On 9/22/2009 5:53 PM, David E. Ross wrote:
On 9/22/2009 6:55 AM, Alistair Macdonald wrote:
From a bed of around 100 hybrid rose bushes, this year again I have lost
about ten plants, this after a rather poor flowering season. The bed is well
covered with forest bark but which I feel is not allowing any feed to
penetrate satisfactorily. I want first of all to provide a better feed than
Growmore, and also to plant new rose bushes to replace those lost. What
fertiliser(s) should I use for the existing bushes and what, if different,
for the new ones? I have been recommended bone meal and sulphate of potash
with a handful of Epsom salts to each, both old and new bushes. I would also
appreciate any advice on applications.



If the bark is a mulch, fertilizers should sift at least part way
through it. When you water, the fertilizers should then dissolve and be
transported downward and into the soil.

If you want something with a systemic insecticide added, I use Bayer's
2-in-1. I feed my roses monthly and use Bayer for alternate feedings.

When I don't use Bayer, I use a handful of ammonium sulfate. Roses like
a lot of nitrogen and they like an acidic soil. Ammonium sulfate
provides both.

For the first feeding of the year, I use (in declining amounts from
handful to tablespoon):
ammonium sulfate
gypsum (calcium sulfate)
iron sulfate
Epsom salts (magnesium sulfate)

The gypsum not only provides calcium but also reacts chemically with the
heavy clay in my garden, making the clay more granular and less pasty
and allowing water to penetrate better. The magnesium in Epsom salts
promotes the growth of new canes.

You will note that I don't use either bone meal or superphosphate (both
being sources of phosphorus, which promotes flowers and root growth). I
put a generous amount of the latter in the planting holes when I first
planted my roses. This should be sufficient for at least 10 years.
Phosphorus tends not to dissolve or leach through the soil. Instead, it
must be placed where plant roots will find it. For older plantings, you
can take some 1/4-inch rebar and poke holes 2 feet deep around the plant
in a circle about 2 feet in radius. Half fill each hole with bone meal
or superphosphate, and then finish filling each hole with fine compost.
Bacterial action from the compost will very slowly make the phosphorus
available to the plant roots.

The vigor and flowering of roses depends very much on how they are
pruned. My http://www.rossde.com/garden/garden_rosepruning.html is
NOT a how-to guide; it describes my approach to rose pruning.


I forgot to mention this: Roses like abundant moisture. No, they do
not want soggy soil. But the soil should be constantly moist.

Since overhead watering promotes fungus (mildew, rust), it's best to
irrigate by "flooding", allowing a hose to fill a basin around each
rose. If there is a slight slope to the bed, basins can be connected so
that you don't have to keep moving the hose.

Alternatives include drip irrigation or bubblers connected to your
regular garden irrigation system. I use drip for my roses in front. A
public garden where I'm a docent has a bubbler for each rose bush.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at http://www.rossde.com/garden/diary