This is what I do.
Clean pots are a must, whether they are new or old, they must be clean. Nasty organisms that will kill your seedlings can hang out on uncleaned pots for years.
Your mix to start your seedlings is also very important. I used to mix my own and thought that was the best way to go, until I tried Pro-Mix. This just makes seed starting so much easier.
What pots to use? I use a 3 1/4" x 3 1/4" x 3 1/2" (deep) plastic pot. Or 85cm x 85cm x 90cm (deep). I prefer this size, they fit well into trays, 18 per tray, and deep enough for most seedlings to develop a good set of roots. Pictured below are a mix of what I use. The larger square ones are for seed starting, the small square ones I use for oxalis or cyclamen bulbs. The round ones are used for small bulbs (I'll blog on that another time).
I usually get a bit of an assembly line going when it comes to seed starting. I fill my Rubbermaid bin (56l) with Pro-Mix, have my pots on hand and my trays. Oh yes, can not forget my gravel topping and we'll discuss this more later in the blog.
I've gone through my Pro-Mix as I've put it in the bin, breaking up the clumps and taking out any sticks and twigs present. It's much easier to fill my pots after I've done this. I fill my pot about 3/4 full of the mix and using another pot I tamp the mix down. I keep doing this until I have a couple of trays full. I guess it depends on how much seed you have to sow. Once that is done I ready my tags and seed envelopes.
Tags are a matter of preference as well. Some use popsicle sticks, old cut up window blinds, purchased plastic tags, what ever works for you. I use these.
Marking the tag, I use a HB pencil. It stays on better than any permanent marker I've used to date. It does not fade nor does it wash off. It erases off quite well after being washed. I mark my tag with the name of the seed and the date it was sown. Why the date, some seeds take longer than others!
I write down the info on the tag and place it in the pot on one edge. Then I sow my seed on top of the tamped down mix. I place the pot with sown seed back in the tray. On to the next pot. Oh, hang on, I've just sown Seseli and I know that that seed requires light to germinate. I take my tag out again and mark the end with a colored marker. This is just to let me know that I should not cover the seed. I'm trying to be quite general and yet specific, if that makes any sense at all!! Each seed has different requirements, you learn what they are as you go along. You develop a system that works best for you.
I now have a full tray of seed sown pots, now what. This is where the gravel topping comes in. Why the gravel? I questioned that at one time as well. The gravel stops the seed from floating when watered in, it stops mold and other ucky growths from growing on top of your seeds and pots. It makes watering your pots so much easier as it acts as a buffer / filter for the water to seep down and not disturb the placement of your seeds. It just works!
I purchased 80lb bags of #2 granite grit (for chickens) from a feed store for quite some time at $8 per bag, and then I went to my local gravel yard. I filled up a 100 litre bin with 7 mm gravel for $3-5. A matter of preference again. I still buy the granite grit and use it as a topper when sowing my cyclamen seeds, I'm sure the 7 mm gravel would work just as well, just a preference. I'm sure when I run out of the granite grit I'll go to using the gravel, as I haven't found a source for the grit in Red Deer yet. No big deal.
The top of each seed sown pot gets a layer of gravel. Usually about 1/4" per pot. Now keep in mind what your seeds requirements are. Seseli as I mentioned before will not get covered. I treat Aquilegia seed a bit differently as well. For that I ready my pot, put down my layer of gravel and then sprinkle the seed on top of the gravel. Generally, it is mix, seed, gravel though.
If you're going to be starting a great deal of seed, you've found that you've developed an addiction to seed starting, get yourself some good books that you can reference, have your reference materials on hand so that you can quickly look it up and get back to your seed sowing.
What next? Water, of course. Your trays are filled with seed sown pots and they want a good drink. Again, there are different ways of doing this. I put my seed sown pots in a water tight tray and fill the bottom of that tray with water and let the pots soak it up. I keep doing this until I'm sure the pots are well watered. Or, I place the pots in mesh bottomed trays and a hose on the mist or shower setting I water the pots in well. I've placed my gravel on top of the pots of seed, I'm not worried about my seed going anywhere. My preference depends on how many trays I have to do, how much time, and how much energy I have.
And lastly, what do you with these seed sown pots? Cold frames! When I think of the years I started all my seeds in the basement, I shudder.
I love my cold frames. I had left my cold frames with the last house, just too big and cumbersome to move, or take apart, or,,, at any rate, they got left. They are just too easy to build though, any one can do it. I'll post another blog on how to build / create a cold frame. But back to starting seeds.
The trays of pots get a good drink and then are placed into the cold frame. Soon, before you know it, you'll have a frame full of wonderful seedlings.