Early Edibles: Seed-Starting With Bill Thorness

Are you raring to get the edibles growing for this year’s garden? A lot of us are, as evidenced by the full room of eager gardeners at my talk at Swansons Nursery last Saturday. From the class questions and discussion, here are a few tips to get growing now.

Starting on a Heat Mat

If you have an indoor seed-starting station, or a warm location with a sunny window, you could be starting some vegetables soon.

In mid-January I often start a flat of salad greens – lettuce, Asian mustards, spinach, etc. This can give you a head start on planting.

The basic seed-starting station has a seedling heat mat, which sits under a multi-celled seedling tray. Into each of those cells you put moistened seed-starting soil mix, then sprinkle seeds and get it well-watered. A clear plastic shell goes over the top of the tray, which holds the moisture in while the seeds are sprouting.

Keep an eye on the soil to make sure it doesn’t dry out, because inconsistent watering is often the cause of lower germination rates or straggly plants.

With the bottom heat, seeds will sprout in a week or less.

Adding Light

Once the seedlings are up, you can move the tray off the bottom heat (and start another tray of seeds on it). The sprouted seedlings now need a lot of light to grow healthy and strong. Our short days mean that even a sunny, south-facing window may not be enough.

I use a basic fluorescent shop light, suspended on chains just a few inches above the plastic top of the tray. I put it on a timer, and keep the lights on 10-12 hours a day. Keep moving the light up as the seedlings grow, and in a few weeks they will be ready to “harden off” and plant outside.

Harden the plants by setting them outside for lengthening periods of time over the course of a week, starting with an hour the first day. This gets them used to the wind and variable temperatures.

Use Season Extension

If you started growing lettuce from seed in mid-January, you’d be ready to plant it out in mid-February. The weather is still too cold and rainy to just put them in open ground. You’ll need some sort of “season extension” device. This is a cloche or a cold frame that will cover and protect your young plants.

A cloche is a “hoop house” with steel, plastic or fiberglass hoops in a tunnel shape and sheet plastic stretched over it. A cold frame is a hard-sided box, usually with a glass lid (often made from a recycled window sash). There are commercial types available, or you can make your own.

With season extension (and a daily patrol for slugs and snails), you can keep those starts growing, and you’ll be eating salad from your garden by mid-March.

Practice Succession Planting

One final tip, courtesy of our second U.S. president: Thomas Jefferson, in his published garden journal, advised people to plant a thimbleful of lettuce each Monday. That would ensure a continual supply.

That might be a lot for us, but if you practice that type of “succession planting,” you could be eating salads all through spring.

Bill Thorness is a Seattle garden writer and speaker. The author of two gardening books, Cool Season Gardener and Edible Heirlooms, he blogs at www.coolseasongardener.com.

Editor's note: Swansons is proud to carry both of Bill's excellent books.