20 May Germination 101
Here in northern Michigan – Zone 4b, to be exact – we can’t wait for summer to come to us. We start our summer early in heated hoop houses in order to give our plants enough time to produce the desired fruits, vegetables and flowers. There are very few things I direct seed; I prefer a controlled plant nursery to the vagaries of the great white north weather.
Successful seed starting can seem like magic, and in a way, it is! It never ceases to amaze me that all of the instructions to produce a plant are contained in a tiny seed. When I first started growing from seed, it seemed like sometimes one thing would work and other times it wouldn’t. It was frustrating to say the least. Over time, you can get a sense of what works, especially if you keep notes or records of some sort. I wish I did a better job of that! In general, though, there are some generalizations that make things easier.
Overall, I would say vegetable seeds are easy to germinate, but some flowers can be tough. For one, many flower seeds are tiny – amazingly so – and delicate. Also many flower seeds respond to an extended cold period or fluctuating temperatures. Imitating Mother Nature can work… for example, flowers like larkspur, bupleurum, Bells of Ireland, campanulas, snapdragons and nigella like a cold chill (a couple of weeks in the fridge or cooler) help jump start the germination process. I sometimes start these in soil blocks and then put them under my greenhouse tables (think cold) or our walk -in cooler (39 degrees F)
One thing that also works is fluctuating day/night temperatures. I tried unsuccessfully for two years to try to germinate verbena bonariensis. Finally, I paid attention to the seed packet and put them in the germ chamber during the day and under the greenhouse table at night. It took a while bit IT WORKED!
Which leads me to the next piece of advice – PATIENCE! Many seeds can take a few weeks (or more) to germinate. Don’t give up! Many times, I have been tempted to compost seed trays, only to come back the next day to see that they’d started! In my experience, vegetable seeds are predictable but flower seeds are often recalcitrant!
In general, there are several good rules of thumb:
Pay attention to seed packet instructions! Planting depth, germination temperature and time, etc is valuable. I make a spreadsheet of this information for easy reference.
Optimal germination temp = optimal grow temp + 10 degrees F. Remove from heat once 50% of seeds have germinated.
Keeping the soil surface moist and humid is important. Don’t let the soil become too crusty. For really small seeds (like many flowers) water from the bottom so you don’t dislodge the seeds.
Having a germination chamber is a real game changer! There are many plans online that are inexpensive and effective. We enclosed a Home Depot shelf (turned on its side) with 2″ foam board. The shelves are made of 1/2″ PVC. We have a 10 gallon trough from Tractor Supply that’s heated by a livestock water heating element and controlled by an Inkbird
thermostat. Crude and cheap, but it works!
Planting seeds too deep or having the soil surface dry out are two major reasons for low seed germination.
Once 50% of the seeds have germinated, move those babies into the light. I use both grow lights and heated hoop house benches. Bottom water if possible. Young seedlings can be susceptible to damping off, so letting them dry out a bit between waterings is important.
- Introduce stresses (e.g. wind and direct sun) gradually and one at a time when hardening off your starts.
- Using a grow light? Get it close to the soil for healthier starts.