Sunday, September 10, 2017

Cheyenne Botanic: Down and Dirty

Day two of the Cheyenne Botanic Crevice Garden, folks.
It's helpful to play a bit with some rocks to get a feel of how they relate, so I made a maquette one night next to the rock pile.

Before rocks comes the base layer and below-grade excavation of soil.  Where stones will be set deeper than the original earth, we dug with a mini excavator, and piled that up where the greatest elevation will be. And added more soil.

We brought in two small dumptrucks of a word I've grown to loathe.  "Topsoil." I hate it because it means just about nothing to anyone.  There is a real definition, but folks in the industry call whatever they want to claim is good for growing plants as "topsoil."  Whatever.

This stuff is a mature, humate-laced soil, made of silty loam, but screened from sod and displaced soil, so it has very fine, incorporated organic material.  It pretty well matches what exists on the site, which is just a little compacted.  It was recycled by the City of Cheyenne.

Later, there will be a 12-8" layer on top of the most recent iteration of artificial soil mixes. The fancy stuff.  But here is what is different this time, based on the performance of the crevice gardens at KAFM and APEX:  The fancy stuff will not be too deep; a heavier, decent, original soil will be within an easier reach of plants. A "topsoil."  

In the past, I've had up to a few feet deep (as much as possible!) of a very light, free-draining mix over heavy clay. 
This time, the light mix is just a bit heavier, with more expanded shale and a small amount of compost, and not as deep, giving newly rooting plants a shorter race to establishment in the heavier soil. And that heavier bottom layer is sandy silt this time- two steps lighter than clay.   We are not growing just saxatile and mineral-loving alpines or desert plants, which would resent organic material.  

To sum it up about our this two-layer soil system: Both soils will be a little more similar to one another, and more balanced in proportion, compared to the past.

Whew. After working out all that, and visualizing the general shape of the thing, while accumulating the ingredients for the soilmix on the side, it's finally time to set the first stones.

We've got 5.

With big crevices.

Big crevices.  Biiig.  Let's have shrubs in this crevice garden.

Oh?  You want the recipe of the new soil mix?  Try it at your own risk.  Proportions are a good guess.
3 pt SAND - Coarse masonry/concrete/builder's
2 pt EXPANDED SHALE- (fine: 1/8" and down or 1/8-1/4" works)
1 pt SCORIA- (this is screened 1/4" from Paulino's Gardens in North Denver. You could use fine, too.
1/3 pt COMPOST- well aged, finer screened (to avoid big chunks which will collapse upon breaking down and settle) {Yeah, I know you aren't supposed to use fractions for a recipe in "parts!" We'll see how it changes the outcome.}

The scoria. (red)
All of the Crevice Garden new mix:
Expanded shale (in sacks), the scoria, the sand, and sand + compost in dump-truck

The final mix does not sit there quite like sand; it is more stable.

And cakes a little.  I hope the plants like our sand cakes.

I'll let you know how it goes.


Bobby La said...

And so it begins....I have done a lot of stonework in my time Seth, no crevice gardens though I am attempting one at the moment, but if there is one adage that applies to any job I've ever done with masonry it's "good stonework takes time". There's a few others that are worth keeping in mind, but the other one I cast before the newbs is "it takes as long to lay a small rock as it does a big one". Good luck on the project, love your work.

Cheers Ross (not Bobby La - using my partners account)

David Cristiani said...

This is going to be good...I'm already picturing the whole section by the initial rocks and the curve of the building...