How many of us humanize our pets and other animals? If it was a show of hands I’ll bet the room
would look like an Adele concert.
This Anthropomorphism of things doesn’t stop
at animals though. I’m sure there would be at least one or two of us that treat
our plants in the same manner. They are great listeners after all and love you
unconditionally if they are fed and watered. But do they really?
One way we are told to care for our plants and help them
develop is to use the “Companion Planting” method. The idea of this is to mutually benefit each
plant in some way. Certain herbs are said to keep away greenfly for example and
others such as marigolds (the calendula type) and nasturtiums are so soft and
delicious that blackfly with flock to them instead of your prized broccoli and
beans. Where does this idea come from though and is there really any truth in it?
The idea sounds great but proving it works is a different matter.
Origins
I would imagine the idea has been around for thousands of
years. Plants were associated with the four elements (earth, air, fire and
water) and/or signs of the zodiac. One
of the outcomes of this categorization was the agricultural practice of
planting together those species that “love” each other anthropomorphism
reflected in a few popular books and many posters.
One of the earliest recorded manipulations of nature
resembling companion planting was the ‘Three Sisters’ idea in north America.
Corn, beans and squash were planted together. Beans are nitrogen fixers, corn
stalks are strong enough to support the beans climbing and the squash vines
provide shade for the soil, reduce evaporation and deter unwanted competition
from other plant roots. The plants complement one another and don't compete for
the same things.
The phrase “companion plant” is now used in both science and
pseudoscience, so that its intended meaning is unclear. The science of
companion planting has become a little blurred over the years and often gets
confused with myths, crystal formations, which apparently tells you which
plants "love" each other and the plants rhythm and vibrations. Because of this the phrase companion planting
now gets more accurate definitions such as "Intercropping" or
"polyculture"
Ecologists now use the term "Plant Association" to
define the natural relationships towards plants.
Most research focuses
on the attraction of beneficial insects to plants. Certain plants can also
disrupt the ability of herbivore insects to find suitable host plants to lay
eggs on. The theory is that it wastes the insect’s time laying eggs in the
wrong places. Many plants share
mycorrhizal (known as the soil web) in the soil, so share nutrients such as
nitrogen some plants are totally reliant on host plants for this. The venus fly
trap gets it's nitrogen from flies, but that's another story.
There are other ways plants benefit each other, a few dry
climate plants accumulate salts so this could benefit salt sensitive plants
while others take up heavy metals which decreases the toxic affect to more sensitive
plants and then there are the nitrogen fixers.
Static
Plants don't move around themselves so need to adapt to their
environments. Those with a narrow range of tolerances (such as my chamomile)
will soon be pushed out by other more invasive plants of not enough sunshine,
the wrong Ph. of the soil and a host of other issues. Some plants can even
change their environment to suit their growing needs, large leaved plants can
give the ground a lot of shade and stop other plants from challenging them for
example. Changes such as this are happening all of the time in the landscape,
ever changing and adapting.
Linda Chalker Scott (from the Garden Professors Blog) really doesn’t like the term ‘Companion
Planting’ but thinks there is validity in some of the practices.
“There is no scientific basis, however, for any of the
several lists that exist describing “traditional companion plants”. Like horoscopes, these lists may be fun to
use, but they should not be perceived or promoted as scientifically valid any
more than astrology. Furthermore, those
of us who value the science behind our horticultural practices should avoid
using this phrase for precisely the same reason.
The Bottom Line
•The phrase “companion plant” is too vague to be useful to
plant scientists and professionals; “intercropping” and “plant associations”
are more definable and credible
•Documented benefits from plant associations include
physical, chemical, and biological alterations that can improve the
establishment and survival of desired plant species
•Pseudoscientific, mythological and occult applications of
“companion plantings” are not scientific and will damage your credibility as a
professional
•Traditional “companion plant” charts have entertainment,
not scientific, value
For me it’s about diversity, experimenting and fun more than
academic papers. But for now I won’t be recommending companion planting I’ll
suggest “Intercropping” That should clarify things… or will it?
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