My go to method for starting seeds has changed over the years, which isn’t shocking. A lot of gardening is learning what works and what doesn’t. For me, I want my methods to work, and to be sustainable. In that the pots will last year after year and not crack. That alone changed most of how we did it.
When I first set out doing market gardening (small scale farming) I got on the bandwagon of using small cell trays, since after all you could grow many plants in a small amount of space. For example, I used 72 cell and as well even went smaller, in the 100+ plus trays. I quickly learned there was a huge flaw. For one, watering was a huge issue – the smaller the growing cell, the quicker they dry out. In a greenhouse, on a sunny day (though not hot), I was often watering 2 to 4 times a day. I just don’t have that time! We also had to water using spray bottles for the smallest cells, not watering cans or hoses. Then, with a small cell you must transplant up quickly. For the smallest cells, that meant a small spoon to pop them out. I was done. I was cracking the cells barely looking at them. It was wasteful and tedious. And I noticed the seedlings didn’t grow as strong. I had to transplant up earlier so they had more soil to grow in.
I had long used 4″ pots for starting strawberry seeds, so I went to that for all our seedlings. What I found is I could plant multiples in the pots, and easily transplant them up when ready (outdoors, in the ground). I can grow 10 onion starts per pot, and 2 to 4 tomato starts (as I transplant these early on into gallon size pots), making this an easy way for plant density, but with the advantage of a larger pot, so they don’t dry out. It’s also a great selling point at market/plant sales, that my starter plants are robust and offer multiple starts per pot.
And yes, Solo Red Cups work great as well. Just use a large bit to drill out a drainage hole in the bottom. You can do 20 a time. Although you have to be careful moving them on trays, as they tend to be slightly unstable. You get used to it though, and you can fit more cups on a 1020 tray as well.
The other area you should invest in is 1020 trays. I use ones with holes if the plants are outside (as they are often in late spring) so they don’t drown if it rains, or for inside, I use standard ones.
The trays allow for keeping your grow area clean, but also make it so you can move the trays around to different areas as needed. Yes, they are not cheap up front. You can get better deals if you have a greenhouse store nearby or buy online directly from greenhouse supply businesses.
Soil…there is a loaded topic. Everyone has what they love. Some wear by sterile starter soil, that is bone dry. Others just use potting soil. Me? I make my own blend. In large quantities. I often have 50 1020 trays going at once. So that is a lot of prep work. I buy Sungro #1 potting mix (which comes in massive bales, and it is super compressed). You soak it first, if you don’t have a tub for it, pick up a cheap concrete mixing tub to do it in. Once it has expanded, I mix it with organic fertilizer (just a bit), and then cut it 50% with G&B organic potting soil. Let that sit a day and get to work filling all those pots up. I hand fill each pot, and shake each pot down to tamp it at bit.
If you want more of a peat moss experience to grow in, I have started using Coconut Coir instead of peat moss.
To Seed: Well, honestly? Follow the seed packet directions. That is the best advice I can give you. Seeds vary by how deep they should be planted. In some cases, like with strawberry seeds, you sprinkle on top and that’s it.
Now then….let’s talk about what I don’t like (I am not opinionated at all, eh?)
Jiffy Pots and similar. The pressed peat and or paper pots that promise to compost into the ground once planted. The problem is: They are expensive, they tend to get funky by transplanting time (if they sit in water), are a one time use, and frankly…it to me impedes root growth once planted. Skip them. Just knock your plant out in your hand, and plant away.
And yes, growing in newspaper pots you make, or toilet paper tubes, or even paperboard egg cartons work, but all are finicky as they will start composting while you are growing in them. They are though great projects for teaching children and often are free to use.
However, yogurt cups and similar are fantastic to upcycle as they last multiple years.