36 Basic Perennial Garden PlantinG & Maintenance
organic matter, soluble salts (too high a concentration will hinder plant growth),
and heavy metal content (if applicable). If they don’t offer this information, I
urge you to request a test to be run, because not all soil amendments are the
same. Soil companies also will usually provide recommended application rates
for their product; it is advisable to follow them. The higher the organic matter
content of the material, the higher its soil-conditioning properties. For composts
with a high nutrient content, overapplication of the product can injure or kill the
plants. Work with your compost supplier to find the best product and to help
determine the proper rate.
Organic amendments should be free of weeds, insects, diseases, and foreign
material. I had the unfortunate experience of buying a compost that was full of
weed seeds on one of my jobs. When the seeds began to sprout, well after
planting, correcting the problem entailed having the weeds analyzed first to find
out if they were annual or perennial (a key concern in this brand-new and large
perennial planting), then trying to have the compost company stand behind its
product, while satisfying the client at the same time. Definitely something to
avoid if at all possible—know your source.
As I mentioned earlier, you can mix some of the soil amendment with your
existing soil (in the proper proportions) and have the mixture tested by a soil
testing lab for very specific and accurate recommendations.Types of soil amendments
There are many different types of organic soil amendments from which to
choose. Again, what you choose will depend greatly on what is locally available. I
will share with you what is generally available in my area for landscapers and
gardeners. I will also indicate the approximate nutrient analyses of these
particular amendments. Remember, always test your own! I will not discuss the
raw ingredients for various composts—leaves, grass clippings, sawdust, raw
manure, hay, and others—as these materials should be composted first before
being added to the perennial garden. Incorporating uncomposted woody
(high-carbon) materials into your soil can rob nitrogen from the soil and starve
your plants for a year or more as microorganisms work to break them down.
Incorporating uncomposted high-nitrogen materials into your soil can burn
sensitive plants.
leaf humuS Supplies a wide range of essential plant nutrients. One leaf
humus product that is available to me is about 38–43 percent organic and has pH
7.7, with a nutrient analysis of 1.0–0.4–0.5, referring to the percentage of
nitrogen, phosphorus, and potassium (N–P–K) by weight. Keep in mind that oak
leaves are acidic and maple leaves are more alkaline, so the incorporation of
either in your humus will affect the pH of the material.
c anadian Sphagnum peat moSS Provides very low nutrients (less than
1 percent N) and is acidic, with a pH of about 4. Canadian sphagnum peat moss is
excellent for improving aeration of clay soils to increase drainage, and it
improves the ability of sandy soils to hold water and nutrients. It is sterile and
weed free. When used in combination with compost it helps reduce compaction
that can sometimes occur when compost is used alone. Depending on the
climate, peat can take several years to break down in the soil, as compared to
composts (which can be partially broken down within months) and manures
(which break down in several weeks). Canadian sphagnum peat moss, which
grows at 50 times the rate at which it is harvested, has proved to be a sustainable
resource. Its use is environmentally sound.
Sphagnum peat moss should not be confused with the dark black peat (muck
soil) often sold and used like topsoil. Dark black peat is so far along in its