Horticulture for the home gardener /County of Los Angeles, Department of Arboreta and Botanic Gardens.

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wines

; and inorganic
Organic fertilizers u

Nitrogen is needed for the development of foliage. Fertilizer intended. for
lawn grasses or other foliage plants generally contains the highest propor-
tion of nitrogen. Because the nutrient moves from older to newer leaves,

the older leaves will be the first to become yellow and lose the rich green
color in the leaf veins in a nitrogen poor situation. An application of too
much nitrogen, however, could result in weak, rapid growth and insufficient
bloom. When uncomposted sawdust or straw mulches are used, bacteria which
decompose the mulch draw on the plant's nitrogen supply, thereby causing a
deficiency. To correct this situation, apply additional nitrogen before mul-
ching with such materials.

Phosphorus, the second number listed on a fertilizer label is needed by
plants to convert sunlight into the energy needed for growth. A fertilizer
high in phosphorus is usually applied to plants to encourage the production
of fruits and flowers. Lack of phosphorus discolors young leaves, giving
them purplish margins or a deep green color with dying tips. Phosphates
move slowly in the soil even when there is plenty of moisture; the nutrient
must either be dug in deeply or kept in abundant supply so there is always
some phosphate moving into the plant's zone of use.

Potassium, the last number listed in the fertilizer formula, is required
in greater quantities than all other elements except nitrogen and calcium.
It aids in the formation of starches and sugars, speeding the buildup of pro-
teins to form sturdy, disease resistant plants. Tip and marginal leaf burn
of mature leaves, weak stalks, small fruit, and slow growth indicate a defi-.
ciency of soil potassium. Potassium travels through the soil more easily
than the other primary elements and is often leached out of the soil by winter
rains.

APPLICATION

In the U.S. more than 1.5 million tons of chemical fertilizers are sold annu-
ally, mostly in granular form. The easiest way to apply granular fertilizer
is to scatter it over the planting area according to directions, and water it
in immediately. Care should be taken that it is not applied directly on moist
foliage or it may burn the young growth. Liquid fertilizer may also be applied
through a hose applicator and watered in.

The timing and amount of fertilization will vary from plant to plant. Gener-
ally, plants benefit most from small quantities of fertilizer applied frequent-
ly during the growing season. If the needed elements in the soil cannot be de-

termined by plant symptoms, soils can be analyzed through the commercial nur-
series.

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