One of the most mind-blowing moments as a graduate student in the horticulture department was the day my class started learning about photosynthesis. At the time, I was doing a research project with elementary school students, who coincidentally, were also learning about photosynthesis in their class. Granted, my class was talking photosynthesis down to the level of the mechanisms of the light harvesting antenna complexes of photosystem II (my brain hurts just thinking about it) and the elementary students were learning plants need sunlight to make their own food, but our focus was the same topic. What struck me so intensely about that juxtaposition was how learning builds; you can keep deepening your understanding of science, or an applied science like gardening, throughout your life and there will always be more to learn. How cool is that?
One area of gardening that I find that particularly true of is plant propagation, or growing new plants from seeds, or cuttings, or even plant tissue. There numerous methods, and a lot of nuance in getting it right. Almost every adult I know planted a bean seed in a cup and placed it on a classroom windowsill to grow at least once in their school days. Most vegetable gardeners direct seed something in the garden each year, corn or beans or sunflowers or squash. But one way to kick that skill up a notch is to start seeds indoors and grow your own translplants. For many vegetables and flowers, that should be started 4-6 weeks before planting outdoors. In other words, now. And although the basics are the same, seed and soil and water and light, below are a few subtleties for this higher skill level of seed starting.
Gardeners who have made it through at least one garden season can probably tell you about the importance of temperature. There are warm season crops, cool season crops, and putting tender warm season crops out too soon could mean they will be killed by frost. Temperature is important for plant growth, but it is also relevant for seed germination. All seeds have a minimum temperature at which they germinate, a maximum temperature, and an optimum temperature and range. Soil temperature is important! If starting seeds indoors, invest in a germination mat, essentially a heating pad for seeds, so that you can program it to heat the soil to just the right temperature for whatever you are planting. Tomatoes and peppers are some of the most popular vegetables grown for transplants, because they both need relatively high temperatures to germinate, and need a very long season of growth. It just does not make sense to direct seed them in the garden. Planting indoors with a germination mat ensures that plants come up quickly and uniformly. A quick google search of “plant germination temps Extension” will bring up several good lists of germination temperatures for common vegetables.
Another element that you should include in your home germination set-up is a fan. Once the humidity dome comes off, a fan can keep air circulating, which can prevent fungal diseases from affecting your plants, but it also has a second function of strengthening plant stems. The gentle breeze mimics outdoor conditions and will toughen up plants so they can handle life in the outdoors.
How close the light fixture is to the seedlings is another factor that can make the difference between sturdy compact plants and wimpy leggy ones. The ideal distance is 2”-4” from the plants. Notice, putting them in the windowsill was not given as an option. Unlike houseplants, which are houseplants because they come from environments where they receive filtered light so the indoors feels like home to them, vegetables and most annual flowers need high levels of light. The light coming from windows is not adequate for growing strong transplants. Instead, use fluorescent bulbs. I’ve seen 40 watt recommended, I’ve seen some publications recommend a cool and warm tone (which is what I use at home), I’ve seen recommendations that say it doesn’t matter what light spectrum they are in. What the recommendations do concur on is there is no need to buy expensive grow lights. Regular fluorescent bulbs and a shop-light fixture work great. As long as you keep it close, your transplants will thrive.
Cleanliness may seem odd when talking about an activity based in soil, but in this case we are worried about fungal and bacterial pathogens that could kill our transplants before they even make it into the garden. If reusing containers from a previous year (which you should, you know, because reduce and reuse are much more important than the recycle bit), sanitize with one part bleach to nine parts water to kill any lingering pathogens. Likewise, use a sterilized potting media. Any potting soil or germination that comes in a bag is already sterilized, so that should be easy enough to do.
This is just a bit of attention to some of the details that can make the difference between success and failure starting seeds indoors. I hope these tips add a new depth to an old skill. For more detailed information on seed starting, check out “Starting Plants from Seed for the Home Gardener” at extension.uga.edu/publications.
