Rooftop gardens are the rage in Central Texas right now.  Landscape architect and design firms are all over the news for their efforts to turn high rising frying pans into cool pools of grasses that blow in the wind and protect buildings from searing Texas heat.

Lofty gardens present new challenges for landscapers:  they’re shallow; they’re hot; they’re heavy.  Even a small bed can weigh tons, which creates novel stress on structural components of roofs, which are not traditionally designed to support huge weight loads. 

Over the last 4-5 years, soils in the rooftop beds of City Hall have supported the small native trees, grasses, succulents, and perennials beautifully. But, as the organic components of these soils have broken down, the soils have subsided over a foot in places. This is a relatively large proportion of the shallow beds, so we are attempting to replace the void.

We can’t just dump random stuff in there.  To avoid the embarrassment of a bed full of sotols crashing through the ceiling of the Council Meeting Room and possibly puting out an eye down there, we needed to re-create the exact mix that matches the original.  Nothing too heavy, nothing with too much compost, nothing that drains too slow; we needed to find the baby bear version.

The original provider of the City Hall rooftop soil mix, a giant nationwide supplier of landscaping stuff, no longer has an Austin branch.   When Rich called the Dallas branch to get some help, they tried to tell him their blend was proprietary.   A mix of expanded shale, sand, and compost isn’t exactly a product of millions of dollars worth of research and development, but I guess you can’t blame the guy for trying.

With no help from the big bad corporation, and no local provider of that super secret blend, we decided to make some ourselves.  

The nearest source of expanded shale comes from a mine..er, quarry..uh, pit… south of Dallas.  As far as we know, Natural Gardener is the only local soil yard who purchases this expanded shale in bulk.  So we picked a couple yards there, took it to George at GeoGrowers, who added his microbial and nutrient rich magic dust and sand to create….well….our own “proprietary” blend of rooftop garden soil!  We call it BioGardener and George’s Famous Rooftop Soil Blend for Central Texas Sky Gardens.

Stay tuned for results as we apply the BrAGFiRStBeForeCloTSGrow product at City Hall over the next few weeks and months.  We’re hoping we get the blend right, but with George involved, are confident we will.   If we can help him create a commercially available rooftop garden mix, tried and tested, we could potentially help reduce the average ”soil miles” for all those new rooftop gardens in Central Texas, and just might help make local green roofs even greener.

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