Seed starting basics

Updated: Mar 16

By Aaron French


If you’re at all like me, you’ve recently been daydreaming about growing a lush summer garden. Winter is a great time to reflect on all the amazing produce you grew last year and to get excited about the upcoming growing season. It's also a time to look for something to… up your game. Something to take your gardening experience to the next level.


Might I recommend starting your own seeds? I know, I know...it seems so daunting! You might be asking yourself: “Where would I even start seeds in my apartment?”, “How can I get all the materials?” or “Isn’t that super hard and complicated?”. The answers to all those questions and more are below!



Seed starting is super simple and can be done almost anywhere (sorry, but probably not in your dark basement). Materials wise, all you need are seeds, containers, and propagation media—which is a fancy term for the mixture you plant seeds into. Let's break down each section further:


Seeds: This one’s obvious. You’ll only need to start transplants of vegetable varieties that need an extended growing period. For example, radishes are direct-sown, meaning the seeds are placed directly into the growing area at the time of planting. For a full list of what’s usually grown as a transplant vs direct sown, check out this helpful planting chart from High Mowing Organic Seeds.




Containers: In the industrial greenhouse industry, plastic is pretty standard. The products below are low cost and available from most big box garden centers.



1020 Tray: Named for its rough dimensions (10”x20”), this tray is generally used as support for plug trays, or other smaller-celled containers, like commercial 6 packs. It could also be filled with potting media and seeded directly.




Plug Trays: Often used in conjunction with a 1020 tray, these molded plastic-celled trays are easy to fill, plant, and seed. The number of cells in a tray varies, as does the corresponding size of the cell. A 50-cell plug-tray will have much larger cells than a 128-cell tray. These are often referred to by the number of cells, and 72’s are the most versatile and popular as they’re great for starting everything from lettuce to cauliflower.




Form Trays: Normally used in conjunction with small plastic pots for the purposes of “up-potting” small seedlings. Up-potting is the simple practice of moving a small seedling to a larger container, allowing it to grow more and build a stronger root structure. These form trays come in a variety of sizes, but 32 (spots for pots) are standard.


Pots: Small, molded plastic pots used for up-potting from plug trays. Measured in inches, these pots are perfect for helping vegetable plants reach pre-planting maturity. Make sure to get the size that corresponds with the form tray. 32 celled form trays use 2.5” pots.


Propagation Media: The most important piece in your seed starting journey. Most potting media doesn’t actually contain soil, as they are optimized for germination and shorter-term growth. Instead, they’re mostly made up of peat moss, perlite, and compost. You can buy a prepared mix at most garden centers, or make your own! A great guide for making your own (and choosing a commercial mix) can be found here, courtesy of ATTRA. It’ll help if you get the potting mix thoroughly wet before filling your plug trays or pots. Consistent moisture is crucial for germination and seedling growth, so make sure to keep your young plants quenched!


With these three things, you’re almost set! While seeds don’t actually need light to germinate, they do need a healthy dose of it almost immediately after the radicle (beginning of a root) and epicotyl (beginning of the stem and leaf structure) emerge. A south-facing window or enclosed porch would work great for putting your trays on. A young plant needs approximately 10-12 hours of sunlight a day, so get them there early and make sure to rotate the tray to keep the plants from leaning too much towards the sun in one direction. If you’re lucky enough to have grow-lights as part of your gardening setup, you’ll want to keep them on for around 12 hours a day and generally keep them only a few inches from the tops of your plants.


We don’t quite have space in this post to cover things that can help your seed starting journey become more successful, but look for another post covering some supplemental info on heating mats, fertilization, up-potting, and hardening off!


Here's a little video on how City Sprouts does our seed starting


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