Best soil for a raised bed?

Sun, 20 Jul 2014 10:20:12 PDT

At this point, I feel like I almost have to try a sand bed, just to see
what'll happen. Will the roots grow throughout the sand, dive down into the
clay, or descend to the top of the clay and then spread horizontally?

Only if they have a death wish. (A lot of plants seem to.) Plants adapted to
growing in coarse, highly-oxygenated soils would have no reason to try
sending roots into a heavier soil. They would suffocate.
I made the raised beds here in order to grow a variety of plants naturally
adapted to coarser soils; the clay here (which is subsoil trucked in from
some other place, like hell) has the consistency of frozen ice cream when
wet. Plants growing in the clay do have an opportunity to send their roots
down to the native soil, which is decomposed sandstone, before they're
asphyxiated by the clay above the native soil. Doesn't always work.

(Unlike most gardeners, I have little interest in growing plants not suited 
to my rainfall. A large number of summer-rainfall South Africans are 
perfectly hardy here; nerines, gladiolus, crocosmias, eucomis, etc., but 
they require so much irrigation in summer I would have to hire an assistant 
to water them every day. Or invest in an irrigation system.)

Matching the plant to the soil is always a good idea. This is true with
rainfall patterns as well. If you were growing a lot of Cape bulbs in a soil
very similar to that of the native habitat, you probably wouldn't have to do
anything, except maybe gloat.
I suspect that information on habitat soils is readily available.  (If you
come across the word "drainage" in reference to a habitat soil, what is
really meant is "highly oxygenated".)

Bob Nold
Denver, Colorado, USA

16 percent humidity ....a little high for me 

More information about the pbs mailing list