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At its core, starting seed is easy. Get a container, put some dirt in it, give it light & water, and…voilà… seedlings. BUT, there are a few things that can really hinder your success in the seed starting department. Without further ado, here’s what NOT to do:
#1 Grab some old seed out of a bucket in your garage ("hmmm...did I plant that variety in ’06 or ’07… and has a mouse been chewing on this?") and assume it’s going to grow. There’s nothing wrong with using old seed. Some vegetable seed will hold its germination for years and years. But things like fluctuating temperatures, changes in humidity and mouse urine will greatly affect the seed's ability to germinate. If you want to use old seed, test the germination on a few seeds before committing an entire tray to that variety. Here's a great guide on how to easily test seed germ at home-- https://www.highmowingseeds.com/blog/how-to-do-a-quick-germination-test-at-home/
#2 Start your seeds in a plastic container with no drainage holes poked in the bottom. No drainage holes= too much water. Your soil can easily get oversaturated, and the water has no place to go. Seedlings can drown or succumb to the dreaded ‘damping’ off (a horticultural disease or condition, caused by several different pathogens that kill or weaken seeds or seedlings before or after they germinate), which is prevalent in wet and cool conditions. Same goes for overwatering in general. You want the surface of your seed starting media to feel slightly damp to the touch- not soaking wet.
I love these durable seed starting containers: https://allaboutthegarden.com/?sca_ref=3177483.OMdSez9uOx
#3 Start heat loving plants in a cool room with no supplemental bottom heat. Take it from me- this is a sure-fire way to make your tomato seedlings hate you. Yes, they will probably eventually germinate. They may even grow. But they will be slow and weak and spindly. Bottom heat (AKA using a heat mat) is not necessary for all crops. But for heat lovers like tomatoes, peppers, eggplants, melons etc., you will have MUCH faster germination and much happier seedlings with some bottom heat. Soil temps of 70-75 are optimal. If you want to get techy you can get yourself a soil thermometer and check that your soil temps are spot on.
#4 Don’t provide your seedlings with adequate light.
Want weak, leggy seedlings? Not providing your plants with enough light is the way to go.
Seedlings will stretch (put on vigorous top growth searching for light) and become weak and eventually topple over. If caught early, leggy seedlings can sometimes be saved, but it's better to not allow them to become stressed so early in life. Some folks swear by a sunny windowsill, but I’ll stick with my grow lights. I’ve not had reliable success with window light. My go-to now is a is a wide-spectrum, T-5 or T-8 fluorescent tube light. This is mounted on an adjustable stand so that as my seedlings grow, I can keep the lights just a few inches from the tops of the seedlings. Remember that even if you’re using grow lights, if the lights are too far from the tops of the plants this can also cause stretching. Most vegetable seedlings do best with 12+ hrs. of light a day, which you’re not going to get from a windowsill in February in Northern areas.
#5 Don’t provide your seedlings with adequate air circulation. Imagine you’re a seedling. You go from the temperature, humidity-controlled comfort of wherever your human is starting their seeds. You have consistent light, nutrition and water and only the smallest bit of air movement. Suddenly you’re thrust into the real world. You can deal with the changes in light and temperature… but that wind! That’s just too much! Your weak little stem hasn’t been conditioned to any kind of movement, let alone the gusts of the outdoors. You just can’t take it…you topple over and give up… it’s a cruel world. OK, OK, this may be a bit overdramatic, but seriously folks… toughen up those seedlings a bit. At the very least, run your hand gently over the tops of your seedlings several times a day. I usually just put an oscillating fan on low on my seedlings, because I don’t have to think about it, and it helps get them used to air movement. Plus, providing air circulation is another bonus is avoiding damping off.
And a few additional pointers…
Seed starting media- consider what you’re starting your seed in. A light mix with excellent drainage is best. Try my favorite home-made version: https://youtu.be/6hWrdIg7nzQ
Sow your seeds at proper depth- this information will generally be included on the seed packet, but a general rule is twice the depth of the size of the seed itself—so teeny tiny seeds get sown very shallow, larger seeds more deeply.
Use a humidity dome/cover- anything clear that will let light penetrate, yet trap moisture in is ideal. Plastic wrap works fine. The idea is you want to keep humidity levels very high until seeds germinate. Once seeds germinate, remove the cover.
Fertilizer- don’t add fertilizer until seedlings have sprouted their second set of leaves. If you're purchasing seed starting mix, avoid the kind that already has fertilizer mixed in.
Timing- start your seeds so they’re about the right size to transplant when you want to transplant them. This seems like it would go without saying, but if I had a dime for every person I’ve seen with gigantic tomato plants in March, and no where to put them because it’s still too cold in Ohio…
Hardening off- this is the process of gradually acclimate seedlings to outdoor conditions before transplanting them into the garden. DO NOT skip this step. Move your trays of seedling outdoors (best to start on an overcast day or in a slightly shaded location) and let them sit for 4 hours or so, gradually increase the amount of time spent outdoors over the next several days and slowly decreasing the amount of water they receive. This will ensure that when they are transplanted into the garden, they’re tough enough to put up with full sun, wind, and less watering than they had as tender little babies.
