March is prime seed-starting month for many gardeners. Not only can we direct seed (plant outdoors) some of our cool-season veggie crops like arugula, Asian greens, broad beans, corn salad (mache), collards, kale, peas, spinach, and radishes, but we can also start many of our warm-season crops indoors for transplanting out once the weather warms.
I started a flat of seeds on the weekend, and I thought I’d share the process with you. I did it all indoors, on my coffee table, and managed to make very little mess. Here’s how:
Gather all your necessary ingredients: potting soil or seed-starting mix (a sterile blend of peat or coir, perlite, and vermiculite), a trowel, a large mixing bowl, a watering can, containers (recycled yogurt containers, homemade newspaper pots, or store-bought plastic cell packs), plant tags, and of course, seeds.
I started a variety of seeds, from cool-season crops like broccoli and leeks, to warm-season friends tomatoes, basil, and peppers. Oh, and strawberries. The end of March is a great time to be starting your eggplants, peppers, and tomatoes indoors, as well as most herbs and annual flowers.
Now, before you get all crazy with the soil and the seeding, take a minute to figure out how many containers you’ll sow with each variety, and then make up labels for each. You don’t want to have to do this halfway through with your hands all grubby, or worse, after you’ve finished sowing and can only guess at whether a particular container holds ‘Amish Paste’ or ‘Brandywine’ tomato seeds.
Next, it’s time to make up the soil. Many gardeners create their own special seed-starting blends, but living in a small space, I find it too difficult to wrangle all those different bags of amendments and whatnot. I stick with store-bought seed-starting mix, and it’s just fine. Get out your biggest mixing bowl (don’t worry! The soil is sterile. You’re not going to end up with microbes in your baking) and fill it with the seed-starting mix. Next, add water until the soil feels damp, but not wet. Maintaining a uniform level of moisture (not too much, not too little) can be one of the challenges of indoor seed starting. Pre-moistening the soil before you fill your containers at least allows your seeds to start off on the right foot.
Fill your containers almost to the top, then gently tamp the seed-starting mix down with your fingers, or the bottom of another container. As you can see, I use plastic cell packs rather than recycled yogurt containers or other pots. I find them to be the most space-efficient: an important consideration when you’re trying to squeeze them all under one grow light!
Make a little hole for your seed using a pencil, chopstick, or your baby finger. I usually plant 2 – 4 seeds per container. As a general rule of thumb, seeds are planted to a depth of about twice their diameter. Cover them lightly with soil.
Because you pre-moistened your soil, you won’t need to water right away. And if you have a plastic dome (or even a plastic bag) covering your containers, this will help keep the humidity high and the moisture in. Remove this covering once the seedlings emerge to prevent damping-off (a fungal disease).
Place your seeds near a bright light source. A south-facing window will do, but even better is a proper grow light system that allows you to move the lights up as the plants grow. It’s important to keep your light source 3-4 in. (8 to 10 cm) above the tops of your growing plants so that they do not need to reach for the light and become spindly. If your tray is on a window ledge, rotate it daily.
The other thing to consider is warmth. I use a heat mat similar to this, and it is great for really giving seeds a kick in the pants. Or whatever it is seeds have. Peppers especially seem to love bottom heat.
Finally, because they’ve got to be just a little more needy, you might consider providing your seedlings with some good airflow. Not only will this prevent disease, but it’s also said to improve the strength of spindly stems. Aim a rotating fan (on low setting) at your seedlings for a few hours a day to achieve this.