Germination can be frustrating: you might have just invested a pretty penny in some seeds, waited a long time for them in the mail or gone to some great lengths to acquire them one way or another. Even if they’re just some random bag seeds you never expected to get, waiting for the first signs of life can be nerve-racking.
To avoid the wait and to be more successful germinating all around, there’s one thing to keep on mind that often gets overlooked: proper soil temperature. Germination rates for the seedlings of any plant are highly temperature dependent; most seedlings like warmer temperatures during the day and cold at night.
Some seeds like it hotter and some a little cooler. The tomato plant, which is often compared to cannabis in terms of cultivation, prefers a soil temperature of 85 °F for germination. Hot-blooded corn and cucumber seeds like 95 °F and have trouble popping below around 55 °F, while spinach seeds are most comfortable at 70 °F but can still germinate at 35 °F. All plants generally take longer to germinate when it’s chilly, and keeping temperatures above 75 °F should keep germination time under a week.
Another issue to consider is night temperature; colder nights at around 60 °F are healthy for seedlings and mature plants alike.
To help foster a good germination environment, try keeping a lamp over your seedlings during the day and monitor the temperature with a thermometer. Incandescent or high pressure sodium bulbs will generate heat and warm you seedlings plenty, while fluorescent and LED lights won’t provide much heat all. If the seeds are in a room that gets chilly at night, turning off the light will fulfill the plants need for a cool nocturnal environment. A simple timer and a 60 W incandescent bulb are pretty much all you need to help solve the temperature issue if you only have a handful of seeds.