Mr. Sellars and the Great Distinction

In Vancouver, there were many pleasures.  One of the longest-lived was time with a stalwart contributor to North American Rock Gardening, Mr. David Sellars and his wife Wendy. She spoiled me with tea.  It was a stuggle to leave.

Many super details about plant cultivation came into conversations while we visited, but a great theme stood out to me as being incredibly useful for all of us gardeners to wrap our heads around- especially those of us interested in growing wild plants like alpines, rock-lovers (saxicoles), or dry-lovers (xerophytes) and your everyday garden plants.

A great distinction must happen in our gardens if we want to accomodate them.

David thinks in terms of a great divorce in soil. (A quick C. S. Lewis reference, thank you)

"Sand" versus "Meadow"
These are his personal pragmatic terms.  We could also refer to these as
"Mineral" versus "Composty"
or, maybe
"Poor" (but well-drained, dangit) and "Rich" (and still well-drained, dangit.)

This is within the world of rock gardens, where most plants want "good drainage," which is to say, that water will not sit in the soil, it will never be boggy, but metabolically, the plant's roots will not drown because there will always be oxygen in the soil.  Oh, recall that horribly elusive description of conditions desired by the plants you desire: "Moist but well-drained."    Your plant is Goldilocks, and she just wants water all the time, but with air, too.  Our great efforts over the years to make ways of making this possible, in the absence of eroded mountainside in our back yards- this has lead us to finding that even if we acheive great drainage- we are not done.  There is one more thing our plants ask for.

French-fries versus Sweet-potato fries.  {I noticed that Canada has been taken hostage by an addiction to Sweet Potato Fries served with Chipotle-Mayo; it was offered everywhere; no kidding.

Well, the same is true of plants- it is a matter of preference, and moreso for plants- based on where one hails from.

What David was talking about was providing at least two distinct kinds of rock garden soil in the garden, leaving a person the chance to accomodate plants in either, because the fact is that many of us are trying to grow a great deal of plants who have wildy different preferences.

What does Sand/Mineral/Poor mean?  For many experiences rock gardeners, this means a flower bed that is made up of sand, top-dressed with a layer of gravel, rock, or totally paved with stones in the case of Czech crevice gardens.  The Swedish wildman Peter Korn shocks all of his listeners by revealing his secret of succes:  Just sand. David uses something local called "Sechelt Sand"  which is part regular sand and crusher fines, (called "breeze" in much of Colorado, and other things elsewhere like "rock dust" in the UK- it is just the dust and finest gritty stuff left over from crushing rock into gravels), giving some fine texture and mineral nutrients, some coarse texture, and a lot of in-between, but with no compost, no black rick humus, no worms, none of that vegetable-garden-gold.
A gardener you'll meet in a later post in detail, Stephanie, and whose garden is a massive essay in the reality of plants who prefer mineral soil, uses half gravel and half sand. (I am leaning this way myself).

My desert crevice garden is in the mineral camp: an "unamended" (and therefore lacking composts, etc) sandy loam, which is a naturally occuring local thing, which happens to be comprised of 91% fine sand and 9% clay.  It's decomposed rock without any years of falling leaves worked in.

What about Meadow/Organic/Rich? This can be lots of things (like David's home-made leafmould, above).  It may be the garden's original soil, with years of rich amendmens (composts, manures) which is elevated in a bed, perhaps, or amended with gravel to create the desired drainage.  This soil has more in common with the traditional flower-garden soil. But what is always true is that there are lots of dead things (plant materials like decomposed wood, leaves, dung) and also lots of living things like worms, nematodes, mycorhizae, insects, and countless microorganisms at work in the soil.  This would be fine to accomodate Vegetable plants, indeed.  But this soil, if we meant to grow rock garden plants in it, would need drainage which may not be as important to something like a tomato plant.

Why on earth would we want the first one? Mineral, inorganic, poor soils?

Castilleja hispida and Penstemon davidsonii, in BC.

It seems some plants prefer it.  It seems lots of plants prefer it.
In fact, a great deal of the plants which interest the plant-collecting or rock-garden gardener, tired of the run-of-the-mill species, seem to only succeed in mineral soils.  Some folks make conjecture that these "new" soils, as they'd be called in a natural setting, are  preferred by many Penstemons, Prickly Poppies (Argemone), Blazingstars (Mentzelia), Milkvetches(Astragalus), Buckwheats (Eriogonum) and Indian Paintbrush (Castilleja) because these plants, like introverts at a big party, don't like the company of all the living stuff in the soil.  They want to be alone in the rough stuff.

It is quite paradoxical that all that life in a rich soil may be just as bad for some plants as it is good to others.  This balance and interplay may explain the mysterious presence and absence of any species in any place on the planet through fathoms of as-yet-understood science.

Crazy, yes.
But brilliant.

But back to us gardeners:

Essentially, we are clever party-hosts conspiring to cook two different meals so we can invite a wider range of guests to our garden biodiversity party.  It's like having Bratwusts and Vegetarian on hand at once.

Perhaps those special desert-dwelling or mountain-side plants should be thought of metaphorically as vegetarians, not fond of the over-rich diet of other garden plants.

Here is what David's "vegetarian buffet," looks like.  Certain plants which could not make it elsewhere are thriving here in his Tufa stone over sechelt-sand.

Wonderfully, the name "Saxifrage",  or genus "Saxifraga" means "rock breaker," because Saxes grow in tight fissures and cracks in nature, appearing to be trying to pry the stone apart.  Positioned  in this way in their natural places, no wonder they don't like regular garden soil!

 Some gardens are a sneaky mix of both- some sections and pockets between rocks are rich, others are sand.

Here is the literal line in David's garden, betrayed by the plants visible above-ground. Rock-loving plants on the left, and humus-loving Dactylorhiza foliosa on the right.

Lastly, the implication arises that in nature, there is a wide and complete spectrum between the two, and  some plants obviously grow in-between, which means that every plant's needs are relative, and great gardneers indeed go to great lengths in one way or another to provide as much of this spectrum as possible for the greatest range of plants. I'd like to surmise that this means that if our regular garden soil tends toward one or the other, and a plant is adament about being dead in that soil, that to provide the opposite might just be the ticket.

There are also, of course, lots of plants who go both ways.  This seems true of the "main-stream" rock-garden classic plants.

What is more, the spectrum will work differently in different climates.

And after-lasty, I want to mention for the most engaged of readers, that I experimented with treating potting-mixes and seedling-mixes in this way, which seems to have coincided with sudden success with  the likes of Arbutus xalapensis, Caesalpinia repens, Castilleja linariafolia, Schrankia sp.,  all of whom have consistently met their deaths in my hands in the past.

Of course, this begs a roll-call example of plants in these distinctions, plants which give a nod to David Sellar's garden.  I invite readers to correct and add plants to a list.

The Sand/Mineral Team:
Lewisia sp.
Eriogonum sp.
Castilleja sp. (I believe)
Penstemon sp.
Petrophyton sp.

The Rich Meadow Team:
Ground Orchids
Trillium sp.
Gentiana sp.

Either-One-is-Fine-Thanks Team:
Daphne sp, in general.
Erigeron sp.
Draba sp.
Globularia sp.
Acantholimon sp.

Let us take another look at our plants and ask them
"Just what do you want?"