Less Noise, More Green: Germinating seeds indoors: some like it hot, some like it cold

Thursday, April 10, 2014

Germinating seeds indoors: some like it hot, some like it cold

starting seeds indoors, heat mats, stratification, grow lights

I love my grow lights. They have made such a difference to the success of my garden. Living in a region with a short growing season, being able to start seeds indoors dramatically extends my growing time and in some cases has allowed me to get two plantings in before the first frost. Using heat mats and cold treatments are great tools to help some seeds germinate.

starting seeds indoors, grow lights, heat mats, stratification

Most seeds like room temperature to germinate. Some like the light, some the dark, all need moist soil.

Some seeds, however, need heat to germinate, with the soil temperature at 80 to 90 degrees F. To achieve this you need to use a heat mat which raises the soil temperature by at least ten degrees above room temperature.

You can see the difference in temperature the heat mat makes by the condensation on the tray lid.

This year I'm growing eggplant, bell peppers, jalapeno peppers, tomatillos, ground cherries and several kinds of tomatoes, all of which need heat to germinate and grow. I keep the lid on the tray to create a green house effect until 60% of the seeds have germinated, then I take the cover off. Once all the seeds have germinated, as long as the room temperature is 70 degrees or higher, the seedlings no longer need to be on the heat mat.

Aster seedlings, stratification, starting seeds indoors
Aster seedlings

Other seeds need cold to germinate. This is called stratification, the process by which low temperatures in a moist environment awakens the seed and encourages germination. This year, I'm growing two plants that need stratification- Asters and Violas.

Both of these flowers need stratification to germinate.

The fridge is the obvious place for this process, of course. These clean plastic takeout containers with lids are perfect for the job. Sow the seeds as directed in the tray, moisten well and leave in the fridge until the seeds sprout. The Asters took about three weeks and the Violas will take five days. With the Asters, I sprayed the soil to keep it moist about once a week. Now that the seeds have sprouted, the Asters are doing well under the grow lights.

seed potatoes, stratification

Also in my fridge right now are two dishes of seed potatoes. These will be planted in potato bags in a week or so, but until then they will stay in the cold as their eyes develop.

Reading the information on the seed packets is so important. It is easy to miss a step like optimum seed germination conditions if you don't look for it. Who would guess Aster seeds need three weeks in the fridge by just looking at the front of the packet? When your growing season is so short, waiting on seeds that wont germinate in room temperature conditions can mean the difference between having a crop or going with out!

My only lavender seedling, so far.

Speaking of which, on my second attempt at germinating Lavender, I have a seedling! First time, I tried germinating with heat. Nothing. This time I tried a mix of heat and then no heat and it seems to be working. Lavender is known for being temperamental. I'm glad I didn't give up on the plant and tried again!

See you in the garden,


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