The Complete Guide to Landscape Design, Renovation,
by Cass Turnbull
FERTILIZERS AND ORGANICS
The biggest difference in the health and looks of your shrubs and
trees is, once again, going to depend mostly on whether or not you
have poor soil, poor drainage, or too little irrigation or plants
which are ill-suited for their sites (i.e., shade lovers in the
sun). Fertilizers cannot make up for deficiencies in these areas
any more than pruning can. Fertilizers can, however, make a significant
contribution to the overall robustness and health of your garden
subjects, once their basic needs are met.
Plants do not eat fertilizer; they manufacture their food from sunshine.
They also "breathe" air not only with their leaves, but
the trunks of trees and their roots need access to air. The base
of a tree is apt to smother if covered over with soil during construction.
Plants use the CO2 in the air and give off O2 as a waste product
(lucky for us). Plants take up water and elements and simple compounds
from the soil to complete biological activity. Plants use, in order
of most needed, Nitrogen, Phosphorous (P2O2) and Potassium or Potash
(K2O), or N-P-K as they are usually called. The three numbers on
your fertilizer bag always stand for the percentage by weight of
these three elements in that same order in the bag. If you have
all three numbers, then you have what's called a "complete
fertilizer." Plants also use minute amounts of what are known
as micro nutrients. A deficiency in one of these may affect your
plant, though this is rather uncommon. Mostly, it is said, plants
Fertilizers vary in their relative amounts of N-P-K and in the specific
form of each element. But it's all the same stuff, basically. You
don't "feed" your roses something different than you put
on your lawn--it's just in relatively different amounts, the N-nitrogen
of N-P-K is primarily known as good to produce leafy green growth.
The P and K are used to assist in making bigger flowers, better
roots, for winter hardiness, and disease resistance. Your grass
fertilizer will be heavy on nitrogen, your fertilizer for flowers
or vegetables will have more P and K. Bigger numbers on the bag
simply mean it's in a more concentrated form. People who understand
math will use these numbers in a formula to compare prices of different
bags of fertilizer to find out which one gives you the more bang
per buck. Also, they calculate application rates for their fertilizer.
The general rule is two to six pounds of actual nitrogen per 1000
square feet per year for lawns, less for shrub beds. Adjust your
fertilizer spreader to distribute fertilizer at the correct rate.
Go to an empty lot, pace off 100 feet by 10 feet (= 1,000 square
feet), put two pounds of real nitrogen (a percentage of the bag
according to label) and adjust it until it comes out right. The
same method can be used to adjust the rate of application for liquids,
except you can use water during the trials and also calibrate on
an easy-to-measure concrete surface, like the driveway. When measuring
it is useful to remember, "A pint is a pound, the world around,"
thus converting weight into volume.
Fertilizers come in different formulations--some are simple enough
to be taken up by the plant immediately but won't hang around long
in the soil--a shot in the arm--needing to be reapplied more often.
Fertilizers with more complex compounds break down more slowly,
releasing their goodies to the plants over time and are less likely
to burn roots. Some, like Osmocote ___, are coated with something
that allows the fertilizer to be released when the weather is hotter
and the plant needs it more. It is often used by nurseries for potted
plants and for annual flower displays (marigolds, impatiens, etc.).
Fertilizers can be as complicated a subject as you care to investigate.
You can load up on the various types and investigate for the best
time for each plant. And, no doubt your plants will additionally
benefit from the tailored care and attention. Or you can do like
I do. I use a general, all-purpose shrub fertilizer in the late
spring, and a grass fertilizer for my lawn in the late fall. Fertilize,
if you can, when it's going to rain soon or water it in. Chemical
fertilizers can burn leaves or roots if put on too heavily. People
often burn up their lawns by applying too much fertilizer and then
not watering it in. Fertilize in moderation. Running your plants
at full steam ahead can damage them just as much as letting them
starve for a little phosphorus. Use too much nitrogen and you have
too many green soft shoots at the expense of flowers, fertilize
too late and your plants may not harden off for the winter and get
caught in an early frost. People, as always, get into trouble by
using too much of a good thing. Give them what they need to be healthy,
but don't push them.
To avoid over fertilization I usually play it safe and get the lower-numbered
sacks (numbers under twelve). To spread your fertilizer you can
put it in a bucket and broadcast it. This means that, with your
rubber-gloved hand, you just randomly throw it around, up in the
air in a sweep as you walk. Avoid clusters of fertilizer pellets
on the ground, which will cause burning or yellowing of grass blades.
Then go back and "bang the bushes" to knock off excessive
pellets. Others may choose to carefully sprinkle a light circle
of fertilizer at the dripline at the base of the shrubs. You can
also, for large areas and for more even coverage buy a plastic broadcast
spreader. By turning the crank it just flies out at a relatively
Drop spreaders are those carts used by lawn worshipers to
fertilize their lawns. Use this tool when applying a weed and feed
which contains a broadleaf weed killer. If you put that in a cyclone-broadcast
spreader it would go flying off into your shrub beds, killing broadleaf
shrubs as well. Drop spreaders are trickier to get even-looking
green grass. You have to divide your fertilizer into two parts and
walk very straight lines--back and forth one way and then go the
other way. If you inadvertently over fertilize or miss a section,
the lawn will tell on you later, showing either streaks of lighter
green or scorched yellow grass.
Be sure to wash yourself and your spreader after fertilizing; chemical
fertilizers can be quite corrosive. Be careful with compounds containing
iron (used for quick greening) as they can stain your concrete paths.
Chemical Vs. Organic Fertilizers
Plants are not damaged by giving them "chemical" fertilizers,
but the long-term fertility of the soil may be degraded if it receives
no other help than this. There are serious concerns that the over-application
of nitrogen in chemical fertilizers is leaching down and contaminating
ground water. This concern has been directed mainly to the agricultural
use of fertilizers, but can reasonably be considered to apply to
urban use as well. The longer I am in the business, the more I tend
to throw my hand in with those of the organic philosophy.
All plants take up N-P-K in the same form; however, organic fertilizers
have to be processed down into simpler compounds for the plants
to take them up. Worms and entire communities of fungus, bacteria
and protozoa do this work. This is good. They are attuned to the
rhythms of nature. These micro organisms can't multiply and do their
work until the ground warms up sufficiently in the spring. This
keeps plants from growing before the time is right. With chemical
fertilizers, on the other hand, all nutrients are readily available
and can be used immediately, perhaps before they should be or when
the plant should be slowing down in the fall.
Organic fertilizers are generally safer to use because their concentrations
are much lower. The only common trouble I've heard of is that utilizing
uncomposted manure-- specially chicken manure--can burn plants.
This is why garden books always refer to manure as "well-rotted
manure." Straight from the stables, manure can also contain
unwanted weed seeds, and we know about them! Properly composting
manure will eradicate most seeds, and the powdered stuff you buy
in bags at the hardware or grocery store (or nursery) will be steamed
or heat-treated to destroy seeds. It's great stuff!
Dried powdered manure can be spread just like chemical fertilizers.
Some people go back and hoe it in or use a cultivator to sort of
scratch it in. The fresh stuff, and especially if it gets wet, will--well--stink
for a few weeks. If you can, apply it when it's cooler and raining
a lot for this reason. After a week you'll no longer notice the
smell. I don't mind the smell. To me it is "the smell of victory!"
(to quote a line from the movie, Apocalypse Now).
Many insist that manure and compost are not fertilizers at all,
since the actual nitrogen, phosphorus and potash available to or
readily usable by the plants is small. They are, however, very good
at feeding and sheltering the bacterial organisms and earthworms
that do indeed create fertilizer.
Not all so-called organic fertilizers are organic (meaning once
alive). Some are mined, like lime or phosphorus. Others, like blood
and bone and fish meals were once certainly alive. The discovery
that crop production could be increased with the addition of crushed
bones to the soil allowed a hungry Europe of late 18th Century with
a new, expanding city population, to continue to be supported by
limited farmlands. England was accused of widespread pillaging of
soldiers' cemeteries of Europe, to supply their farmers. The reliance
on bone meal ended when it was discovered that the same nutrient-building
compounds could be mined in rock form.
Nitrogen fertilizer in its first, most basic form--urine--is still
used by organic gardeners. Some even use their own--diluted. Wood
ashes are another classic source of useful compounds. Also, cottonseed
meal, kelp and sludge (another human "fertilizer.")
What is it about these organic compounds that causes gardeners to
talk about them with the same sort of glee that a chocoholic uses
in describing a new dessert bar in town? Organic gardeners have
experienced the joys of building up the perfect, healthy, living,
thriving, fertile ecosystem we call soil.
Good soil is not just dirt. And the fertility of soil is more than
the amounts of N P and K it contains. These elements must be available
to the plants, and that depends on a host of other factors like
the pH (acidity or alkalinity) of the soil, the cation (pronounced
cat-eye-on) exchange capacity, the water holding capacity of soil,
the size of soil particles, its texture, and air spaces. It does
only temporary good for a sandy soil landscape to add chemical nitrogen,
as the sand cannot hold it. The nitrogen will sluice through--perhaps
polluting the water table. Whereas adding organic material will
allow the soil to "hold" nitrogen and release it slowly
to the plant. Organics not only add "nutrients" to the
soil; they give it good soil structure. Furthermore, humus will
act as a stabilizer for organic life.
We are now moving from organics as fertilizers to organics as amendments.
We will need to interpret some of these new gardenese verb-nouns
for you backyard neophytes.
Organic - means it was once alive
Amend - a verb - means to add something to your soil, usually
by digging it in.
Amendment - a noun - the stuff you are digging in to your
soil. Your soil amendment could be organic--like leaves--or inorganic--like
Mulch - verb - you remember, to spread a layer of something
over your soil.
Mulch - noun - the stuff you put on top of your soil. Mulches
can be organic--like sawdust--or inorganic--like black plastic,
Organic matter - the fresh stuff, like leaves, grass clippings,
shredded bark, peat moss.
Humus - organic matter that has sat around awhile and has
been partially decomposed by bacteria. Leaf mold fits nicely into
this category. That's just that old pile of leaves that's falling
apart, but you can still tell it's leaves.
Compost - noun - organic material that has been wholly decomposed
by microbiological activity. Compost is usually made of green stuff
(grass clippings) and brown stuff (autumn leaves, twigs), that's
been kept in a heap for anywhere from three weeks to one year, whereupon
it turns miraculously into dark, clean, earthy-smelling crumbly
particles that look like dirt. People who compost love the fact
that they have taken a troublesome waste product and turned it into
"black gold" that you can't even buy at the so-called
Compost - verb - the process of turning organic material
Now let's see if you can use these terms in sentences. One can mulch
with compost or amend with compost. Or one could mulch with mulch,
compost, or inorganic material, say red cinder rock. But one could
never compost inorganic material, rocks just take too long to decompose.
It is said that musicians don't die, they just decompose. Sorry,
it's an old joke.
Building good soils by mulching with compost or humus becomes an
obsession with most good gardeners. Unlike chemical fertilizers,
compost feeds the whole ecosystem and keeps it healthy, not just
the plants. I have done a little reading on compost, and its virtues
are too numerous to explain here, but its most engaging quality
seems to be its ability to solve totally opposite problems or imbalances
in the garden. Soil too sandy? Add compost. Too much clay? Add compost.
Soil have too many heavy metals or not fertile enough? Add compost.
Compost seems to have a stabilizing effect in nature and its benefits
are long range. Besides the plants love it, it looks good, it smells
good, and it feels good in your hands.
A fairly easy compost program entails making a four- cubic-foot
pile of leaves layered with grass clippings. Ideally, you use two
parts grass to one part leaves. If you have a lot of room and a
lot of organic material to get rid of, you can graduate to a hot
compose system. There are several good books that explain hot composting.
The heat generated by decomposition of the organic material is great
enough to kill most weed seeds and disease organisms. So you can
add more and different things to these piles, like weeds.
Composting, like most gardening, and even most of life, I guess,
can be as simple or complex as you like. The mother of a friend
of mine is a devoted gardener. He visited her one day and she proudly
showed him her new three-bin compost system. Then she nipped inside
to get a packet of something she sent away for in the mail--Compost
Starter. Adding water to it, she then poured it reverently into
one of the bins. "My god, Mother! exclaimed her son, "that's
not a hobby, that's a religion!"
If making your own compost seems like too much trouble, you can
buy it in bags or have a pile delivered to your house in many cities
now. Commercial material is probably hot composted and the possibility
of spreading weed seeds and plant disease is not a concern.
Even more fascinating, I find, are worm boxes on display at my local
Tilth Association demonstration garden, and at local nurseries and
garden fairs. These are boxes wherein you place special starter
"worms" and shredded newspaper--to these you add your
table scraps. Miraculously, the worms multiply and the scraps turn
into worm castings to be applied to your garden. Castings need not
be broken down further for plants to use. Castings are fertilizer.
They are, if you will, the straight poop. The reason robins can
pick worms off so easily is because worms, being clean-living organisms,
return to the surface to leave their castings. Don't underestimate
the worms in your yard. Worms constantly mix and stir the soil,
aerating it perfectly for roots to push through easily. They create
vast and incredible amounts of fertilizer for your garden.
When you have good soil, you have worms and often when you have
worms, you have moles that love to eat them. I was at a nursery
recently when a customer asked how to get rid of moles. The nursery
person recommended a product that when applied to the ground would
gas all the worms to death, thus removing the moles' food source--presumably
causing the moles to leave. Kill all the worms? Horrors!
Although occasional moderate use of chemical fertilizer is by all
means acceptable, I encourage people to avoid over-reliance.
To sum up my own feelings about fertilizers and organics, I quote
from the Washington State University Cooperative Extension Service
bulletin #0648, Organic Gardening: "Your Long Range Objective
should be to build your garden area to a high fertility level and
then to maintain fertility through composting and mulches, reducing
reliance on commercial and organic fertilizers."
Fertilizer bags all have three numbers on them that stand for the
amount (percentage by weight) of Nitrogen (N), Phosphorus (P) and
Potassium (K). Nitrogen is, generally speaking, good for producing
green growth. The P and K are for better roots, blooms, disease
resistance and hardiness.
Don't overuse chemical fertilizers. You burn roots or leaves with
over application or if you fail to water. Lower-numbered (numbers
under twelve) sacks are less concentrated and therefore safer. Don't
fertilize too early or too late, too often or too much.
Use organics; mulch, weed-seed-free compost, or dried manure to
improve the long term fertility of the soil.
People always try to use pruning and fertilizing to make up for
bad planning. Remedial pruning and fertilizing can only help to
a certain point.
I think of chemical fertilizers in the same way as vitamin pills.
They are no substitute for a healthy diet. Your soil will benefit
greatly from a regular feeding of organic mulch.
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