Science-Based Gardening Making a Comeback?


Constance Casey, the most excellent garden writer at, makes the case in her latest column for the Science of Gardening, citing the work of Friends-of-Rant Jeff Gillman and Linda Chalker-Scott.  Required reading for anyone out there unfamiliar with these two outstanding researchers. 

Long-time readers may remember my taking issue with the so-called "gardening information" promulgated by certain wildlife advocacy groups or my rants about the folksy but rich gardening quack Jerry Baker.  Well, Gillman, Chalker-Scott and Casey herself are all on the side of old-fashioned, objective science – yay!!

Coming soon from Jeff are his quarterly updates on Hot Topics in Research for  But don’t worry; I’ll post about it here, too.


  1. Loved all the articles, though I am shocked to learn that a) I need to go dig up all my irises, antique climbing roses, daylilies, artemesia, lavender, etc., if I am going to have a “true” xeriscape, and b) I’m suppose to spray stuff with a strange concoction. As far as the latter goes, sounds like a lot of work, and I don’t think anything actually seems to need spraying…

  2. And what is wrong with Jerry Faker — I mean Baker?

    Come on. Get a life! Everyone should know that to have a successful garden you must pee in your blender.

  3. I’m of two minds about the articles. On the one hand, I also dislike the on-size-fits-all you must do XYZ approach of some organizations. On the other hand, there’s strong scientific evidence that more natives in the garden supports a bird population that can actually breed. “Bringing Nature Home” has a lot of scientific evidence for that. Same with cutting root balls. For many plants, that works well. But a lot of California natives and some other plants (e.g. bougainvillea) have brittle roots that must be handled gently.
    When scientific results are picked up and repeated, part of the information often gets lost. So, I’m in favor of the scientific approach, but…

  4. Renate, I think we’re in agreement. In fact, when I reviewed Tallamy’s book I said he made the absolute best case for native plants – because he relied on science, and because providing for wildlife is such a compelling argument.

  5. Curious about the eggshell slug experiement. I did the same in my own garden. I encircled some bok choy with shells; others without. The ones that were encircled were left alone. The others were slimed to the ground. As Renate says, “I’m in favor of the scientific approach, but…”

  6. Casey and the authors she discusses seem to be arguing against a straw man. Who pours beer on their plant to make it flower? Or sprays their plant with whisky to kill bugs? Maybe I don’t hang around the “right” gardeners?

  7. Disregard my last comment, I just read your post on Jerry Baker. I am pretty sure the “spring cleanup spray” he recommend would be considered illegal polluting if it came out of a factory’s smoke stack. Definitely niiiice and green.

    I can’t believe public money and donations are paying for such a nut to be on TV.

  8. Gardenmentor

    I like your attitude (ie I’m in favor of the scientific approach but…). Science doesn’t always get it right (our experiments are often too contrived to give a perfect answer) — but I feel pretty confident about the egg shells — I’ve met enough people who have had egg shells fail to stop slugs (including myself) that I’m confident that they’re not a great barrier to slugs. What you set up was a “choice” experiment. In other words the slugs could “choose” to go to a plant with or without eggshells without expending too much effort. In those types of experiments even minor deterrents can work — because the slug has a better place to go!

  9. I have a problem with one bit of Ms. Casey’s “science says” advice, and that is when it comes to planting a tree.

    If the soil you dig up at planting time is absolute junk, crappy, inert, lifeless junk, lacking organic matter or consisting of heavy clay, you’d be a fool not to amend the soil when you shovel it back in. Too many top university tree experts I trust (Gary Johnson at the U of MN, for one) have told me that amending the soil when planting a tree is advisable under these conditions.

    In these cases, yeah, you want a huge hole, big as possible, six-foot diameter is nice. I also advise an old Norwegian tree-planting technique of hacking out five or six spokes that travel straight out from the primary hole, a foot or so deep, and filling these troughs with amended soil (for secondary and tertiary roots to find in years ahead, rather than circling in the amended soil).

    Jeff G., you still out there on this one? Thoughts?

  10. Hi Don,

    Yep, I’m still here — and I agree with you. I’m a huge fan of Linda Chalker-Scotts, but I do admit that I have a real problem with her suggestions for tree planting — not only the amendments (and I do think that most of the time it’s not a good idea to amend…but sometimes….) but also the idea of washing off a rootball before planting. I run a nine-acre nursery here at the University of Minnesota, and we’ve tried doing that a number of times — and unless you’re dealing with a small or very easy to transplant tree – like a redbud — the result is death of the planted tree.

  11. Don and Jeff, I’ve always had the same question about the advice to not amend planting soil – what about when the “soil” is crap, especially “builder’s topsoil”?

    So like most everything in g’ing, it depends.

  12. As I said above, when the soil is crap, amend it. I guess by “crap” I mean that it’s obvious it lacks organic matter, not even five percent. This would be your hardpack shales, gravelly gook, high sand percentage soils, heavy clay soils–if the soil is very hard to dig, and if what you do dig are big, hard, solid clumps, toss them in batches into the wheelbarrow, spread some compost over it, chop it up fairly fine, and use that to fill the planting hole.

    Sometimes I’ll just spread out the dirt pile a little bit, shovel compost all over it, hit it with the rototiller, then shovel that mix back into the hole.

    The walls of that hole will be the same, hard, crappy junk, so that’s the reason for the Norwegian spoke concept I mention. In addition, you can loosen up the sides of the hole with a pickaxe (before you place the tree) so that as roots move outward they find indentations, cracks in the wall, in which to grow.

    Sometimes I will spread organic matter, about a six-inch layer, in a two- or three-foot wide circle starting from the edge of the planting hole, then rototill it in a good eight inches. Again, you are loosening the “soil” and introducing organic matter for the secondary and tertiary roots, the feeder roots, that will develop over time. These are not deep anchor roots that hold the tree up, these are roots than will only ever be eight to two inches deep and that grow outward from the tree.

    The point of amending poor soils, by the way, is that if you judge that the soil around the tree contains very little organic matter (or, better yet, a university soil lab test confirms this), adding organic matter is essential to feeding the growth of mycorrhizal fungi on the roots. If you don’t get this fungal growth, the tree has all sorts of problems taking up neutrients, among other handicaps.

    “Builder’s topsoil,” as you know, runs the gamut from gravelly clay left over from the excavation to worse!

Comments are closed.