Friday, February 22, 2013

(The Art of) Inorganic Mulch

Inorganic mulch seems a contradiction.

But in dry regions, even some wetter places' uplands, the ground is more gravel or aggregate than soil rich with organic plant litter; it too insulates soil at plant root zones from drying. Xeric plants are often finer textured and tend to perform and look better in aggregate, especially under 3/4" in size - inorganic mulch.

Neutral colors rule, especially when related to the site's own substrate type. But mixing gravel sizes is something I learned from peers in Tucson and the Las Cruces / El Paso area recently. Some thoughts -
Typical built landscape in desert SW towns: one gravel type and size, sparse plants (I like negative space, but...)

Using one 
gravel size isn't bad, but mixing sizes looks more natural, hiding imperfections; realities without a full-time gardener or spare time - litter and wind-blown sand are but a few. Using ample plants for one's ecoregion helps complete a space, too.
Typical natural landscape near desert SW towns: different gravel sizes, mostly the same type (even Las Vegas has had Mojave Yucca, Catclaw Acacia, White Bursage and Creosote at a density sustained by 4" average annual precip.)




An appealing mix of gravel, or aggregate, sizes upon a closer look - this surface is often termed "desert pavement

An example near Albuquerque shows desert pavement from another rock type; that past post - here
A built landscape with a mix of gravel mulch sizes: different sizes of same aggregate type in Tucson, obviously with proper maintenance priorities in skill and budget (and yes, xeric native plants like Palo Verde, Turpentine Bush and Creosote)





Closer in, with a boulder, appearing like it and the gravel are from the same geologic area
A built landscape with a mix of gravel mulch sizes: some variance of aggregate sizes of same type in El Paso (and young native and adapted xeric plants such as Desert Willow, Deergrass and Gray / Blue Sotol)

Some don't agree on my opinion the benefits of mixing gravel sizes any more than collaborating to take the stormwater from the roof and storing / using it to benefit the landscape, minimizing erosion. (i.e. 8/1/2006 - here) But I tried...
Another view of varied gravel mulch types, plus native and adapted xeric plants (add in Red Yucca and 'Rio Bravo' Cenizo) This young landscape has a different budget and maintenance priority than that Tucson project had. But again, I try...

The same, but closer-in (with local native, Blackfoot Daisy / Melampodium leucanthum)

I specified a mix of 50% - 3/4" size granite gravel, with 50% - 1/4" minus decomposed granite screenings. The kind landscape contractor ordered it mixed that way by their aggregate supplier. The west slopes of the Franklin Mountains, where this project is located, are primarily granite-derived, hence my choice.

I wasn't going to add in plants and water harvesting, but it seemed to relate; I hope that helped!

15 comments:

  1. I agree...the mix of sizes, even with the inclusion of some larger rocks/boulders lends it a more relaxed, natural feel...it sits easier in the landscape, whereas the huge expanse of one material seems far more contrived.

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    1. It's still amazing people think lawns and gravel are the same thing in how they treat each!

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  2. The proof is in the pictures showing the natural mix looks so much better. Landscapers must prefer the contrived look because the client can see what they paid for. Educating the client is part of the process.

    We instinctively mixed in larger rocks to break up the sea of 1" river rock we acquired with the house. Seeing this post shows me how we could have done even better.

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    1. I think so, and the uniformity of it is like their over-pruning of plants - accomplishment. With your place, I can see how over time, it will mix nicely...in my El Paso example, we have dust storms to do that mixing and softening work!

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  3. Seems some clients want the natural look...just not TOO natural.

    Everything is better, with different textures. Even with foliage, different textures means more interest.

    We have people here, who had loads of 2" river rock brought in and spread over the front yard. And, that's it. No plants. No boulders....nothing.
    Maybe I should do a post on that, along with photos of the yard right across the street from them, with multi-sized gravels and xeric plants. So much nicer.

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    1. I had to go back to a more uniform look w/ washed gravel of 1 size w/ one client, recently. Maintenance-driven...was picking my battle to get other things, which I think I did!

      You should post on both of those...no-maintenance vs. a more balanced low-maintenance space.

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  4. In the fourth pic down from the top, the the gravel mix adds to the lanscape. It is a good marriage between landscape and biulding, feels like the two belong with each other.
    Good lesson, thanks!

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    1. I hadn't made the connection of the building and the gravel mulch, but you're right on that. All in all, such a great dialogue in that photo that might work especially in red sandstone parts of the Intermountain region.

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  5. This could not have come at a better time David! You will see soon - I am applying all of what you said and I am so stoked! THANK YOU!

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    1. Very cool - I felt I just *had* to post on this issue ahead of mulches in general, so I can't wait to see your latest project!

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    2. Okay - close to having the granite/rock brought in and help installing it.... I have the bones down for the backyard! FINALLY! SOOOOOOOOooooo excited.

      Question - I have a parking area and an informal patio area and paths - can I utilize this mixing approach for all? As in, is this "rock mulch mix" good for only mulching in planting areas or can it be utilized effectively for patio/fire pit/paths as well?

      Thank you in advance!!!!!!!!!!!!!!!!

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    3. Wow - I'm just starting to make progress on my transplanting, borrowing, etc work! No lighting fixes yet...

      Personally, I think mixing and the textures draws too much attention to traffic areas, as opposed to where you want attention in the planting areas - so I would opt for one aggregate size visually in paths and parking. And varied sizes in the planting areas differentiates those from where one can walk more freely, until plants fill in and they do some of the work, too.

      Vehicular areas BTW best to have 3"+/- road base course, compacted in 1" layers...then 1-1-1/2" depth of DG or crushed gravel compacted in 1/2"-3/4" layers. Part of compaction = water. But you prob already know it. Just read some of that in Pam P's book, too.

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  6. Very educational, thank you! I've also seen the "2 inches of the same rock everywhere" approach to gardening, and it looks strange. I like the variation much more... I'll have to keep this in mind for my gravel garden, and some other projects.

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    1. I especially like varying rock sizes in water harvesting swales, but it's great everywhere.

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