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.

How NOT to plant a tree!

P.Allen Smith, famous TV gardener,
 demonstrating how NOT to plant a tree.
The burlap should have been removed
and no amendments should have been added.
This is disinformation has been propagated
to make sales for his sponsors.

We have had many examples provided to us with exactly the wrong information for planting a tree. Just plop the whole root ball in the planting hole filled with rich amendments. This may be worse than just misinformation, which implies a mistake, because it's done for the purpose of selling a product. This would be classified as disinformation.

Here is what is the recommended tree planting instructions which have been supported by research and experiments:

- Select younger, un-topped trees with a caliper measure of less than half an inch (the trunk diameter measured at six inches above the soil line) Small trees will adjust much faster and will begin to grow more quickly than older ones held longer in their pots. Protect young saplings for two years or more, tethering them lightly to sturdy stakes.

- For container-grown trees, rinse off all the growing medium and do not add any amendments to the planting hole or the roots could circle around in that rich soil. Roots need to spread out so the tree will be more wind- and drought-tolerant. (For transplants and field grown trees, keep as much of the soil on the roots as possible, but not for containergrown trees.)

- Circling roots need to be corrected so the tree does not girdle itself as it grows.

- Make sure that the real root flare, which is sometimes buried during repotting, is at least an inch or two above the final soil line.

- Mulch new trees with shredded leaves, shredded natural bark mulch, or arborist wood chips to help retain moisture and reduce weeds, but keep mulch several inches away from the trunks. Once trees are established, planting with native ground covers provides a living mulch.

Bad information about leaving the wire basket in place. Bad information about the root flare. But unlike Smith they do advise that the burlap should be untied and they don't mention amendments. 

The results many years later of not rinsing the roots or removing the root ball container. In this case it was plastic orange strings. 

Rinsing the roots it the best way to ensure that they spread out and not continue to coil in the planting medium.

The vast majority of companion planting advice
 is not based on any science-based research. 

Companion planting myths

Most of the advise on companion planting has no science behind it, but some like planting marigolds with tomatoes to reduce root knot nematodes is almost true. Actually, for the marigolds to reduce nematodes, it should be planted densely as a cover crop and dug into the soil or buried under a new layer of compost. I verified this in my yard, but the real science with controlled experiments was carried out at the University of Florida.

Much of the companion plant advice is ineffective at best and detrimental in some cases like the total fiction of planting sunflowers near your cucumbers or even planting sunflowers as a trellis for cucumbers. Sunflowers exude an herbicide from their roots and from all part of the plant. If you've ever had a sunflower seed bird feeder, you probably observed that nothing grows where the sunflower shells fall. This trait is known as allelopathy and other plants such a Australian pines and black walnut do this as well. So the wide-spread advice of planting sunflowers with cucumbers or any other desirable crop is much worse than just ineffective. The cucumbers will suffer and the gardeners following this bad advice will blame themselves--maybe even thinking that they have a "black thumb."

A study on the allelopathy of sunflower.

Bad companion planting advice.

Sunflowers are detrimental to cucumbers.

This vinegar-salt concoction has been widely shared,
but it's not benign. This stuff is poison not only to
 plants, but also to the soil and its beneficial critters.
I've modified this meme as a rebuttal. 

A poison is a poison is a poison

Just because ingredients are organic or are found in our kitchens and are not sold with poisons, it doesn't mean that they can't harm the environment. See my post: A Poison is a Poison is a Poison. 

Home-made weed killers are an attractive idea so we can battle the weeds with something other than Round-Up. Just be aware that these concoctions are still poisonous and quite a bit less effective, as noted on the meme, "You may need to treat stubborn weeds twice." So use with caution. 

Ladybug larvae will consume 100s of aphids and
other sucking bugs and will continue to prey on
them as an adult. But those soapy poisons will
kill this predator and other good bugs. 

There are other homemade remedies made with soap and or alcohol that you can spray to kill aphids and other sucking bugs on your plants. Don't do it, because you'll also kill the aphid predators and many more benign bugs as well. 

In addition, all the soap and/or detergent-based sprays will dissolve the waxy cuticle on the leaves and stems, so the plant will become more susceptible to future bug attacks as well as increased dessication. Read "Soap destroys plants' defenses" for more information on how this happens.  

As far as poisons of any type in the landscape, use with extreme caution and never use landscape-wide poison applications to your lawn or anywhere else and don't spray for mosquitoes. 

Linda Chalker-Scott

Science-based gardening advice

With sooo many sources of bogus gardening information, where can we find reliable, evidence-based scientific advice? One of my frequent sources for science-based advice is Linda Chalker-Scott's website www.informedgardener.com. Dr. Chalker-Scott has researched science journals looking to prove or disprove gardening advice. Her collection of peer-reviewed papers covers horticulture myths on many different topics. For instance, it was shown 100+ years ago that a layer of gravel in the bottom of pots actually impedes drainage, but we can still find TV gardeners and articles that still offer this bad advice.

In addition to her website, many of the myth papers are available in two books, The Informed Gardener and The Informed Gardener Blooms Again.

The Informed Gardener

And on the back cover... Guess who?

So let's all become smarter gardeners.

Green Gardening Matters,
Ginny Stibolt