Using Plant Diversity to Eliminate Garden Pests

Even though I’ve been successfully gardening
for 15 years (and not very successfully for several years before that), I can
echo the sentiment expressed by Thomas Jefferson:  “[T]hough an old man, I am but a young
gardener.

As I mentioned last month, I
participated in a three-day gardening boot camp back in August at a ranch about
1.5 hours from here.  I wasn’t convinced
that it would be worth the $500 tuition, but Lydia wanted to attend, so off we
went.  I posted a link to William DeMille’s
website where you can check out the class as well as find a link to his free
weekly Q&A session on Zoom.  And no,
I haven’t received any compensation of any kind for mentioning his class or
website.

Anyway, it was worth the
money.  I’m trying to figure out if I
want to attend again.  Actually, I
already decided that I do want to; I haven’t figured out how to persuade my
husband that I should.  Becky has had it
with her job and is ready to quit and homestead full-time and is considering
his 17-week course. 

That said, there is no way to
condense everything I learned into a single blogpost or ten.  Using plant diversity to eliminate garden
pests is just a small part of the big picture. 
And at the start of this topic, I’d like to point out that I took William’s
class in August, quite a few months after I’d already planted the garden, so
what I observed and experienced wasn’t a result of his class.  I just learned a bit about why what I did
produced results. 

As regular readers know, most of my
backyard is a “stealth” garden.  There
are no regular rows of crops, no raised boxed beds.  The living room looks out on the backyard and
my husband didn’t want to see a formal veggie garden.  So there are curves and flowers and shrubs,
an arch and a grass path, and a dry creek. 
I hope to add a bridge over the dry creek next year and will be
expanding the growing plots.  And the
vegetables are all mixed in.  I did
decide that there were too many flowers this past year, so for this year I hope
to replace some of them with veggies. 

Due to the extremely long winter, I
didn’t get to even begin working in the garden until mid-April.  The cabbage and broccoli starts went in the
ground right away, and I put some nasturtium seeds in as well because they ward
off cabbage moths, but they took a long time to germinate.

It was an odd year for
insects.  I found exactly two aphids, one
in the spring and one in the fall. 

There were a lot of cabbage worms
before the nasturtiums got growing.  I
sprayed them—and only them—with Bacillus
thuringiensis (Bt) once or twice early on. 
No more worms.  However, their
butterflies were all over the garden all season long.  Loads of them.  I don’t know where they came from, but I do
know they didn’t come from worms that had feasted on my veggies.  I also had several hummingbird moths that
morph from tomato hornworms and do no damage to vegetables.  But there was only one hornworm—a huge one—on
a fringed willow herb.  The roly-polies
disappeared.  I’m still working on the
slugs, but I believe their days are numbered. 
I had maybe half a dozen earwigs in all my apples last year.  And while I don’t know how many bushels we
picked, I canned about 7 dozen quarts of applesauce.  That may have more to do with keeping the
ground free of apples which house the worms over the winter.  There were loads of mason bees and other
insects, but I saw no honeybees until the end of fall.  The neighborhood beekeeper lost his hives
over the harsh winter.  Oh, and there
were also a few Mormon crickets.  I am a
little concerned about those for next year. 

I attributed the lack of aphids,
hornworms, and roly-polies to the harsh winter, but it seems that there was
something else in play.  And that was one
of the gems I picked up in the boot camp gardening class in August. 

Like with the animal kingdom, pests have been found to prey
only on weakened, diseased plants.  Cue
the cries of protest—“my veggie plants were gorgeous, yada yada yada, and they
got eaten.”  They indeed may have been
beautiful, green, and lush.  But they
aren’t necessarily healthy if you have to use pesticides, herbicides, and synthetic
fertilizers.  Think about it:  Do you consider people who are dependent on
synthetic medications really healthy?  They
might look well, but are they really?  Why
would plants be any different?

Other than the Bt on the broccoli and cabbage plants early
in the season, I didn’t use any other pesticides.  I don’t think I used any Miracle-Gro this
year, just organic fertilizer that I either purchased at deep discount at the
end of the previous season or made myself (DIY complete organic fertilizer,
link below).  I learned from my neighbor
Terri that she lost many of her vegetables to aphids, thus trashing my theory
that the harsh winter had eliminated them.

So what happened?

Plant diversity, as I learned in the boot camp class.  Most of us are familiar with the three sisters
planting the Native Americans practiced: 
Corn stalks supported beans, and the beans help anchor the corn from the
wind.  Beans fix nitrogen that fertilizes
the corn.  Squash shade the ground,
preventing weeds and conserving water. 
The squash vines also hampered deer and raccoons from raiding the
garden.  Sunflowers were also
incorporated, serving as a windbreak and attracting pollinators. 

Those four plants come from four different plant families,
which researchers have found is the minimum number needed for plants to be
healthy for people and repellent to pests. 
Having six different families in close proximity is good.  Having eight is even better. 

And that’s what I had this past year throughout my garden,
except in the very beginning when only the cabbage and broccoli (which are in
the same family, of course) were growing. 

The purpose of discussing planting diversity in the garden to
eliminate pests isn’t to persuade readers to grow stealth gardens with
everything mixed together.  I’ll be the
first to say that it isn’t all that efficient. 
It takes a bit more work.  But as
Mr. DeMille shared in his class, a few large-scale producers are adopting this
practice as well.  It’s totally possible
to interplant rows of tomatoes with carrots and basil, perhaps throw in some
onions, and then some low-growing flowers like alyssum or pansies.  If I had the space, this is what I would
do. 

In planning the garden this year, to take even more advantage of
the perks of plant diversity, I needed to know what veggies, fruits, and
flowers belong to which families, which are a step above species and genus in
plant classification.  We all know that
tomatoes, peppers, and potatoes are in the same family, but did you know that
petunias are also a nightshade?  I didn’t.  Or that sweet potatoes are not a nightshade,
but in the same family with morning glory? 
I don’t see the family resemblance, either. 

This is just a start; there are so many more plant families
and representatives that could be added to the garden.  I don’t know if I would have believed that
diversity in planting the garden could reduce or eliminate a pest problem in
the fruits and vegetables if I hadn’t seen it myself.  Having seen it, I will never go back.  I just need to do a little more planning is
all, the this chart will help me.

Links to related
posts:

Stealth
Gardening:  Hiding Your Garden in Plain Sight  

Using Nasturtiums to Protect Cabbage and Broccoli

Carrots Love Tomatoes Book Review (Companion planting) 

Complete Organic Fertilizer 

Fruit tree guilds  

References:

https://www.thegeorgicrevolution.com/general-clean

https://www.thegeorgicrevolution.com/technology

https://ucanr.edu/sites/placernevadasmallfarms/files/170644.pdf

https://www.gardeningknowhow.com/edible/vegetables/vgen/different-vegetable-families.htm

https://www.fondation-louisbonduelle.org/en/my-vegetable-garden/grouping-vegetables-according-to-plant-families/

The Vegetable Families: Who’s Who in the Vegetable Garden