Brock wrote:
Hi,

As it says in the subject, I'm new to gardening, and want to know
exactly what 'frost' is.

I would assume it's zero degrees, hence ice forming overnight. However
I read articles mentioning it (don't plant until the last of the
frosts, etc) talking about the Sydney area, but as far as I know we
don't really get any frosts.

Well, I guess some parts of Sydney do, but it's pretty rare where I
am, which is Ryde.

Anyway, what is 'frost'?

Thanks

Brock

Frost is condensation of water from the atmosphere that freezes to ice. The
ground temperature may be well below zero and so would objects that frost
forms on. This usually happens under a clear sky at night when the ground
loses heat by radiation. This almost never happens in the seaside suburbs
of Sydney but is reasonably common inland (eg St Marys, Penrith) during
winter. My guess is that you would get frost at Ryde but rarely. There are
local environment effects that mean some places (on a hill) may never get
frost but only a km away (in a hollow) gets frost. Rather than have people
around the world speculating why not ask some neighbours who have been in
the area for a few years.

also see:

http://en.wikipedia.org/wiki/Frost

David