When talking to folks in other parts of the country I
sometimes like to fudge a bit and emphasize the warm temperatures we are
enjoying here at the farm during the day. I guess this is because most non-desert locales experience less drastic
temperature swings than we do in a typical twenty-four hour period. So when I tell others that it’s 61degrees
Fahrenheit, I neglect to mention that the night-time low was 23 (minus 5 degrees Celsius).
Although some plants, like red mustard seem more-or-less
able to tolerate the extreme night-time lows, most plants quickly give up the
ghost without some form of protection. So every evening at dusk,
Love Apple Farm undergoes a
transformation. All our plants are
covered up and tucked-in, beneath sturdy frost blankets. These coverings are truly life
savers for the plants, and for the farm, since our winter garden must continue
to produce throughout even the coldest months. We also cover the rows inside our giant hoophouse, as the ambient interior temperature will only be about one degree warmer than the exterior during the night.
We mostly use the heaviest frost blanket available, which is rated to protect up to 10 degrees below freezing (although they seem to work just fine even lower than that). These blankets can be purchased lighter weight as well, which will allow more sunlight in. Since we use the heavy, we must uncover the rows first thing in the morning. You do not want to uncover until the temperature is above 32 degrees (0 degrees Celsius). If you do, very sensitive plants (like lettuces) can still be damaged.
We use a min-max thermometer when tracking our daily highs and lows. This is an ingenious
device which tells us what the low temp was. As the mercury drops through the night, it pushes an indicator bar along
with it. When the mercury begins to
rise the next morning, the bar remains in place – letting me know exactly how cold
it got. As you can see here, the low was 23 (see the bottom of the blue line on the left?). During the day, the high was 53 degrees (see where the bottom of the blue line on the left stopped). You can also see that the current temp when this photo was taken was 32 degrees (the top of the mercury on the right bar).
Serious gardeners will want to invest in a min-max thermometer to track their frost dates. There are some pretty space-age min-max thermometers out there right now, which not only tell you the high and low, but at what time each was achieved. If there is a dedicated gardener in your life, this would make a great gift, along with a garden journal in which to track their temps.
Understanding your own microclimate is important in that it can be very different from what the forecast predicts. Although we check three weather reports daily here at Love Apple Farm, our own temperature is frequently ten degrees lower than what is forecast.
Knowing your own first frost date is an important indicator
when it comes to planning your winter planting schedule, since you need to
achieve a certain amount of plant development before the deep cold sets in and
stunts plant growth. Keeping a journal
of daily lows and highs is a good way to build up the detailed knowledge of
your microclimate that will allow you to grow better winter veggies.
Its been cold here in Northern California but I am still harvesting kale, mustard greens and cabbage out of the garden.
I use a thermomenter like this in my greenhouse where I have Arugula and various greens planted.
Posted by: Sue Bateman | December 21, 2007 at 10:40 PM