What are guidelines for fertilizing annual and perennial flowers
with nitrogen and phosphorus? —Rosanne Janssen, Wichita, KS
Plants need both major and minor nutrients. Minor nutrients
(also called “trace elements”) are usually supplied by the soil,
but plants use major nutrients in large enough quantities that
we should add them regularly. Of the major nutrients, nitrogen
(N) is associated with green, vegetative growth; phosphorus (P)
is associated with flowering; and potassium (K) aids root
development. However, that’s an oversimplification. All three
major nutrients are necessary, to some degree, for all aspects
of healthy plant growth. If plants don’t have enough nitrogen or
potassium, they’re unlikely to flower well, even though there’s
plenty of phosphorus in the soil. There is no one best
fertilizer formulation for annuals or perennials. Many work
well. However, choose a fertilizer that’s higher in phosphorus
and potassium than nitrogen to encourage blooming and discourage
excessive leafy growth. If yo