Question. Why so much sand in the bag mixture?  Not many plants grow in that much sand.  What would happen if we changed the ratio between sand and compost so we could sustain plants native to our area?  Is it a structural reason?

Answer. Yes sand is structural-based on its angle of repose and load carrying capacity.  We run 80/20 down to 70/30.  Many Natives will grow in these conditions, but we want to choose plants that will root into the parent material on-site – that’s where the real nutrients and water holding capacity is. Many natives will grow their roots up to 20’. Also compost will decompose and shrink with time therefore causing serious settling issues over time.  This sandy, engineered mix also allows for good percolation resisting hydraulic pressure from behind the wall.

Question: Does planting need to be done right away after the bags are placed or can it wait?  We need to be done with all construction by fall, but our vegetation unit doesn’t typically plant until winter for watering reasons. 

Answer. No it does not need to be done right away.  Agrecol recommends placing net free excelsior blanket over the wall and pinned in place.  This blanket will protect the wall from UV sunlight until the plants can be installed and shade the wall permanently.

Question: What type of root system are you looking for?  Our vegetation people would want to plant trees and shrubs (buckeye, box elder, coast live oak, elderberry, rose, snowberry, etc.)  for a deep root system.  Does that work with the bags or would that ruin the integrity of the system?

Answer: Trees work very well.  Agrecol recommends a mixture of both, grasses for the under story until the trees take hold and crowd them out.  Many native grasses have root systems 8-15 feet deep.   All of these root systems bound together will make the structure grow stronger with time!