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--- garden:infrastructure:lowtents:temps [2020/06/28 20:11] – created davidbac
+++ garden:infrastructure:lowtents:temps [2020/06/28 21:12] (current) – davidbac
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+===== Temperatures =====
+==== Extended growing ====
+I use the low tents to extend the growing season for suitable plants-those that have some cold tolerance but which might be killed or stunted by a hard frost. In 2015 I grew mostly lettuce, chard and bunch onions in the tents. Lettuce transplanted on April 3 did remarkably well. We harvested for the Food Pantry throughout June.
+I put plastic on the tents in late March and keep it on until temperatures warm enough and the threat of frost is gone, through May. I put the plastic back on in late September and leave it on until the plants are done.
+==== What's this for? ====
+{{ :garden:comment:winter:img_2116.jpg?300|}}I don't live where some of my low tents (and hoop house) are. So I need to anticipate conditions and do needed actions in a short visit.
+I collected the following data to answer some important questions about growing in the low tents:
+  * When do I need to open the tent to the outside environment to avoid baking the plants (given a forecast for clear skies and an expected temperature)?
+  * Given a forecast low temperature, what actions do I need to take to avoid frost-killing the plants?
+So the exercise described here wasn't an abstract science experiment, but an attempt to find successful growing parameters in the low tents.
+I collected temperature (as well as humidity and solar radiation) data outside with a nearby weather station and inside by a Tempo Environmental Monitor inside the tent. I choose readings every 30 minutes for the average temperature during that period.
+I collected similar data for the hoop house, but I haven't summarized it in the same way, mainly because during the part of the season I'm growing in the hoop house (May through August) I have less need to guard against freezing, and I don't have much control over high temperatures other than opening doors and rolling up side panels.
+==== Soil temperatures ====
+In November 2015 soil temperature outside the tent was 54 degrees about the same as in late September.
+Inside a tent without row cover the soil temperatures was 57 degrees. Soil temperature under the row cover was slightly warmer (after one week) at 58 degrees.
+==== Typical differences ====
+The low tent traps the sun's rays during the day and the temperature inside increases, up to more than 15 degrees in the fall season. On a clear day I would open the tent in early afternoon and then close it around 3:00 to avoid a temperature greater than 90.
+The tent's plastic is not insulation so at night the inside temperature is generally only 1 to 2 degrees warmer than outside, except under additional row cover laid over the growing plants.
+This graph compares the outside temperature with the temperature inside the tent. Generally the difference is greatest when the sun is shining.
+{{ :garden:infrastructure:hoop:low_tent-temps42days.jpg?300 |Temperatures over a 28-day period from September through the end of October}}
+==== Row cover ====
+{{ :garden:comment:winter:img_2142.jpg?240|}}Over this period a row cover was used in addition to the low tent. This cover close to the ground added from 3 to 7 degrees to the temperature around the plants but only during the night. The cover appeared to retain more of the ground heat than the low tent by itself.
+The row cover mitigated the effect of sunlight during the day slightly reducing the warmth around the plants. Notice on the morning of 11/5 the temperature under the cover was 7 degrees warmer than the outside temperature, which was 33 degrees.
+==== Under cover ====
+This graph shows typical temperatures of November weather from sporadic sunshine with rainy, overcast days.
+{{ :garden:infrastructure:hoop:low_tent_temps.jpg?600 |Temperatures over an 8-day period in November}}
+==== Average difference ====
+During the Fall of 2015 the average outside temperature was 53.9, the average inside temperature was 57.2. That is for every half hour over that time.
+==== With little sun ====
+I had two low tents in the garden that receive all the sunlight that there is - they are not shaded.
+At home I had two raised beds that received sunlight for only about 3 to 3 1/2 hours, when the sun shined.
+Growth of plants at home was markedly slower than at the garden. I had cabbage in the tent at home and cabbage in the open at the garden. At home the cabbage was spindly and not forming heads after a month, while at the garden they were a bit stockier and just starting to form heads. It is clear, however, that growth with limited sunshine is greatly retarded. (No surprise, but I though maybe the cabbage in the low tent might keep up with those at the garden in the open.