Re: Clematis & Rocks

Cathy, IMO, the deeper the layer of gravel, the cooler and moister
the soil under it will be - a thin, one inch or less layer of gravel
doesn't do a whole lot; it's better than bare soil but not by much.  
A thicker layer of gravel acts like a large rock in keeping
underlying soil cooler - keeping it shaded from the sun. 

Pam, I use pea gravel as a topping to my sandbed because it drains
well.  Draining well doesn't mean that the soil stays dry under it,
just that water moves through it fast - which is what your herbs are
liking as all of those you mention want sharp drainage.  They don't
want water sitting around their crowns, but do need some moisture at
the roots.

As for warming - the top surface of a gravel mulch will be warm, but
the soil under it will be cooler than the air temperature.  It will
also be moister than exposed soil because the gravel (like about any
mulch) will reduce surface evaporation.  This will not hold true if
the soil under the mulch is full of tree roots as they will suck up
all available water when it's hot and dry.  

Marge Talt, zone 7 Maryland
mtalt@hort.net
Editor:  Gardening in Shade
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----------
> From: Pamela J. Evans <gardenqueen@gbronline.com>
> I don't know but I use a 2" pea gravel mulch in my herb bed because
it
> does NOT hold moisture and it gets warm, but that's what the
xeriscape
> stuff (lavender, rosemary, thyme, artemisia and ornamental sage)
loves!
> Maybe stone is different?
> 
> Wish the Bermuda didn't like it as well, but it's less invasive
there than the regular beds...
> 
> ---------- Original Message ----------------------------------
> From: cathy carpenter <cathyc@rnet.com>
> 
> >Could be true. Most examples of rock mulch I have seen were
nowhere 
> >near 2" in depth. Guess I'd need to see a controlled study of some
sort.
> >Cathy

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