Seed starting in Plastic Containers

I started my lettuce seeds today. I am hoping to transplant them to the garden as soon as my fall crops are spent sometime around Thanksgiving. By starting the seeds now I'll be harvesting my first salad sooner and have a shortened time between harvesting crops. This method of crop rotation is used in smaller gardens, such as my raised bed gardens, and is called succession planting.

I used these plastic containers that had pastries in them to make my mini greenhouses. They can be re used multiple times, but wash them in soapy water between uses to prevent the spread of disease such as damping off. Use a light, loamy seed starting mix or something with loads of vermiculite. You can even use just vermiculite or a mix of vermiculite and peat moss. I fluffed the soil by mixing it in a clean bucket with a small hand rake, and then gently scooped it into the bottom half of the containers until they were filled.

Next I used the edge of a thin piece of cardboard to make little blocks evenly spaced in the soil. This will help with seed spacing and transplanting down the road. If you are using just vermiculite then just make lines and don't worry about trying to get the soil into fluffy cubes. Alternatively, you could use a taller plastic container like the kind lettuce comes in and set newspaper seed pots filled with your seed starting medium inside the container. I strongly recommend this if you are starting something with an aggressive tap root like cucumbers or squash. It will help prevent the roots from becoming tangled.

My containers hold about 20 1inch cubes of soil. In each cube I placed two lettuce seeds right on top of the dirt. (The magenta lettuce tray shown has a higher density of seeds because I let the boys help me plant.)

Use a spray bottle set to a fine mist to soak the top 1/4 inch or so of your soil making sure to get the seeds nice and moist. If you are using a peat/vermiculite mix go a little heavier on the watering.

I then used the tip of my finger to gently press the seeds into the soil (but don't bury them!) to ensure good contact. This helps with germination.

You can just see the tiny sliver shaped lettuce seeds laying in pairs on top of the soil in their little squares. Close up the container and keep it in a location with even temperature and out of direct sunlight.

I keep my containers on a back corner of my kitchen counter. This may not work for everyone though depending on the temperature of your home and time of year. You can check the temperature of your soil with an instant read thermometer like a digital one used for cooking meat to make sure you are hitting the ideal sprouting temperature for your seeds. Lettuce likes a cooler soil in the 60-70 degree range with the optimum sprouting temperature being 68 degrees Fahrenheit.

I like to check Johnny's Seeds for the temperature range I should shoot for.

This is the optimum range chart Johnny's provides on their site for sprouting Magenta Lettuce. You can see that the seeds really don't sprout as well outside of 60-77 degrees.

Some seeds like Peppers really need the heat to sprout.

This chart from Johnny's shows that pepper seeds like a temperature range of 80-90 degrees F to germinate well. I can usually hit this temperature by sticking them in the top shelf of the closet where my hot water heater is or by using a heating mat. I actually just use a medical type heating pad like you would use if your back was sore. I sandwhich it between a folded towel with my mini seed greenhouses set right on top. I turn it on low and then check the soil temperature in an hour to see if it has hit the optimum range. If need be, I will turn it on medium, but that's not usually necessary. My heating pad has an automatic shutoff after about 30min, but because the lid on the container stays closed it traps the heat and I only need to turn the heating pad on every four hours or so.

Even temperature and moisture will give you the most success with getting your seeds to sprout.

Next time, I'll give some tips on caring for your seeds once they do sprout and talk about thinning out and lighting requirements.