On Jan 6, 7:00*pm, Higgs Boson wrote:
That has always been my weak point. *I know (barely) not to fertilize
when plants are dormant, but I always stumble when, e.g., to fertilize
my roses after mid-January pruning.

I have two young fruit trees (Plum and Apricot) which are just
shedding their leaves, and two blueberry bushes in large pots, one of
which is confused enough to be blooming and setting fruit.

I also have growing "winter" vegetable crops that, I assume, it's OK
to fertilize: Peas, beets, carrots, green onions, bok choy, stuff like
that.

Is there ONE comprehensive "when to fertilize" rule? *Geared to my
mild "Mediterranean" climate -- So. Calif coastal?

Balanced (5-10-10, 10-10-10, 20-20-20) with secondary and
micronutrients when the plant wants it -- leaves will show
yellowing or spotting. Higher N is used for foliage, P and
K for fruiting and flowering. Synthetics (Peter's, Miracle-Gro)
are faster release than organics, less likely to burn or be
overapplied HOWEVER organics can get you in trouble
if excessively overdone. Fish emulsion is wonderful
fertilizer, but excess, especially in soggy soil, breeds
fungus gnats or other pests. Root damage from gnat
maggots impairs nutrient uptake. If infestation isn't
obvious, you end up pouring on more fertilizer, which
makes the problem worse, making you pour on still
more fertilizer, breeding still more maggots. If you
need to resort to bug killers, your "organic" plant
food is no longer so "organic."