Soils and flower color
penstemon (Thu, 14 May 2015 13:43:10 PDT)

seasonal nature of moisture is what makes these bulbs adapted to heavy
soils. Some of them grow very deep where there may be just enough
residual moisture and coolness to keep them from desiccating.
Water is withdrawn from the soil profile at a faster rate in clay soil than in sand (by evaporation), so I imagine the bulbs are pretty dry in summer. I wonder if it’s the relative absence of air in clay that keeps the bulbs from desiccating, rather than residual moisture.
So, for example, I can provide the “dry summer rest” needed for some bulbs simply by growing them in heavy soil, because it never rains enough in the summer here for water to penetrate very deeply.
If I grew the same bulbs in sand, they would rot.
Bob Nold
Denver, Colorado, USA
_______________________________________________
pbs mailing list
pbs@lists.ibiblio.org
http://pacificbulbsociety.org/list.php
http://pacificbulbsociety.org/pbswiki/