Jane McGary
Tue, 06 Jan 2009 14:01:49 PST
Rodger wrote,

>The lava rock that's widely sold as a garden top dressing is nothing 
>like real
>pumice. Pumice is porous, solidified rock foam, and quite water retentive,
>whereas the lava rock isn't water retentive to any great degree.
>This charming fact means that you can plan next summer's vacation 
>now: plan on
>visiting Crater Lake in southern Oregon. The access road along Annie Creek to
>the Rim Drive climbs to the caldera rim over enormous deposits of pumice, and
>along US Highway 97 which runs up the east flank of the Cascades, NE 
>of Crater
>Lake you go for miles through drift, banks, and hills of pumice thrown out by
>Mt. Mazama when she lost her temper some 6000-7000 years ago.

True: the mulch is what we call "scoria" and it's better as a top 
dressing than a soil component. However, you don't have to get your 
pumice from nature (if you're right near Crater Lake, it's a national 
park and it's illegal to take rock, anyway); you can just stop at 
Oregon Decorative Rock near I-5 in Portland and buy it in 60-pound 
sacks, nicely crushed.

Jane McGary

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