Dasylirion leiophyllum in new rock berm

[westfork]

Making use of crevices in the rock berm that is slowly taking shape in front of the house. Here is a dasylirion leiophyllum nestled between a couple boulders on the face of the berm. It is the one grown from seeds collected by David Salman that PDN calls good to zone 5A - We will see. The small red rock in front will be removed once roots are established. Glacier erratics are considered junk but these boulders can be put to good use creating raised garden beds.




One was a bit too large for me to shove into place with my loader. Thankfully payloaders and telehandlers are standard farm equipment nowadays and flagging down a passing neighbor kid for a few minutes of help can place that stubborn rock.

[GLF]

I really wish i had something like that to move my rocks for me! Then i could get bigger and better rocks like yours.

What mix have you planted the Dasy in and how old is it? I have some D. leiophyllum seed to plant in spring but I'm guessing it will be many, many, many years until they're at that stage.

[westfork]

At least your rocks match. We have no bedrock here and these glacier erratics came down from Minnesota and Canada and are a mix of many different types, mostly granites and the nearby Sioux Quartzite.
For the top of the berm, which is 55 feet long and about 12 feet wide, my soil mix is 2/3 river rock (1/4" - 1 1/2") and 1/3 topsoil, with a good slope to the south and southwest. In areas near the edge of the berm I have some mostly rock aggregate that drains out the side for very xeric species.
The soil mix for that dasylirion I planted yesterday was about 60% pumice, 10% pea gravel and other fine rock, and the rest a little topsoil, potting soil, and coarse coir for a bit of nutrients and water retention. The organics will wash away over time. The slot filled with this mix is 16" long by up to 8" wide and a foot deep, but it is underlain by 1" sharp rock at least 18" deep that I set down to support the boulders and minimize frost heave, as well as supplying a deep drainage channel away from the berm.
Here is what I move the boulders up to 3000 pounds with. The bale and cat keep the rear wheels on the ground. In the foreground is the top of the packed rock under the boulders, this side is now buried under the berm. The channel dug out for this rock provided the topsoil for the berm

berm construction

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[GLF]

Looks like i need a cat to help supervise all my rock moving. How deep is the river rock/topsoil mix within your berm? I'm doing a similar size bed myself and trying to get an idea how deep i need my amended layer should be.

[westfork]

But cats can be very demanding and terrible supervisors. I am filling the whole berm with that mix down to the native grade beneath it - So from two to almost three feet deep. Many plants have roots much more shallow than that but I figured the increased drainage couldn't hurt. The native loess soil beneath it drains well also.

I am experimenting with pockets of excessive drainage for certain plants. Of course, if you just dig a planting hole and fill with a coarse aggregate you may end up with a bathtub that drowns the plant. But I am digging the holes adjacent to where boulders come together and allows water to escape laterally through the gap.
Here is the start of such a hole:


And here filled most of the way with river rock, worked into the bottom and side enough to incorporate a little soil:


Higher up threw in some 3/8" pumice for the finer surface roots:


And then planted in a thin layer with more nutrients and covered with the soil/rock mix to deflect some moisture. Ignore the pile of soil behind it, this will be spread to the south as I complete that section of the berm. The surface will slope away from the plant.
The free draining area of the planting hole can drain through the gap between boulders and the roots can reach out to adjacent areas if searching for more moisture or nutrients:

[GLF]

Sounds like i should stick with our cocker spaniel to approve rock placements in the new bed. I like the look of all that drainage, especially around each plant. Will definitely need more gravel than i was thinking. We've had around 50" each year for the last few years but luckily don't get below -1oC/30oF. Good luck with berm and looking forward to seeing it progress

[westfork]

Another thing I am doing for drainage is scattering dwarf conifers around the bed to suck up surplus moisture. Using Jerry Morris selections from the northern Rockies as they approximate our climate. Just popped in some dwarf Limber Pines tonight and added

dwarf conifers in berm

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a dwarf Ponderosa a couple weeks ago. The challenge will be keeping them wet enough to establish roots in the fast draining mixture but without too much moisture which they hate. A normal Ponderosa Pine (eastern race) in background.

[westfork]

Sounds like i should stick with our cocker spaniel to approve rock placements in the new bed.

Yes, too many cat supervisors are hard to please:

Cats supervising rock placement

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Getting some of the smaller rocks placed on the back side of the berm. A couple every evening when we have the time. The biggest challenge is picking the ones that fit together the best.

Placing small rocks on back of berm

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[westfork]

Added a couple more cubic yards of the 2/3 river rock / 1/3 topsoil mix to get the ridge slope right on the south end of the berm. After I drop in a rock or two on top the south end can be planted.

south end of front lane berm

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It is a break between the lane on the east and lawn (beaten down to bare dirt at the moment) on the west.

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That 2.5 ton moose of a rock makes a good prow for the south tip. It should discourage grain semis from getting too close.

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Next phase is to place smaller rocks along the low east side of the middle of the berm - dotted orange line.

Start middle east side of front lane berm

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