Spring bulbs are beginning to bloom, and with each reminder that spring is on the way I think more about starting my vegetable garden. Every gardener knows that the question of when to plant is always a struggle. Maximizing the growing season while minimizing plant loss due to surprise cold snaps and frosts is always a balancing act. Living at high elevations can make this even more difficult, so I decided to do some research and see if I could get a better picture of what my garden and I are up against.
The first thing I needed to find was information about the temperature tolerances for vegetables. I found a great table at the Colorado State University Extension that provided acceptable germination temperatures as well as information on how temperature-hardy the young plants are. I created a floating bar chart in Grapher 12 to depict this information.
Grapher 12: Floating Bar Chart of Vegetable Germination Temperatures
This graph makes it clear that cold season vegetables can be safely planted when the soil and air temperatures are above 40°F, and warm season vegetables can be planted when the soil and air temperatures reach 60°F. With this in mind, I went searching for historic temperature data. I found normalized daily air temperatures on the National Oceanic and Atmospheric Administration (NOAA) Climate Data website and daily soil temperatures on the Natural Resources Conservation Service (NRSC) website. I then created a line plot in Grapher showing the average temperature for each day of the year and added horizontal function plots to show the cold season and warm season vegetable temperature tolerances.
Grapher 12: Line Plot of Historic Air & Soil Temperature Averages
This graph confirms the general rule of not planting warm season vegetables until after Mother’s Day (mid-May). However, I was surprised to see the average soil temperature trend so closely with the average high air temperature indicating that cold hardy vegetables can be planted as early as mid-March.
I know that there is an overwhelming amount of information available online about planning and planting a vegetable garden, but it’s always nice to see data specific to your area. Grapher 12 makes it easier than ever to create meaningful visualizations of your data!