While we’ve started some garden seeds indoors for three years now, in an effort to increase efficiency and seedling yield, this year I went all in on seed germination research. I wanted to create the best environment for these little embryonic plants that hibernate within their seed coverings until the right conditions present themselves for development.
Ideal seed germination depends on the species you’re planting. For example, when it comes to some flowers such as the Tall Russell Lupine I’m trying this year, a period of cold akin to what the seed would experience in its natural environment is essential to prepare it for germination. (I’ll share my Lupine seed starting experiment in an upcoming post, so check back if you’re interested.) Seeds like the Globe Amaranth I started last weekend benefit from a 24-hour soak in tepid water to soften up their tough and protective seed coating.
But for most of the food-bearing plants I’m growing for our kitchen garden, as long as I create a growing environment that contains an optimum temperature for my seeds, evenly moist soil, and consistent and adequate light for 16 hours a day, I can count on adequate germination rates for the seeds I’ve sown.
Optimum Temperature for Germination
Here again, the plant species you’re cultivating plays a role in the ideal seed germination temperature for the plant. To get a sense of temperature variation for your garden seeds, this site provides a straightforward chart detailing optimum germination temperature for vegetable seeds. Not surprisingly you’ll see that some seeds need warmer temperatures than others to get growing.
If you live in a colder growing climate like I do, you quickly separate the hot-weather vegetable seeds from the cool-weather seeds. Not only is it essential to start hot-weather seeds like hot peppers, eggplant, and tomatoes indoors under consistent light, but if you’re hoping for good germination, you will want to throw down money for germination heat mats so that you can create the warm environment (77 degrees F to 85 degrees F) these seeds need to get to work.
I will say that I used heat mats under all of the seeds I’ve started in the last few weeks, and the germination rate has been almost 100%, even for cool-weather seeds such as cabbage and cauliflower.
Good Lighting = Happy Plants
Our house may be the warmest place on our property for much of fall, winter, and spring, but it’s also small, so the only reasonable space the utilitarian task of seed starting is the basement, which while not dank, is dark and chilly. Fortunately, with a small upfront investment in grow lights, we’ve been able to create a great seed-starting operation in a nook of our basement.
If you have plenty of space and amazing south-facing windows, you could try to start seeds with just the light streaming through your windows. After listening to gardening expert Margaret Roach’s seed-starting series on her podcast Away to Garden, though, I’m convinced that starting seeds under grow lights boosts germination rates and gets them off to the healthiest start indoors since the lighting is consistent and doesn’t have obstacles like trees, house eaves, or other people’s houses impeding access to sunlight.
For our basement grow system, we drape two inexpensive reflective “space blankets” over a two-tiered shelf and a DIY wood-framed grow system to prevent light from escaping and to direct that light back to the seeds for maximum energy efficiency.
Adequate Moisture
Last but not least, the non-soil seed-starting medium you use for germination must maintain adequate moisture levels to coax the seeds to soften and open for germination. While you don’t want a soupy seed-starting situation, you do want to keep the top of the mixture moistened (an inexpensive spray bottle filled with water is key for misting), and to encourage strong root development, you want to water from the bottom up.
Lots of options are on the market for seed-starting containers, but I’ve had the most success with seed cell flats that not only come with a humidity dome but also include a self-watering capillary mat that sits directly under the seed cells and draws water up from the flat through the capillary mat, offering consistent low-level watering to the bottom of the seed cells. The roots tendril toward water and encourage stability while the sprouts stretch up toward the light.
Interested in learning more about seed starting for your garden this year? Check out my seed starting post from last year here. Colorado 5b gardeners still have time to start tomatoes, peppers, and eggplants indoors if you hop to it this week, and now is the ideal time to start seeds indoors for most flowers and brassicas if you’d like to get them out in the garden by mid-May. Good luck!