The soil mix should provide support for the plants, hold water and nutrients and allow for easy root penetration. Don’t use a dense mix. Luckily, there are a number of options available. You can use commercial mixes that can be purchased here in town, or you can make your own soil mix. Some possible homemade mixes include equal portions of bagged topsoil or potting soil, peat and a sharp sand. You can change out the sharp sand with perlite or make a mix with two-thirds topsoil and one-third peat. I mention bagged topsoil or potting soil because using soil from your garden could introduce insects or diseases into the soil mix and tender seedlings might be more susceptible to them. You can sterilize garden soil by heating it in the oven, but you won’t like the smell it generates in the house.
Choosing a container
The package of seed will usually include information about proper seeding depth, but a general rule of thumb is two to three times as deep as the thickness of the seed. Containers for growing plant starts can vary widely but many people use a long tray or a flat, which also can be found locally. Make rows 2 to 3 inches apart, planting the seeds in each row. However, this method requires you to carefully prick out, yes that is what it’s called, the seedlings and plant them into bigger containers such as a 36 or 72 cell-count flat. Or you could seed directly into the cells on a tray, or use a soil filled fibrous pot or even one of those discs, which are compressed soil that you soak in water so they swell up, and plant directly into that.
It’s critical for good germination that the soil is kept moist but not waterlogged. Allowing the soil to dry out much can slow down the germination of the seeds or even stop them from germinating. So keep watch on your soil, checking daily to get a feel for how your particular potting mix is holding water. Once the seeds germinate and start growing you can cut back the water. You should still keep it mostly moist but it can dry a little more than during the initial germination process. Once roots develop, it’s critical to watch watering to prevent any root rot or damping off disease.
Light is very critical for getting a compact bushy plant, which is what you want. You can use sunlight but if raising seedlings in a house it’s unlikely that will be enough to get the bushiest growth. Incandescent lights are one choice, if you can find them, but they are hot and have to be placed carefully around the plant. A better option is to use fluorescent lights, which are energy efficient, easy to install and last a long time. Cool-white bulbs provide light in the blue end of the spectrum, which encourages compact bushy growth. Warm-white bulbs provide light in the orange to red spectrum, which is good for flowering and some foliage growth. But if it is too strong, this type of light can result in leggy or spindly growth.
Position the lights carefully since you don’t want to be heating up the plants. Check this by placing your hand above the plant to see how warm it is. Generally with fluorescents you might be looking at placing them 4 to 6 inches away from the plant, while incandescent light might be 12 inches or more away. You can buy special grow lights, but this is rarely necessary if you’re just growing transplants. Something new that is being used are LED bulbs, which can provide light over the full color spectrum but use even less energy than fluorescent bulbs.
Finally, keep in mind that all plants require some darkness, so turn the lights off for at least six hours or more each day.
All plants need fertilizer and there are a lot of ways this can be accomplished, but generally, seedlings don’t require the amount of nutrients a larger plant does. Use some type of water-soluble fertilizer. Start fertilizing after the plants begin growing using a smaller amount – no more than one-half of the general amount recommended on the package – and fertilize maybe two to four times before planting outside.
Thought for the day: “Why try to explain miracles to your kids when you can just have them plant a garden.” —Robert Brault.
Have an idea you’d like Mike to consider writing about? Want more information about these topics? Call the Utah State University Extension Grand County office at 435-259-7558 or email Mike Johnson at email@example.com.