Hero Image

News from the Edible Demo Garden

September 2021: Growing Your Own Plant Starts

Stella de Smit, Unsplash
Stella de Smit, Unsplash
The end of the summer is approaching and some of our plants are producing heavy harvests, particularly our summer squash, which are growing in straw bales.  (See our new YouTube video on Straw Bale Gardening.)  We have also cleared some beds and planning has begun for our fall/winter garden.  Some of these plants will be directly seeded into the garden, while others we will start in the farm’s greenhouse.  A planting calendar gives us the information needed to decide when and how to germinate seeds.  (Link to our planting calendar for vegetables and one for herbs.

Growing Your Own Plant Starts

Even with access to a greenhouse, our team is not always successful at producing the number of plant starts that we want.  So, we are paying extra attention to the most important factors that affect germination: sufficient light and warmth, seeding mix composition that provides enough oxygen, and careful watering without disturbing delicate seeds and seedlings. 


Ideal Light and Temperature Conditions for Germination

Seeds germinating
Light:  Light and temperature are important not only after sprouting, but also for some plants like lettuce that need light to stimulate germination.  When planting lettuce, lay the seeds on top of the germinating medium and then cover with a thin layer of fine peat moss or vermiculite so that light can reach the seeds.  Most other summer growing annuals do not need light for germination but many flowers do.

After germination, your plant will need to be moved to a bright, airy location.  A window facing south could provide adequate light although the more fail-safe solution is to use grow lights for about 12-16 hours per day. 

Temperature:  The ideal temperature for seeds to germinate is 65°F-75°F.  If your house is cold, particularly at night, a warming mat may be needed.  However, many gardeners find the top of the refrigerator is perfect for this purpose.


Seed Starter Mix

The ideal seed starter mix is fine and uniform in texture, well-aerated and loose, free of insects, disease organisms, and weeds, and able to hold moisture and drain well. The farm uses a mixture of about two parts aged compost, one part peat moss, and a one part mixture of perlite and vermiculite.  The peat moss and compost are sifted to get a finer medium.  Also, fertilizers like kelp meal and bone meal are added because once seeds germinate, they require feeding in order to grow well. 

If making your own seed starting mix is too much work for you, then there are commercial seed mixes that you can purchase.  Be sure to check the ingredients to determine if fertilizers have been added.  If not, you will need to regularly apply a half-strength solution of a fertilizer like fish emulsion or a liquid fertilizer for houseplants once seedlings emerge. 


Steps for Planting your Seeds
  • Crush any lumps in your mix and then moisten until it feels like a wrung-out sponge. 
  • Fill washed and sterilized (one part bleach to nine parts water) containers to three-fourths of an inch from the top. 
  • Firm mix at the corners and edges so there is a uniform surface.
  • Plant two-three seeds in each unit according to the depth indicated on the seed packet. If no seed packet is available, use the rule of thumb to plant to a depth that is two-four times the diameter of the seed.  
  • After seeds are sown, water using a fine mist spray for small seeds and for larger seeds, use a gentle trickle of water on the surface of the container.  Cover your container loosely (not airtight) with either plastic or a glass sheet.  No further water is needed until seeds have sprouted.
  • Remove cover when first seedlings appear. Lightly water and move your container to the brightest, airy spot you have. 
  • Begin watering regularly when the mix on top feels dry.    
  • Fertilize every other week if your seeding mix does not contain fertilizer.
  • If more than one seed germinates, thin the weaker ones by using scissors to cut the stems.


Stay tuned for next month when we will answer this question:  After you have your starts, what is the process for getting them into your garden?