Steep Dry Hillside Transformation With Vetiver Grass and Natural Stone

This South-facing hillside has a grade ranging from 55-65%. The soil is very friable, dry and has little perennial vegetative cover. The slope was formed when the lot was graded for the house site and has been steadily slipping, its edge creeping closer to the house with each passing year. This post details how we took it from dry, inaccessible and eroding to a vegetated, accessible and beautifully stabilized part of the property.

View from the bottom looking North – first batch of rocks have arrived for constructing the pathway that will create safe access to the bottom of the property.

Flags show the approximate course of what will be a meandering rock pathway leading up to the house.
Looking West where the green flags mark the proposed pathway.

The pathway is being installed across the slope so as not to be too steep. If it didn’t cut across the slope we would have had to use zipper stairs or some similar format to cover all of the rise without using too much run. This style, while useful, is not the best for a relaxing stroll down through the garden.

Looking Southeast from the top of the slope down the proposed pathway route.

The process used to build the rock pathway is largely intuitive and based on observation of the site and the known needs of the residents. One primary need is the ability to access the gate at the bottom of the slope to easily take the dog out for walks in the adjoining open space. Simultaneously the need for an option to go to the other corner of the yard is also important. That combined with the steepness of the slope made the arched stone buttress a logical starting point. This created a split in the path, improved access to each side of the lower yard, made this lower section less steep, and also created a sun trap backed by lots of thermal mass – hello heat loving plant guild!

End of Day 1 – the lower buttress has been installed and 11 elevation changes are in.
View of buttress and steps from the East side looking West.
Halfway up the buttress and looking at the first three steps that go directly upslope.
View from mid-slope looking Southwest – lower gate with open space beyond visible in the upper left corner.

The pathway is built from the bottom up so that each step is keyed into the one below it, either with direct contact or sitting on a compacted dirt backfill uphill of the previous stone. This is critical for stability given the fragile soil and steep grade of the slope.

We began planting vetiver rows on contour while the pathway was still in construction. Each row of vetiver was planted into a narrow (3″ wide”) trench underlaid with a 12″ wide strip of burlap for temporary, biodegradable root protection from potential root-eating vermin and filled with composted steer manure. Each row of vetiver is fed by a 1/4″ irrigation line with emitters every 6″ to ensure successful establishment.

Each rows of vetiver is set 18 vertical inches below the previous one.
Completed pathway from midslope looking towards the top. All rocks are keyed into the one below and the upslope and downslope edges of the pathway are also planted with vetiver slips every 4-6″ to create a ‘biological pylon’ effect to secure the soil around the rocks.
The plan shifted as the project neared completion and the pathway went straight upslope the last 5 steps. Gaps between the rocks were filled with composted steer manure and planted with an experimental drought tolerant grass groundcover Zoysia tenuifolia (aka “Korean Grass”).

 

 

View from top of path looking downslope. Brown line in the foreground is the 1/4″ irrigation line feeding the top vetiver row.

Completed pathway and view of all seven contour vetiver rows. Phase 1 complete!

Watch a 9 minute video journal detailing the installation process of the pathway and the vetiver grass.

Here’s a quick update video of the vetiver’s establishment – filmed 6 weeks after the last vetiver went in. The whole hill side is 4 foot tall green grass!

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