The Nurturing Heat

Most seedlings germinate best with bottom heat ranging from 60 to 72 degrees. The best way to get this consistency is to set up a commercial seed-starting heating mat underneath your trays or pots—these keep temperatures about 15 degrees above room temperature. At Portland Nursery (, Hydrofarm Seedling Heat Mats sell for about $30 for a single-flat size, $50 for a two-flat size, and $80 for a four-flat size. If you’d prefer to skip this step, choose a nook in your house that will provide a fairly consistent temperature. The top of your refrigerator can be an excellent place to start those flats of seeds that germinate best in warmth.

Inch by Inch, Row by Row

Commercial soil-free seed-starting mix is available at most retail nurseries or in large bags at Portland’s Concentrates Inc ( The mix is a bit more spendy than regular potting soil, but it offers better moisture retention and a finer texture. Plus, it’s sterile, so it’s less prone to mold and disease. Moisten your seed-starting mix in a large bowl or bucket and gently scoop the damp soil into your pots or flats to a 2-inch depth, being careful not to compact it too much.

Set up your labels before sowing seeds, and stick rigorously to the procedure to keep track of what you’ve sown. Popsicle sticks will work, or you can purchase wood, metal, or plastic labels. Use a pencil (markers will fade in sunlight) to mark each label with the seed’s complete name and the date it’s sown. Once the labels are in place, sow your seeds according to the depth indicated on the seed packets. It is crucial to start each type at the proper time, so that the plants are neither too large to manage indoors before setting out nor too small to survive outdoors.