Every year I start thousands of plants from seed. Except for sunflowers, zinnias and a few others I direct sow outside, everything is started inside under lights in plastic cell packs. I use the same techniques I learned as a home gardener only on a larger scale. In later posts I plan to describe in more detail when and how I start different plants.
If you’re interested in starting a few unusual or expensive annuals or perennials this winter, the following describes the equipment and steps I use to start almost everything I grow.
I use cheap 4 foot fluorescent shop lights you can get from any local hardware. You do not need special bulbs or grow lights, just standard cool white bulbs that will probably come with the fixture. The light fixture is suspended from the ceiling using light weight chains. This will allow you to raise the lights as the plants grow. Connect the fixture to a timer so it will be on 16 hours and then off for 8 hours.
I use plastic cell packs (liners), like the kind used to sell annuals in the spring. You can buy new ones or recycle used ones. If you reuse them, they should be washed in soap and water with a bit of bleach to kill any diseases. The 72 cell per flat liners are big enough for starting most things and you can fit two flats or 144 plants under one light fixture. You may also want to get plastic flats to hold the liners unless you want to have to handle each cell pack individually.
You can either buy or improvise humidity domes. These are clear plastic domes that will fit over a single flat. This will hold moisture in so you will not need to re-water the seeds until they emerge. You can also use plastic wrap or improvise with anything that is clear and will hold in moisture.
Flat, 72 cell liner and humidity dome
Growing Media (“Soil”)
I put “soil” in quotes because I use pre-packaged seed starting mix rather than real soil from outside. I do this because it is light, very well drained and sterile. Most of these mixes are composed of peat moss and vermiculite and/or perlite. If you use dirt from the garden then you must sterilize it by baking it in the oven because it is full of weed seeds and pathogens. If you go this route (I don’t recommend it) find directions on the web about how long to bake your soil and what temperature to use
To avoid compacting the growing media, you want to moisten it by watering from the bottom rather than the top. Fill the liners with grow mix and place them in a container of water. You can use a flat to hold the water if it has no holes. The water will be absorbed through the holes in the bottom of the liners – it will take about 10-30 minutes for the grow mix to become moistened. Once it is wet, remove the liners from the water and allow them to drain for a few minutes.
Sow the Seeds
Now sow the seeds in each cell of the cell packs. Different seeds need to be sown in different ways and you need to rely on the information on the seed package. Typically, very small seeds are just dropped on the surface and are not covered. If this is the case the seed package will say something like “surface sow” or “light needed for germination”. If the seeds are to be covered, the standard rule of thumb is cover with 3 times the depth (smallest dimension) of the seed.
Unless the seed is expensive and I want every possible plant, I usually sow 2 or 3 seeds per cell to ensure I end up with one plant per cell. If the seeds are very tiny, be careful not to sow too many. Under these indoor controlled conditions you will get very high germination and thinning tiny seedlings is very tedious.
After sowing the seed, whether covered or uncovered, use a spray bottle to mist the surface of the soil mix with water. This will ensure that the surface sown seeds are in good contact with the media and that the covered seeds are watered in.
Under the Lights
Cover the flat with the humidity dome and place the flat under the under the lights. The lights should be about an inch above the humidity dome. Most seeds germinate well at normal room temperature, around 65-70 degrees F. Check each day to see if any seedlings have emerged. Once the seedlings are up, prop the humidity dome open for one day and then remove it completely. The lights should be kept around 2-3 inches over the tops of the plants.
You can get plastic liners, flats, growing media, humidity domes and many great seeds at Downtown Home and Garden in Ann Arbor. Altogether it seems like a pretty big investment – light fixture, chains, timer, flats, flat liners, humidity domes, seed starting mix. However, the light fixture, chains and timer will last a very long time, and the flats, liners and humidity domes will last can last 3 or more years if treat them carefully.