SEEKING TRUTHS
(The following is adapted from my most recent book, The Ever Curious Gardener: Using a Little Natural Science for a Much Better Garden, available from the usual outlets or, signed, from here.)
OBSERVE AND ASK
Charles Darwin did some of his best work lying on his belly in a grassy meadow. Not daydreaming, but closely observing the lives and work of earthworms, eventually leading to the publication of his final book, The Formation of Vegetable Mould through the Action of Worms. He calculated that these (to some humans) lowly creatures brought 18 tons of nutrient-rich castings to the surface per acre per year, in so doing tilling and aerating the soil while rendering the nutrients more accessible for plant use.
We gardeners can also take a more scientific perspective in our gardens without the need for digital readouts, flashing LEDs, spiraling coils of copper tubing, or other bells and whistles of modern science. What’s most needed is careful observation, an eye out for serendipity, and objectivity.
Observation invites questions. How many tons of castings would Darwin’s earthworms have brought to the surface of the ground in a different soil? Or from soil beneath a forest of trees rather than a grassy meadow?
And questions invite hypotheses, based on what was observed and what is known. Darwin’s prone observations, along with knowledge of soils, earthworms, plants, and climate, might invite a hypothesis such as “Earthworms would bring a greater amount of castings to the surface in a warmer climate.” Is this true? How can we find out?
MAKE A HYPOTHESIS
Gardens are variable and complex ecosystems, which makes growing plants both interesting and, if you want to know why a plant did what it did, frustrating. Many gardeners do something — spraying compost tea on tomatoes to reduce disease, for example — and attribute whatever happens in the ensuing season to the compost tea, ignoring the something else, or combination of things, that might also have made contributions to whatever happened.
Enter the scientific method, a way to test a hypothesis. You put together a hypothesis by drawing on what is known and what can be surmised. In spraying compost tea, your hypothesis, could be based perhaps on the idea that beneficial microbes in compost tea could could fight off pathogens, just as they do in the soil. (Many gardeners do, in fact, recommend compost tea for plant health. Do I? See https://leereich.com/2015/03/compost-tea-snake-oil-or-plant-elixir.html.)
Less disease on your sprayed plants would strengthen the case for further study. Why further study? Because the response of plants in a given season at a given location is not sufficient to make a general recommendation or make a theory.
The way to truly assess the benefit of the spray is to subject it to scientific scrutiny: Come up with a hypothesis, such as “Compost tea reduces tomato leaf diseases,” and then design an experiment to accurately test the validity of the hypothesis.
DESIGN AN EXPERIMENT
A well-designed experiment would need more than just one treated (compost tea sprayed) plant and one control (water sprayed) plant. Grow ten tomato plants of the same variety under the same conditions and some will grow a little more than the others, some a little less. With too few test plants, natural variation in growth from plant to plant might overwhelm any variation due to a treatment (spraying with the tea in this example). Given enough plants to even out the natural variations in, say, disease incidence, the effects of a treatment can be parsed out. Greater natural variations would require more plants for the test.
A garden experiment might have additional sources of variation. Perhaps one side of your garden is more windy, or the soil is slightly different, or basks plants in a bit more sunlight than the other side. Rather than have all the treated plants cozied together growing better or worse because of this added effect, even out these effects by randomizing the locations of treated and control plants.
Now we’ve got an experiment! All that’s needed is to spray designated plants with either the compost tea or the water, and then take measurements. Plug those measurements into a software program for statistical analysis and a computer will spew out a percent probability, based on variability within and between each group of plants, that the tea was responsible for less disease. A test with 90% or 95% probability is usually considered sufficient to link cause and effect. You can then answer “yea” or “nay” to the hypothesized question; you now have a theory, or not.
IS IT SIGNIFICANT?
A good test could involve a lot of plants and a lot of measurements, more than most of us gardeners are willing to endure. A danger exists, as Charles Dudley Warner so aptly put it in his 1870 book, My Summer in a Garden: “I have seen gardens which were all experiment, given over to every new thing, and which produced little or nothing to the owners, except the pleasure of expectation.” Then again, setting up something less than a full-blown experiment could be fun and, while not proving something to a 95% confidence level, still suggest a possible benefit.
Knowing what’s involved in testing a hypothesis also increases appreciation for all that can affect plants. Perhaps your tomato plants’ vibrant health wasn’t from your compost spray. Knowing something of the scientific method can help you assess, whether observed in your own garden or a friend’s garden, or reported in a scientific journal, the benefit of the spray.
So go out to your garden and look more deeply into Nature, perhaps, like Darwin, lying on your belly. Understanding some of the science at play in the garden takes it to the next level. And you’ll find that the real world, neatly woven together, is imbued with its own poetry, with science being one window into that poetry.
Me mulching, even as a beginning gardener
I guess two plants per pole, with poles about a foot apart, is too crowded. Next year: one plant per pole.
A close eye is needed on cabbage and its kin because one day there’ll be no damage and next time you look, leaves are riddled with holes and poop.
Occasional, light sprinklings of soil add bulk to the finished mix. Occasional, sprinklings of ground limestone keep planted ground, final stop for the compost, in the right pH range.
I train my tomato plants to stakes and single stems, which allows me to set plants only 18 inches apart and harvest lots of fruit by utilizing the third dimension: up. At least weekly, I snap (if early morning, when shoots are turgid) or prune (later in the day, when shoots are flaccid) off all suckers and tie the main stems to their metal conduit supports.
I lop wayward shoots either right back to their origin or, in hope of their forming “spurs” on which will hang future fruits, back to the whorl of leaves near the bases of the shoots.
Newly planted trees and shrubs are another story. This first year, while their roots are spreading out in the ground, is critical for them. I make a list of these plants each spring and then water them weekly by hand all summer long unless the skies do the job for me (as measured in a rain gauge because what seems like a heavy rainfall often has dropped surprisingly little water).
Not only vegetables get this treatment. Buy a packet of seeds of delphinium, pinks, or some other perennial, sow them now, overwinter them in a cool place with good light, or a cold (but not too cold) place with very little light, and the result is enough plants for a sweeping field of blue or pink next year. Sown in the spring, they won’t bloom until their second season even though they’ll need lots of space that whole first season.
Every time I look at a weed, I’m thinking how it’s either sending roots further afield underground or is flowering (or will flower) to scatter its seed. Much of gardening isn’t about the here and now, so I also weed now for less weeds next season. It’s worth it.
They’ve been making headway across the Northeast since arriving in Cambridge, Massachusetts in 1992. But my lilies still look fine and, yes, I do still see some of those beetles. Perhaps one of the natural predators released in Rhode Island years ago has joined the crowd here, minimizing damage.
Then, about 10 years later, and since then, they’ve showed up on schedule, which is now, but then disappeared for the rest of the season. Did they go off to greener pastures? Did they succumb to soil nematodes or fungi?
Although chemical, mechanical, and biological controls are still under development, this pest has not put an end to my blueberry-eating days. Thanks to some bait and kill traps developed by Cornell’s Peter Jentsch, damage has been kept to a minimum.
To make matters worse, it also exudes a sticky honeydew which falls on any nearby surface (other leaves, lawn furniture, etc.) and, worse yet, becomes food for a fungus than turns that stickiness dark.
In spring, nymphs hatch and climb trees in search of soft, new growth. The one-inch long adults emerge around now; they’re very mobile, usually jumping but also capable of flying, which is when their spread wings display their bright red color. With wings folded, the insects are mostly gray wings with dark spots.
A few natural predators, such as spiders and praying mantises, feast on SLF, but not enough. What to do? There are a few approaches.
This ancient variety, elongated and with a black skin, has been grown almost exclusively near the Pardailhan region of France. Why am I growing it? The flavor is allegedly sweeter than most turnips, reminiscent of hazelnut or chestnut.
Next year I can expect a vine growing 6 to 9 feet high and which is both decorative and tolerates some shade. What’s not to like? (I’ll report back with the flavor.)
Later in the season, cluster of bulbs form, similar to shallots, although forming larger bulbs. They can overwinter and make new onion greens and bulbs the following years.
The problem was separating the small tubers from soil and small stones. I have a plan this time around — more about this at harvest time.