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. 

 

Family	Vegetable	Fruit and Flower
Asteraceae	artichoke, tarragon, lettuce, salsify	calendula, zinnia, marigold, sunflower, artemisia, chrysanthemum, chamomile, dandelion
Brassicaceae	cabbage, broccoli, Brussels sprouts, cauliflower, pak choi, radishes, kale, kohlrabi, turnips, collard greens,	sweet alyssum
Chenopodiaceae	Swiss chard, beets, and spinach, amaranth, quinoa, lamb’s quarter
Convolvulaceae	sweet potato	morning glory, bindweed
Cucurbitaceae	summer and winter squashes, cucumbers, melons.
Fabaceae	beans, peas, peanuts, cowpeas, clover, alfalfa, lentils, soy, fava beans	lupine
Lamiaceae	peppermint, spearmint, catmint, lemon balm, rosemary, oregano, thyme, sage, lavender, basil, marjoram,
Liliaceae	onions/garlic, shallots, chives, asparagus, leeks	lilies
Malvaceae	okra	mallow, hollyhock
Poaceae	corn, rice, wheat millet
Rosaceae		strawberries, cherries, raspberries, blackberries, pears, apples, peaches, apricots, almonds, plums roses
Solanaceae	tomatoes, peppers, eggplant, potatoes	petunia
Umbelliferae	carrots, caraway, celery, chervil, cilantro, cumin, fennel, parsnips, parsley, dill
Violaceae		pansy, johnny jump up,

 

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, and 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/

http://vegetablegardenhub.com/vegetable-families