Monday, May 5, 2014

Spring's a-rockin' along...

Those of us in the "green industry" are really too busy to be online.  Too few daylight hours exist as it is.  And out there in the real world, this spring brings new fun developments in everyone's gardens.  Like some respectable growth on more architectural oddities like Shepherdia rotundifolia, Frankenia jamesii.

Castilleja integra flowers loudly echo the new spines of Agave utahensis var. kaibabensis.

And, a first for me, blooms on Castiellja sessiliflora, bought from Sunscapes rare plant nursery last year.

Here's what I've been busy with.  A 5.5 ton "granite" (Amphibolite) rockery for my friend Jan in Ft. Collins.  My envy is as heavy as the stone.  It was fun to make, but I am totalyl deprived the most fun part:  planting.

Jan will execute that herself with stunning artisticality, I am sure.  When they are new, a crevice garden looks like a bare sore on the landscape, just calling, howling to have plants in it.  I feel the void that nature must ache from until the gardener breaks out the dandelion-digger (now rockery-planter) and flats of rock-garden plants.

That's it.  It's gone too far.  I can't even count sheep when I'm in bed
(or walking through Timberline Gardens) without seeing crevice gardens.  

March saw the building of what I am trying to name "Mt. Shinn."  
Both Jan's and the above Carol & Randy Shinn's rock gardens will be in the RMC-NARGS rock garden tour this year.  you'll just have to go yourself to see the rest of their glorious gardens, the older and established and more colourful bits.

Carol has done some exquisitely tight planting already in the crevices.  

I finally got to visit Ft. Collins' Gardens at Sping Creek and their hidden-jewel of a rock garden.  The designer of this garden, too, will have her home garden on tour with RMC-NARGS.  Just a black-and-white photo I saw of it was irrepressably beautiful.  I was impressed with their blooming Helichrysum mats and some large specimens of Petunia patagonica. Those are some world-class Kew-botanic-level species.  At least, I don't do very well with them...

 A small crevice garden is underway at Timberline in Arvada outside their schoolhouse, where they hold classes, which have been so popular this year that the classes have been filling up to capacity.  Maybe a rough winter left us all completely mad to scratch that green itch?

Lastly:  Sand.

In more techincal notes, the "X" section at the end of the paper, if you will: the most recent crevice gardens have been using sand as their main media component.  This is a swing back to the traditional Czech approach.  Generally, these crevice gardens have been built on top of a clay-based Colorado soil, which, underneath this rock-paved mound of sand,  must remain significatly moist and cool.  Think of the garden as a very convoluted multi-layer mulch/topdressing if you will.  The surface absorbs the water incredibly rapidly, but the the deeper layer may never even dry out. This leaves the plants with options as to where they want their roots…

Sand has meant several things.
1. It is easy to work with during construction.
2. It absolutely must be top-dressed and hidden with gravel to prevent it from washing away during rain or irrigating.
3. It settles quite significantly. My hero, Zdeněk Zvolánek, writes about carefully packing, tamping, and teasing the sand under and in-between the stones during construction.  I've found that impossible- perhaps from my youthful lack of attention span or my frenetic buidling process- to execute to the point that the sand doesn't settle afterwords. (Or maybe its the kind of sand?)  It seems that within a month or two the majority of settling happens, and I am guessing that after one full year it is practically done settling, but time will tell.  Those particularly novel and artsy-farsty crevices can settle immensely and require back-filling after a month or two.  I think the patience is worth it to wait, then refill that crevice with sand and gravel, topdress with gravel, and jam a plant on it for what must be seen as a posh high-rise dwelling for beloved plants.

On recommendation of our friend Stephanie Ferguson in Calgary, occasionally I've mixed the sand with equal parts sharp (as opposed to round/ peagravel)  gravel.  It may stabilize the sand in precarious positions.

Sand-beds are not unheard of in rock garden circles around the world.  Many plants love ot grow in it, lacking traditional organic sources of nutrition, but supplying subtle mineral nutrition. This rock garden is essentially a sandbed whose gravel topdressing is mega-sized into 800-pound stones.

Are you wondering how well it works?
So am I.
Stay tuned.

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