On 2/11/2015 4:29 PM, Hypatia Nachshon wrote:
On Wednesday, February 11, 2015 at 9:36:41 AM UTC-8, David E. Ross wrote:
On 2/11/2015 8:32 AM, Hypatia Nachshon wrote:
On Monday, February 9, 2015 at 3:49:51 PM UTC-8, David E. Ross wrote:

My roses are already showing leaves, so I fed them yesterday. I gave
them a mix of ammonium, iron, and magnesium sulfates (listed in
declining amounts).

Tx, David. How is this different from commercial rose food from nursery?
I don't have one handy to compare formulae.

TIA


Commercial fertilizers often contain phosphorus, which is a waste of
money and a potential pollutant. The problem is that phosphorus --
which promotes flowering -- does not readily dissolve. Instead, it must
be placed where roots will find it. That is why I always place either
bone meal or super-phosphate in the bottom of planting holes when
planting something. Also, every 5-10 years or so, I take a piece of
steel rebar, poke holes about 1-2 feet deep in the root zone of my
roses, and then fill the holes with super-phosphate.

Furthermore, roses prefer an acid soil. That is why I use sulfates.
Most commercial fertilizers are relatively neutral.

Despite all that, I do use a commercial fertilizer. I feed my roses
monthly from the time new shoots appear after pruning until late
October. After the initial feeding with ammonium, iron, and magnesium
sulfates, I alternate between only ammonium sulfate (nitrogen) and a
commercial fertilizer that contains a systemic insecticide. The
instructions for the commercial fertilizer say to use it every 6 weeks,
but I only use it a full two months apart. I never see aphids, spider
mites, or bark borers.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary

Most informative, tx.

Two further q's:

Why would (commercial)) phosphorus be a "potential pollutant".

Because the phosphorus disolves so slowly, it is more likely to wash
away and enter streams and lakes. Eventually, it will disolve and then
cause excessive algae growth. As the older algae die, their
decomposition consumes more oxygen than the living algae produce,
leaving insufficient oxygen for fish and other aquatic animals.

Which commercial fertilizer avec insecticide do you use?

TIA

I use Bayer 2-in-1 rose and flower care. It contains Imidacloprid,
which should be used sparingly since it is quite harmful to bees.
Although not approved for use on edibles, studies indicate it is
harmless to birds and mammals (including humans). Thus, I use an
Imidacloprid drench on my peach tree to prevent flat-head bark borers;
but I use it only after the tree has finished blooming. I also use
Imidacloprid on my dwarf citrus to treat leaf miners, but only after I
see actual leaf miner damage and not when the trees are blooming or
about to bloom.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary