Photo courtesy Erica Grivas: Each type of plant you can sow has its preferred germination heat and light conditions, as well as ideal growing and flowering conditions. So you need to know what you’re growing and give it what it likes and when.
Photo courtesy Erica Grivas: Each type of plant you can sow has its preferred germination heat and light conditions, as well as ideal growing and flowering conditions. So you need to know what you’re growing and give it what it likes and when.

It’s the time of year when, if the sun peeks out for more than an hour, gardeners’ fingers start twitching, reaching for their trowels.

There are things to be done, from sweeping squishy, brown former plants off your paths, to planting any new potted plants. There’s a lot that shouldn’t be done yet, like most pruning.

What you want to be thinking about is planning your garden on paper and any indoor seed-starting you are contemplating.

This week, because you might need to order some things before you can play, we’ll discuss seed-starting. If you’re not doing any seeds this year, grab a good garden book or start doodling where you can add some evergreens and flowers for winter interest.

Indoor seed-starting is a fascinating and exacting game, especially here in Seattle. It’s a little like cake baking and a little like betting on racehorses. You need a lot of specific knowledge and a big pinch of faith.

Each type of plant you can sow has its preferred germination heat and light conditions, as well as ideal growing and flowering conditions. Some like to be planted on the surface, some deep, and some with just a dusting of soil welcoming diffuse streams of light. So, you need to know what you’re growing and give it precisely what it likes and when.

Don’t forget the Seattle spring wild card! Seattle’s cool springs mean that if your timing is off, you could have plants bursting their shelves inside while it’s still too chilly to put them outside.

For the highest survival rate, you have to make a good bet as to our average last frost date. The key word there is “average.” No one really knows when frost will hit, especially with the erratic weather patterns trending in recent years.  The first week of May is a time-honored guess, hosting plant sales throughout the state every year — but even that is often too cool for plants that like the soil toasty, like tomatoes, basil, peppers, melons and sunflowers. The last frost date only considers the air temperature, not the soil temperature.

Seasoned players will have already procured heated greenhouses, frost fabric covering their raised beds, and/or red plastic on their soil to hedge their bets when the little plantlings first hit the cold world.

If you want to get your nerd out and do the research, check out the National Garden Association’s last frost date charts and planting guide (https://garden.org/apps/frost-dates/Seattle,%20Washington/) and WSU soil temperature maps (https://weather.wsu.edu/?p=89750) online. Feeling lucky and ready to gamble on putting the plants out in May? Err on the late side for starting your seeds. Count back the seed packet’s specified weeks from your chosen planting-out date, say May 5.

You can try seeds from anywhere, but regional growers like Territorial Seeds, Ed Hume Seeds or Seattle Urban Seed Co., will select and choose plants that grow well here or that have been acclimated to our conditions. Home growers do the same.

That’s where most of our seed varieties come from: generations of farmers and gardeners saving the tastiest, tallest, earliest plants they grew. This only works with “open-pollinated” seed, by the way, not “F-1 hybrids.” Check your packet or do your research on a variety before you save seed. Many grocery produce varieties will not come true from seed.

This year, I’ll be growing seeds saved from my favorite blossoms on the variable calendula Bronze Beauty, in which each flower offers its own riff combining buff, gold, champagne and burgundy. If I did that selectively for six or seven years until my seeds reliably produced the same flower, I could create “Erica’s Bronze Beauty.” Luckily there’s time to think of a better name.

It’s possible not all seeds in your packet will germinate. I like to pre-germinate my seeds to save time and space and prevent watering any duds. It’s also a good way to test the viability of older seeds you may have. I put the seeds in a damp paper towel in a labeled/dated Tupperware or Ziploc bag. Usually you’ll see sprouting in two or three days.

You will want to sow your seeds in “Seedling Mix,” which is far lighter and easier for plantlings to push through than potting soil or mix.

How close to plant your seeds? Depends on your tolerance for thinning (removing runty seedlings), accidental or otherwise. Many people only put two or three seeds in a cell, but tomato expert Craig Lehoullier plants thousands of tomato starts every year by planting densely, say 10 seeds in a cell, and transplanting into bigger pots as needed. There could be some attrition in that process.

A grow light or three is smart, because even a lovely south-facing windowsill may offer weak light in Seattle in winter. To be effective, the lights need to be close to the plants, like within 4 inches, and you’ll need to adjust as the plant grows — that’s why “shop lights” on chains are popular, though for smaller operations, you can use a grow-light bulb in a gooseneck lamp.

Tomatoes and peppers will germinate best in hot temperatures, so a heat mat is helpful for them.  I’ve also heard of people putting them on top of their refrigerator for the heat, but that one didn’t work for me.

As always inside, getting the balance of humidity for plants is tricky. Not enough, your seed tray looks like concrete, too much, and you get the mysterious “damping off” disease, where precious seedlings just kind of melt away. Covering the planting tray with one of those shallow kit lids a.) only works for a minute once the seeds grow, and b.) may be too wet and not allow enough air circulation. A soaking at planting followed by misting the surface a couple of times a day will help.

As to outdoor seeds, a handful of half-hardy annuals (they can take a little cold) can be sown outside in either autumn or early spring, but I would recommend dedicating a protected sunny spot with well-draining soil. Some of these are: calendula, sweet peas, bachelors’ buttons, larkspur and breadseed poppies. Local Floret Farms has some tips, https://www.floretflowers.com/easy-to-grow-hardy-annuals/. Cool-season veggies like arugula, lettuce, chard, spinach and kale are best sown under some cover (such as under hoop houses). Again, check the soil and air temperature needs of your seeds.

All this is not to discourage, but to ensure the best experience growing your first seeds.

Yes, you may have to experiment a bit before you hit your stride, but that’s part of the fun of gardening. There is nothing like the magic of watching a little nugget, which appears as hard and inert as a pebble, transform into a sprout, a seedling and, finally, a stout plant, and then feeling the satisfaction of saving your best-performing seeds and growing them next year.

— Erica Browne Grivas is a Seattle resident and avid gardener with a certificate in landscape design and a national regional director for Garden Communicators International.