The other day I talked about when to start seeds indoors. But how do you do it? I know that can seem like a no-brainer, but some people have simply never done it! Or perhaps haven’t done it since they were young and can’t remember everything the adults were doing. If you’re one of those people, I don’t want you to feel bad. And I don’t want you to give up on starting a garden from seeds. We’re going to talk about how to start seeds indoors.
I’m using these this year. They’re pretty much what you’d buy seedlings in at a store or nursery.
In fact, many stores with a garden center will have a pile of their empty, used plant containers somewhere. Since they’re often destined for the garbage, you can often ask an employee and take a bunch home with you for free! You’ll just want to sanitize them before reusing, in case of plant diseases or pesticides you don’t want your plants exposed to. Most of my bigger containers are the ones my mom and I have saved after buying plants at nurseries over the years.
Others like peat containers, as they can go straight into the soil with the plant when its time to transplant.
You can also get creative. People use yogurt and other dairy-type containers with a hole punched in the bottom, egg cartons, and really anything with sufficient draining capabilities and room for a baby plant. Just make sure it’s clean of food or anything else that may hurt a seedling.
I would also recommend getting trays to set the planters in, with enough of a lip that you can pour water in. This allows for bottom watering.
Seed starting mix is technically soiless. It uses coconut coir or peat in place of dirt, usually. It’s also sterile to protect the fragile seeds, and doesn’t really have any nutrients. There’s lots of tutorials out there on making your own. If you use this, you probably need to soak it in water (like in a bucket) and then squeeze out excess water when you transfer it into the pots.
I honestly have just been using potting soil. I know I’m not the only gardener out there who does. An organic soil is my go-to. This year I’ve sprinkled cinnamon on top too, because it’s supposed to help inhibit damping off disease. It’s a fungal disease that usually kills plants, and is almost exclusive to seedlings started indoors. I lost a ton of my indoor seedlings last year because of it. Potting mix shouldn’t have to be soaked first, but it does need to be damp before planting.
Lights and Temperature
A south facing window isn’t always enough to get vigorous seedlings. Adding some lights and even heat and moving air can help grow much stronger plants.
Windows often block out part of the light spectrum, so get a full spectrum bulb or a grow light to ensure that the plants get those missing parts of the spectrum. They’re important. Many people just use shop lamps with fluorescent bulbs. The light shouldn’t be far from the seedlings; if need be, put it closer when they’re germinating and raise it when they’re getting bigger.
Most plants require a minimum soil temperature to germinate and thrive. An easy way to ensure this without raising the temperature of the whole room (and your heating bill) is to get heat mats made for seed starting. These can be placed directly under the seed trays to add some warmth. If you’re set up is somewhere indoors where the temperature is probably in the sixties, the few degrees added by a heat mat will make all the difference for the warmth-loving plants like tomatoes and peppers.
Some people also turn on a a small fan to blow on the seedlings. It’s supposed to make the seedlings more vigorous, and perhaps even lessen the chances of damping off disease. You don’t want to create a gale for the babies; more like a breeze. A smaller fan on a low setting is best.
Seed packets with have simple instructions on how to plant a seed. Every seed is different in how deep it needs to be planted. Usually the bigger the seed, the deeper it can go. Pumpkin seeds, for instance, can be planted a good half in down–about the same size as the seed itself. Others–usually the tiniest ones–should be surface sown. That simply means that you place a few seeds on the surface of the soil, without covering with dirt.
Why is this? Well, every seed has a certain amount of energy and strength to push up through dirt. The bigger the seed, the more there is. If a seed is planted too deep, it will die from lack of sunlight before it ever pushes through the surface.
If you have seeds with no instructions, plant the seed at about the depth of the length of the seed. This means that the tiniest seeds should be surface sown or barely covered with the merest sprinkle of dirt, and bigger seeds can be sown 1/8th inch, 1/4th inch, or even 1/2 inch deep depending on their size.
Make sure to label your containers to know what you planted in them. This is especially important if you plant more than one variety of the same kind of vegetable.
Why? Well, once you get them out in the garden you label or chart what was planted where. Then when you harvest them, you know whether you liked the Yaya or Resistafly carrots more. You can note in your garden journal favorite tastes, more disease- and pest-resistant varieties, and more. That way you know, as the years go on, which varieties you want in your garden and which you don’t.
It also helps so you’re not playing a guessing game when it’s time to transplant and you need to organize your garden. Some plants do badly if planted next to each other–they attract the same pests, they feed heavily on the same nutrients, etc. Others are big and would shade out smaller plants if put in the wrong place. And all have ideal spacing requirements for optimal growth. If you’re brand new to this and can’t tell broccoli from squash from tomato, you’re going to have a hard time if you don’t know what’s what.
The best way to water seedlings is bottom watering. This is where there’s a hole in the bottom of the planter, and the planter is set in a tray. Water is poured into the tray, and the soil wicks it up. This helps minimize the risk of damping off disease and other problems caused by watering directly on the plants. Some plants plants like tomatoes simply don’t do well with wet leaves and stems their whole lives.
Soil should remain moist pretty constantly, but it shouldn’t be soaked. Let the water in the tray dry up before refilling, but don’t let the seedlings dry out totally. As they get bigger, it’ll be okay for them to dry out a bit. Most plants do better being watered deeply once or twice a week instead of being constantly wet once they’re bigger. You’ll start this transition when they’re getting close to transplant time.
Seed starting mixes have no nutrients in them. Many potting mixes have at least a little in the soil and may also have some added in to feed plants. If you’re using a potting mix with nutrients added in, you may get away with not fertilizing at all.
I’d recommend fertilizing about once a month from the time they pop up until they’re transplanted. The first feeding can be delayed if they’re in a potting mix. If they’re in a seed starting mix they’ll need it sooner and possibly more often to thrive.
Fish emulsion is probably you’re best bet, although any water-soluble fertilizer will work. Just add the recommended amount into the water before watering and you’re good to go!
It is possible to over-fertilize, so don’t go crazy. If the seedlings seem to be doing less-than-great, give them a little. Never use more than the recommended amount of fertilizer in a single feeding.