Success with seed starting
Lavender seedling
Do you feel intimidated by the thought of starting plants from seed? I totally understand! Even though I’m writing a post about successful seed starting tips, I still fail at one crop or another each year. There is always something to learn, which I think is why my perfectionist nature loves the challenge. Even though there are lots of nuances to getting great germination there are some basic things to understand about what seeds need. Once you know these, your rate of green seedlings versus sad, empty soil blocks will steadily increase.
Start with a professional soil mix As much as I love to DIY and use as little plastic as possible in my business, a sterile seed starting mix is necessary to get your little plants off to a good start. It’s also impractical for most of us in Canada to have access to good garden dirt and compost in late winter when seeds need to be started. I save some compost in a big bin each fall to add to my soil blocking mix once my plants need to be bumped up to a bigger container but I don’t use it for starting seeds. The risk is that pathogens in your soil or compost will cause damping off, a condition where seeds or seedlings are killed off suddenly. I use a Promix blend that is readily available at hardware stores and can be ordered in a large bale to reduce the amount of plastic bags necessary. If you are concerned about the use of peat in seed starting mixes like I am, there are more choices coming on the market every year, depending where you live. Coir is one substitute but there are exciting developments right here in Alberta using crop wastes. Keep checking your garden supply stores and asking for peat free mixes so suppliers know it’s important to consumers.
Moisture Seeds can’t sprout without a lot of moisture. I see this every year in my field, when I’ve direct sown a crop into what I think is nice moist soil, only to wait weeks and not see a single sprout. One good rain and boom! Seedlings seem to pop up overnight. When I make my soil blocks, my potting mix has the consistency of wet cement. There is usually a little bit of water pooling on top, which tells me I’ve got the right amount of moisture. Don’t skimp on the water! Similarly, you need to keep that soil wet during the germination process. I cover my soil block trays with a humidity dome to keep the water from evaporating off while the seed germinates. A plastic bag around the whole tray also works. Depending on the variety being germinated, I might use vermiculite to cover the seed, which also holds moisture next to the seed. Some seeds don’t like to be covered though, which brings me to….
Light or darkness Some seeds need to be sown on the surface of the soil so they will receive light to stimulate germination. Others need to be covered by soil because they require darkness to germinate. If your seed package doesn’t tell you what kind of treatment your seed prefers, you should Google to find what is called the culture sheet from the seed company. These culture sheets are a goldmine of information and I always read them before I try a new variety. Regardless of light or dark, make sure your seed is in good contact with the soil. If not, it may sprout and send it’s roots sideways or up, promptly killing itself, instead of sending the root down into the soil block. When I work with really tiny seed, I use a toothpick to pick up and place each seed on the soil surface, giving it a little pressure so it’s firmly sitting, but not sunk into the soil block. Painstaking, yes! Worth it though to avoid wasted seed that doesn’t germinate.
Temperature Along with moisture, this is a really important variable in getting good germination. Most annuals aren’t too fussy and will germinate well at room temperature of 20C. Some, like lisianthus, do much better with some added heat. I have commercial heat mats for those crops that prefer temperatures closer to 24C but have also used a regular heating pad in a pinch. A lot of what are classified as “cold hardy annuals” will germinate at temperatures as low as 10C. I germinate lupins at in my cool garage at that temperature. I always have a digital thermometer on my seed starting racks so I know exactly what the temperature is under the lights. I use LED lights now because they don’t give off much heat and save energy. If you are using standard lights, they can change the soil temperature quite a bit and prevent cool temp loving seeds from germinating. Perennials can be tricky to germinate as some of them require what is called cold stratification. This is a long period of alternating warm and cold temperatures to mimic what the seed would get through winter. This fluctuation, while keeping the seed in moist soil, softens and breaks down the hard seed coat and allows the little sprout to emerge. I’ve had some success alternating trays between my fridge and a warm room. Winter sowing is another way to accomplish this, where seeds are sown in late fall/early winter indoors, then put outdoors for the rest of the winter to go through the many freeze and thaws of our winters. Some of these perennial crops still elude me and I definitely am not an expert on cold stratification. If I get 50% germination on some of these trickier crops, I consider that a huge win.
It’s not you, it’s the seed Sometimes, despite my best efforts, nothing works. This is always frustrating to me and sends me back on a research binge to see what I might have missed in understanding what conditions this seed needs to perform best. I always tell myself “plants want to live”. It’s their biological destiny, to flower and reproduce, so even when I fail to give them ideal conditions, a few plants still thrive. Some varieties just have lower germination rates, and I buy from companies like Johnny’s Seed that list expected germination rates on their packaging so I can account for that in my planning. It’s reassuring to know that even the seed company doesn’t expect more than 60% germination from some plants. The other important variable is the age of the seeds. Fresh seed gives better germination in most cases and dramatically so in certain varieties. If you are using seed from previous years, do a quick germination test with it before sowing a whole tray. I put seed in between a wet hankerchief (you can use paper towel but I don’t have that in my house) and then seal it in a glass lock container. I leave it at room temperature for 5-7 days. If I don’t see little sprouts starting on a good percentage of seeds, I toss the package.
Next time I’ll talk about caring for those little seedlings once they sprout to make sure you have healthy plants to put in the ground!