Science-based companion planting

Buy your own copy of Plant Partners
by Jessica Walliser at Amazon.

Much has been written about which plants work well together, and often the various human emotions, such as love and hate, accompany these descriptions. Extension agents, university professors, and other scientists had debunked most of the anecdotal benefits of traditional companion planting. 

But now there is new science on using various plants to:
- act as trap crops to lure pests away from crops,
- attract predatory insects that will reduce pest problems on crops,
- add diversity, which may confuse pest organisms.
- reduce weeds,
- increase pollinator populations,
- add nutrients, and more.

Jessica Walliser's new book, "Plant  Partners: Science-Based Companion Strategies for the Vegetable Garden" (published by Storey Publishing) is the winner of a 2021 The American Horticultural Society Book Award. Jessica is a rare two-time winner of this prestigious award and her book compiles this latest research on using plants to accomplish several benefits in vegetable gardens. 

Smart Gardening

Let's combat those horticultural myths with science 

This meme with a reminder to share
about male and female pepper fruits based on
 the number of lobes is total baloney!

The Internet has been a fantastic tool for sharing all of human knowledge. Social media, powered via the Internet, has made it easier to reconnect with long-lost friends and relatives and to share photos and memes with the world. It also serves as a market place, with online shopping.

But all this mostly unfiltered access to eye balls has made it ripe for spreading misleading information and blatant misinformation. Plus, this unfiltered marketplace allows for the selling of ineffective or bogus products with no chance for returns.

But, our topic is gardening and landscaping, so let's look at a few examples of bad information so widely shared that those myths have become accepted as fact.

Soap destroys plants' defenses

How to fight aphids on milkweed?

We plant milkweeds to encourage the monarch butterflies, not only for the nectar, but also because milkweed is the ONLY larval food for the monarch caterpillars. But milkweed also attracts aphids...

Non-native scarlet milkweed (Asclepias curassavica)*. Notice all the yellow aphids on the stems.

I was focused on the monarch when I took the above photo, but it's obvious that my milkweeds had become infested with aphids. I just allowed the aphids to stay. Eventually some ladybugs came in, but the plant is better off without any "treatment" from the gardener.

Often the "expert" advice is to spray homemade concoctions with soap or detergent to get rid of the aphids. Don't do it! 

A failed onion crop

My onions failed to form bulbs. Were they a long-day variety?

I've had some wonderful onion harvests in the past, but not this year. See my post A sweet onion harvest to see what a successful onion crop looks like. Note: that crop was harvested in May.

So what happened? 

Well, I was distracted this fall with my #floweredshirttour for my third book, The Art of Maintaining a Florida Native Landscape—35 events in 11 weeks from September 1 to November 15th. Instead of taking the time to order my short-day onion plants, I just bought a package of onion sets, which I'd used before, with reasonable success. See my post, The skinny on onions, back when I was just figuring out what to do in Florida. The information I found at the time said that only short-day onions, which is what we need in Florida because we grow onions through the winter, were available as sets.

After the #FloweredShirtTour

I was leaving for a multi-day trip
at sunrise with my 3 flowered shirts.

"The Art of  Maintaining a
Florida Native Landscape"

I named my latest 11-week book tour (Sept. 1 to Nov. 10) the #FloweredShirtTour. My third book, "The Art of Maintaining a Florida Native Landscape," was published by University Press of Florida in September. Back in May I was a speaker at the Florida Native Plant Society (FNPS) conference and at the end of my talk, I held up my calendar and asked the audience to fill up my dance card. Did they ever!

I sent emails to the contacts on all the chapters' websites and had also arranged to hold an all-day workshop of the chapters on outreach in September. In addition I'd contacted other groups that hold events in the fall and asked to be on their programs. All in all, I ended up with 35 events in 11 weeks. I've documented most of the events on my Appearances Page.

Nematodes, marigolds, and crop rotation

Marigolds as a cover crop: they are not only useful, but also beautiful and
attract butterflies and bees.

This summer, for several reasons, I skipped most of the summer crops and planted a cover crop of marigolds. I'd also planted a lot of marigolds around the tomatoes earlier in the season--about 3 marigolds for every tomato plant.

This is my experiment to see if I can reduce the root-knot nematode populations in my gardens.

First, as I've been preaching in my talks, just planting marigolds around the tomatoes does not prevent nematode damage. Here is the result...

Old gardeners' tales

Old gardeners' tales are rampant, even these days.

Companion planting advice as shown in this graphic is freely passed along as gospel of the garden. But most of the companion planting pairings (compatible or incompatible) have not been verified with scientific methods.  Nevertheless, books have been written about plants with human emotions such as "love" or "hate" used in their titles.
  
Don't fall for these old gardeners' tales.

In my research for "Organic Methods for Vegetable Gardening in Florida," I found that the more important thing to keep in mind is the botanical family of the plants so your crop rotation from one season to the next includes different crop families for at least two rounds. This keeps the specific pests guessing and allows the soils to be replenished.

One of my go to resources for garden myths is Linda Chalker-Scott's website, The Informed Gardener. She's an urban extension agent in Washington State and she has access to the professional journals where she researches various gardening traditions to find if the science proves them to be true or not. She's also published two books listing some of the most common myths.