(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.)


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.
Darwin and worms
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? 


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

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. 


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. 
Variability in plant populations
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. 
Experimental design
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. 


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

Me mulching, even as a beginning gardener


More Citrus in the Making

You wouldn’t think that a couple of small, green sprouts could elicit so much excitement. Especially this time of year, with vigorous, green shoots sprouting up all over the place. But they did, in me. Not that anyone else would notice the two sprouts.
    The sprouts were from grafts I made a couple of months ago. Over the years I’ve done hundreds of successful grafts; these two were special.
    The first was citrus, special because the trees are subtropical and evergreen. The many apples, pears, and plums that I’ve grafted over the years are deciduous. I graft them when they are leafless and just about ready to start growing. Because the grafts are leafless, the wood, as long as the graft union is sealed, won’t dry out.
    Not so for citrus, more specifically for the stems I clipped off my potted Golden Nugget tangerine tree. What was needed, then was a rootstock on which to graft that stem. The result would be a Golden Nugget plant above the graft (which stays right where it is no matter how much the plant grows). Clipping all the leaves from the stem forestalled moisture loss.
    My home is also home to kumquat, another citrus that lives in a pot here, outdoors in summer and in a sunny window in winter. A couple of February’s ago, I glanced down at the kumquat seeds I had just spit out from fruits I harvested and ate. Not being able to squander their potential, I planted them in pots. A decade might have gone by before they were old enough to bear fruit but, after two years, the pencil-thick stems were large enough for grafting.

Citrus graft, a success

Citrus graft, a success

   With kumquat rootstocks poised for the operation and Golden Nugget scions (the stem to be grafted atop the rootstock) stripped of leaves and also ready, the procedure was the same as for apple trees and other deciduous plants: matching, sloping cuts on rootstock and scion held in place by a wrapping with a rubber strip; covering the wound to prevent moisture loss. My usual choice of covering is Tree-Kote, which gets painted on, or Parafilm, a stretchy film that adheres to itself.
    The citrus scion was fleshy enough to also lose moisture right through the bark. To prevent this, I wrapped the whole scion in the Parafilm. A blackened scion had followed previous attempts at grafting citrus without wrapping the stem.
    A week or so ago, it was time to unwrap the Parafilm from around the stem. If the grafted parts were going to knit together, they should have done so by then. Lo and behold, a small, green sprout soon pushed out from the top bud of the scion.

 Nutty Grafting

    Not all deciduous trees are as easy to graft as apple and pear. Nut trees in the Juglandaceae family, which includes black walnuts, English walnuts, butternuts, pecans, and hickories, are notoriously difficult. Part of the reason is because cutting a stem in spring, which is, of course, unavoidable when grafting, makes these trees bleed, messing up the works.
    With a slew of failures at grafting this family under my belt, I needed to try again. The candidate this year was a nut tree called buartnut, and hybrid tree with a hybrid name, the latter a non-euphonious combination of the words “heartnut” and “butternut.” Heartnut is a Japanese species of walnut, notable mostly for how easily it cracks to yield two heart-shaped nutmeats. Butternut is a richly flavored nut borne on a native tree that is becoming increasingly rare because of a blight disease.
    Buartnuts allegedly need cross-pollination to bear nuts. My tree, large and spreading though only about 15 years old, lacked a mate. The mate needn’t be a whole other tree; a branch from another tree, grafted on my tree, would suffice and avoid the need to plant a whole new tree or wait the years it would take to flower. Grafted branches bear much more quickly than new trees.
    Fortunately, I knew of another buartnut tree that could provide pollination. Last winter, I clipped off a few of its stems, packed them in a plastic bag, wrapped the bag in a wet towel, and then packed that whole mess into another plastic bag and then into the refrigerator. There, they remained hydrated and dormant until needed.

Heartnut graft, one sprout

Heartnut graft, one sprout

    The key, I’ve been told, to grafting Juglandaceae, is to wait in spring until a spate of 80 degree plus weather is predicted. Conditions seemed right on a day last May. Because of past failures, I attempted numerous grafts, three different kinds: the bark graft, the banana graft, and the whip graft. To promote bleeding off-site rather than at the grafts, I slit stems below the grafts. I covered one of the bark grafts with a plastic bag and then, for shade so the stems wouldn’t cook, a paper bag.
    Almost all the grafts failed. Except one. Just one stem of just one of the bark grafts (each of these bark grafts carries 4 or 5 stems) sprouted. How exciting!

Temple Disruption

    Exciting goings-on in the blueberry patch also. Birds are flitting about every morning, enjoying a few berries despite our repeated efforts to secure any openings in the walk-in “Blueberry Temple.” I threaded some string to more tightly join the top and side netting. As previously, I think this will solve the problem.
    Then again, this may be a Darwinian experiment. Birds never used to work their way into the Temple. Openings in the top netting are 1” across; I fear the net is breeding for smaller models of cedar waxwings and catbirds. Or perhaps smarter ones better at finagling their way to the blueberries