06/17/2026
This is such good information! Our cool weather in Calgary is not helping the tomato situation here either. Tania
This is why I HIGHLY recommend not planting your hot weather plants like tomatoes, peppers and eggplant among others until roughly two weeks after last frost which is June 8th this year. If you have a heated greenhouse that is a different story.
When temperatures drop below 10°C, the plant's photosynthesis slows significantly, resulting in much smaller plants and delayed harvests.
Exposure to chilling temperatures (below 10°C to 13°C) directly before or during flowering negatively impacts pollen viability. This causes poor pollination, a low rate of successful fruit set, and increases the likelihood of misshapen (catfaced) fruits.
Below 12°C to 14°C, the plant’s roots struggle to uptake essential nutrients like phosphorus, which can cause a purple discoloration in seedlings and leaves. Cold-induced stress also hinders the plant's ability to utilize calcium, leading to disorders like blossom end rot in early developing fruits.
Personally I will be taking advantage of the nice daytime temps to harden them off really well until planting time.