn break it down
into inert mineral salts, the only form in which the plant is capable of
absorbing them. However, organic materials are essential for a
well-conditioned soil.
Chemical fertilizers are generally
faster-acting than organic materials, since they require only
dissolution in water to become available to the plant. (Not necessarily
better, but faster.)
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 blooms; while potassium or
potash stimulates the general health of the plant.
Always water well before and after an
application of granular fertilizer. If dry fertilizer gets on the
leaves, rinse it off immediately.
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 a cool spring.
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 minerals.
One to two handfuls of granular fertilizer
applied in April, June, and August will suffice. Avoid applying any
fertilizer containing nitrogen after early September.
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 two cups per
plant worked lightly into the soil in the spring. (Use only pellets or
meal with no added salt.)
Epsom salts (magnesium sulfate) is also
useful to the plant if you are not regularly applying dolomite lime
(which contains magnesium sulfate). Approximately 1/3 cup per plant in
the spring is recommended at least every other year. (If dolomite lime
is applied once or twice yearly to rosebeds, this will provide the
needed magnesium, and no Epsom salts need be added.)
Fertilizers are of little value if your
soil is out of balance. A pH range of 6.0 to 6.8 is best for roses. Here
in the western Pacific Northwest, soils tend to be acid and may need an
addition of lime to be with the needed range. Test your soil
occasionally and correct if necessary.
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