So you want to know how to grow on your seedlings, you say? Or you planted them a bit too early for your last frost date and they're too big for their original pots?
I can help.
There are a few key pieces of equipment that will help you produce strong seedlings.
You can use almost anything as a pot: yogurt containers, soda bottles, egg cartons, those plastic bubbles that Costco sells apples in, or actual pots. Feel free to experiment. You can get a bunch of used pots for free from gardening centers if you ask, or bug your green fingered friends (or the friends with black thumbs - they'll probably have plenty of empty pots). They probably have piles of them sitting around. Just clean them out with a 10% peroxide solution (or bleach, but peroxide is nicer to the environment and your lungs) to kill anything left over from the previous plants and soil that were in there.
You'll thank yourself later for printing up labels now. Trust me.
Moistened potting soil. Not too wet, mind you, just a little damp so it will take up water easily when you're watering instead of repelling it as dry peat moss normally does. And no, dirt from your backyard isn't a good idea for your tender seedlings. You need soil that is going to both retain water and drain well, providing a good temporary home for your plants. They'll go into the backyard soil just as soon as you've hardened them off.
I use 4' long shop lights with both warm and cool fluorescent bulbs in them. The mix of lightbulbs gives a good approximation of full spectrum light, like sunlight. It's also a whole lot cheaper than growlight bulbs. I have them plugged into a power strip which is plugged into an automatic timer that keeps the lights running for 16 hours per day.
The fan, you see, is key to avoiding spindly plants. Otherwise they end up looking like this:
Not so pretty, eh?
The fan, you see, is the secret. Out in nature, plants are constantly blown about by the wind which keeps them shorter and stockier than you can grow them indoors under lights. The fan imitates the wind and keeps all of your plants happier.
That broccoli above? Not so happy. It sprang up faster than all the rest of the plants in that tray, so it didn't get exposed to the fan soon enough. This is also why you should plant seeds that like the same growing conditions and spring up at the same time. Do I ever remember to do this myself?
Say you're like me and you have started more plants than you have sense and you mixed them together in the same container.
Well, after they've sprung up and put on their first set of true leaves, you'll need to pot them up and let them grow on. Unless you're like me, of course, and you get so busy that by the time you turn around again, they've got 2 or 3 sets of true leaves.
1. Fill your pot halfway with moistened potting soil.
2. Using a dibbler, pencil, fork, spoon or letter opener (my personal favorite), pry your tiny seedling out of the soil and untangle its roots from those of the plants around it.
Be gentle. This part is tricky and since I can't photograph myself doing something that takes two hands, you'll just have to imagine it.
3. Holding your plant by a leaf, not the stem, lower it into the pot and hold it at the level you want to fill soil around.
Since this is a tomato and they grow roots all along their stems, I like to put them in as deeply as I can. This also deals with any spindly stems I might have and will give me a stronger plant in the long run. More roots = stronger plant. Other plants should be planted at the same depth they were growing at originally.
4. Fill the soil around your plant and tap it sharply on the work surface to settle the soil, then fill in with a little more soil. When you're done, press down the soil to firm the plant in.
5. Now that your plant is potted up, be sure to label it before you move on to the next one. Trust me, you'll forget in an instant which variety you were last working on and then you'll be bummed to have a pile of mystery tomatoes sitting around.
Ask me how I know.
6. Finally, after all that your seedling has been through, it needs a nice drink. Now is a good time to feed a diluted liquid fertilizer to your seedlings. Water from below so that you don't wash it out of its new home. Your plant will thank you.
7. Set the new tray of plants together under lights and make sure your fan is on and directly blowing across your plants. I like to plug my fan into the same timer the plants are on, although you could leave it running 24 hours a day. I find that dries my plants out a little too quickly, though.
A week later, they'll probably look something like this.
8. Grow them on until you've reached the proper planting out date for your area. Hot season plants usually like to go outside either right after the last frost date (Here in Colorado, that's supposed to be May 15th, but I usually wait until the weather forecast shows nighttime temperatures staying above 50 degrees at night.) or two weeks later. You don't want all of your hard work to be killed by a sudden cold front, do you?
I didn't think so!
9. Don't forget to harden off your plants before just leaving them outside for the rest of the season. Otherwise, you'll crisp them and then you'll be sad. As will your plants.
It really is that simple (it's not difficult, it's time consuming) to start your own plants from seed and then to prick them out and pot them up. It's a lot cheaper than buying plants from the store* and you get to choose all of the different varieties instead of having to accept whatever is currently being sold.
This way, however, lies the siren song of tomatoes and once you start growing your own plants successfully, you may discover that you have a hard time walking away from the seed racks in spring. Soon you'll discover yourself wanting to try just one more tomato variety and you'll start looking forward to those sexy, sexy seed catalogs that arrive in February.
Ready? Go for it! You know you wanna!
* Well...eventually it will be, if you bought all of the different gear I suggested. If you did it all on the cheap, or had a lot of this stuff laying around and you're really into gardening, it totally pays to raise your own plants. Otherwise, think of it as doing your part to save the Earth on your little patch of land. Life is better with more plants in it.