Early Mizuna.

OSU gardening extension says Mizuna can be direct sown when soil temps are 40
degrees F:

http://extension.oregonstate.edu/gardening/node/969

There's some nice government weather stations with all sorts of information, but
not quite in Portland.  It's either in Aurora, Oregon, or Forest Grove, Oregon.

http://www.usbr.gov/pn/agrimet/agrimetmap/fogoda.html
http://www.usbr.gov/pn/agrimet/agrimetmap/araoda.html

Looking at the charts, it looks like Aurora shows around 40 degree soil temps
around early February.  Since I'm using a clothe, they should be protected from
frost dips into the 30's.  So start Mizuna around the time I start Spinach, and
see what happens.

Signed-off-by: Sarah Sharp <sarah@thesharps.us>