Seed Starting Lessons I Learned the Hard Way

Starting your own seeds can be intimidating for new gardeners, but once you get the hang of it, there’s nothing to fear. One of my goals here on the blog is to provide you with the best information, to help you grow great flowers and hopefully dispel the notion that success is only possible for professionals.

In addition to some of the tips I’m sharing today, I want to make sure you know about a couple other sources of info here on the Floret site:

-In the Floret Resources section, I have created a little Starting Seeds 101 tutorial and photo essay (be sure to click the arrows to advance the images) with some of the basics.

-Here on the blog, you’ll find a post covering Seed Starting Basics.

-In the Floret Shop, I’ve included sowing and growing instructions for dozens of my favorite flowers.

There’s nothing I hate more than seeing trays of beautiful little baby flowers go downhill before my eyes because I overwatered, underwatered, or got too excited about transplanting and didn’t properly harden them off. Seriously, I’ve found some pretty lame ways to waste expensive seed and lots of creative ways to kill baby plants over the years. Learning the hard way isn’t the most fun way to start seeds, so hopefully you can avoid making these same mistakes.

I’ve put together a little list of some Do’s and Don’t when it comes to seed starting. This list of quick tips is meant to complement other resources I’ve already created, plus help you learn from some of my greatest seed starting blunders.

DO tamp down the soil into your containers or cell packs. Then pack it down a teeny bit more. By pressing down on the soil, you not only eliminate air pockets that little rootlets don’t like, but you also make it so much easier to remove your baby plants once they are ready to transplant.   I remember mangling a whole mess of baby snapdragons because I had been sloppy about filling the flats with the soil. When it came time to transplant, instead of popping the plants out with a nice solid chunk of soil attached, the soil separated from the roots and I ended up with a crumbly mess and traumatized plants.  

DON’T forget to moisten the seed starting mix prior to adding your seeds. If you add your seeds to dry potting mix and then try to overhead water, there’s a pretty good chance you’ll send your seeds floating to the corners of the container. If they are really tiny like Iceland poppies or snapdragons, you’ll probably wash them away and have to start over.

DON’T start your seeds too early. In the rush to get growing, it is easy to fall into the trap of starting all your seeds all at once. If you read the seed packets or catalog descriptions, you’ll note that it is recommended to start some slow-growing flowers earlier (10-12 weeks before your last frost) than others (4-6 weeks). If your frost-free date isn’t until mid-May, for example, you’ll want to start your foxglove now, but hold off on fast-growing, heat loving zinnias until later. One year I totally jumped the gun and planted zinnias way too soon and I had plants busting out of their pots, becoming root bound because they had no where to go. They were ready to be transplanted outside, but the spring frosts hadn’t yet passed, so I had to throw them all away.

DO use bottom heat to get your seeds started. It is amazing how much faster and how much better seeds germinate with a little heat at their feet. Propagation mats work great for this. If you are a home gardener or small scale flower farmer you can get by with just one or two mats. Leave your seed starting trays on the heat mat only until they germinate. Once sprouted, move the tray off the heat and make room for the next seed starting tray(s).

DON’T seed more than one type of flower in the tray, especially if you plan to use a humidity dome. Germination rates vary by variety so it is best to have all the cells filled with the same flowers, that way you won’t be forced to remove the dome too soon for a row of early germinators or too late for those slow to germinate. Plus, having variable plant heights in the same tray makes adjusting the height of the lights over the trays difficult (shorter plants within the tray can get leggy when light is adjusted for the taller plants).

DO remove the plastic humidity dome after your seeds germinate. Domes are really only used on the trays until the seeds germinate, which for some varieties may be as few as a few days. Once your plants have popped up, they need lots of air and light. Left on too long, domes can kill seedlings. Note: some gardeners recommend “weaning” their trays from a humidity dome by propping the dome open for a day or two before fully removing it. Similar to the process of hardening off more mature plants, this gradual acclimation to the heat and humidity outside the dome can reduce plant shock.

DO water your plants from the bottom when possible. Standard seed starting sets contain three pieces: a humidity dome, a cell pack layer with drainage holes, and a tray that serves as a liner for the cell packs. By nesting your cell packs (or whatever container you choose to use) in the waterproof tray, you can then add water to the tray which allows the soil to essentially siphon or wick up the water. This keeps water off of your leaves, helps prevent problems with fungus and disease, plus it focuses water where it is needed most, at the root level.

DON’T underestimate the amount of light tiny plants need to grow. If you use grow lights, be sure to adjust them so that they are no more than three inches above the tops of your plants. When I was a newbie, this was not intuitive to me. At all! As a result, I grew lots of gangly, leggy plants because they weren’t getting enough light.The bulbs were simply too far away from the foliage canopy. Once I realized my mistake, I adjusted the lights to about an inch or so above the top of the leaves (it seems really close, but trust me this is better for the plant). Once I had the lights adjusted, I found that the plants grew so much better, with nice strong stems.

DO “harden off” your plants before you transplant them. I am embarrassed to admit just how many plants I fried because I didn’t do this key step. In my excitement to transplant my baby plants into the field, I didn’t give them any chance to acclimate to their new outside environment. “Hardening off” is simply a process of allowing your plants time to gradually adjust to their new environment.

Think about it: your little plants have been in a warm and cozy, temperature-controlled environment for weeks, or months. If you suddenly take them from that space and expose them to bright sun, wind and temperature swings in the open garden, it is stressful to the plant. This step often requires lots of moving plants around, but trust me, transplant shock is real and deadly and taking the time and effort to allow your starts to adjust will make for happier, stronger plants and more flowers.

DON’T beat yourself up if you make mistakes.  Unless you are super lucky or already have a magical green thumb, you’re probably going to make a few mistakes your first time time starting seeds. $#!+ happens. And it’s ok! You’re sure to make far fewer mistakes than I did during the early days, but just know that goofing up is inevitable. That is part of the joy in gardening is learning what systems work well for your situation, your climate.

Have you made any of these same mistakes?  Or do you have any seed starting lessons you learned the hard way? I’d love to hear about them in the comments below.