Minimum temperature for plant growth is generally between 0 to 10 °C, depending on the plant. Some examples of minimum threshold temperatures for growth of some plants and insects (from here) include:
- 2.2 Spinach
- 4.4 Lettuce
- 5.0 General plant growth
- 6.0 Cabbage maggot
- 7.0 Potatoes
- 7.0 Variegated cutworm
- 10.0 Corn and beans
- 10.0 Grasshoppers, corn borers
- 15.0 General insect development
The minimum threshold temperature is used as the base temperature to calculate Growing-Degree Days. The Middle Earth Garden has about 1200 to 1350 total degree days above 5°C based on data recorded from 1971 to 2000 (see map below).
If anyone has more information on Growing-Degree Days (GDD) or related topics please feel free to share. I'm trying to find a chart of GDD for different vegetables but as yet unable to find anything.
The Lovage (above) came up after I dug the entire garden lightly with a shovel. I didn't realize it was perennial. Now I know! It came up shifted over somewhat from its former resting place, fortunately surviving the shovel abuse. Apparently Lovage is a good companion plant to almost all plants and considered a "magic bullet" of companion planting.
The rain barrels were drained dry after a temporary heat wave last Saturday and Sunday (+20 °C), watering freshly planted seeds including bush beans and spinach. The heat wave was caused by the locally well known chinook wind or less locally but more internationally well known föhn/foehn wind to be more meteorologically correct.
Today this gardener has retreated inside while the rain barrels refresh ready for the next change of winds.