A friend recently asked if it would be safe to plant out her tomato seedlings. Good question.
Please, please, do not let the current weather patterns fool you. Yes, our daytime temperatures have all been in the double digits so far this month. Pretty much okay for tomatoes, cucumbers, beans, and squash to go into the ground. However…
It is actually the nighttime temperatures we should pay attention to when we are transplanting our seedlings into the ground.
Knowing the soil temperature is also useful information when sowing seeds, as vegetables have preferred heat needs in this medium as well. Tomato plants, for one, do not perform well when overnight temperatures drop below 15.5 C for a few days. The results can be stunted growth and poor fruit set. (One or two nights is okay but more than three in succession can have an impact.)
Soil temperature: if readings are below 10 C, root development will likely be poor and growth stunted.
Do not forget about temperature needs for our pollinators. Many of them are not very industrious when daytime temperatures are below 10 deg C. So, even if some flowers develop, there may not be pollinators around to do their bit for fruit set.
One more factor to keep in mind when planting your garden: last frost date (LFD).
March 18 was the last night of frost in our garden this spring. So far. This has me worried. LFD in 2015 was on April 14. Still early for us, as LFDs have typically fallen between April 28 and May 10 in previous years. March 18 is just too freaky to think about, so I think there is a “bump” still to come.
I have not planted our tomatoes in the greenhouse yet because the overnight temperatures in our unheated structure are only averaging 6.5 C to date.
For more information on ideal temperatures for planting your vegetables, check out the chart on my website at duchessofdirt.ca
Leslie Cox co-owns Growing Concern Cottage Garden in Black Creek. Her website is at duchessofdirt.ca and her column appears every second Thursday in the Record.