Go into any garden shed and you will find a shovel, trowel, rake, starter pots, string, and nifty little gadgets you bought on impulse waiting at the checkout stand. But often missed is a soil or garden thermometer.
I admit that I gardened for years without one until one day when I asked the question,
“Why do we start X days before/after the last frost?”
The historical data for my region may or may not apply to this particular year.
- A soil thermometer helps you determine when to plant!
For most vegetables, knowing when to plant has a lot to do with soil temperature. There are detailed charts on germination percentages based on soil temperature. The Iowa State University Department of Agronomy tracks soil temperature for farmers, indicating the significance of temperature for germination. We can control moisture and planting depth, but outside of a cold frame or greenhouse, temperature is left to Mother Nature.
So I got my thermometer. Now what?
The standard for measuring soil temperature is 2 inches (5 cm) and 4 inches underground. At that depth you are not as likely to get faulty readings (e.g. surface temperature from a sunny day). The deeper you measure, the more conservative (i.e. the later) you will be when planting.
We use three different kinds of thermometers (see photo):
- A – This analog thermometer has a long probe and is easy to measure down to 4-6 inches (10-15 cm)
- B – Seems to be the most accurate, but has a short probe and is difficult to read
- C – Digital display is easiest to read, has a long probe but no auto shutoff (risk draining battery). I also question the accuracy.
A soil thermometer is just a tool, and by no means a guarantee that your seeds or seedlings are sure to thrive. But it can give you valuable insight into when to plant that is better than conventional wisdom, outdated or conservative frost dates.
(Disclaimer: Plangarden does not endorse or sell any particular soil or garden thermometer.)
So, now I have a question. I am new to Plangarden and I was preparing a new garden bed. How can I put in a soil temperature for each of the seeds I desire? I couldn’t find a section for this. Is this a new feature that is being created?
Hi Tina,
If you meant to ask where to find optimum soil temperature conditions for seed germination, you can refer to A&M University’s Extension System Data. There are many others on the Web if you google “vegetable seed germination temperature”.
If you meant to ask where in the software you can input the temperature at the time you sowed or transplanted, we would suggest you do this on the “Daily Log” section.
If you have further questions, please don’t hesitate to contact us!
Actually, I see the benefit of this in the Daily Log, but I was wondering about a TO DO list. Something that I could see that needs to be done and then check it off. Do people do this in the Daily Log section and just change the date of an item when it is done?
Tina