When to start planting seeds indoors? Check your frost date

• Published date: 08 February 2022
• Publication title: The China Post

February marks the midpoint of winter, and with spring just over the horizon, many gardeners are dreaming of sunny days and dirty fingernails. For those looking to get a jump on the growing season, starting seeds indoors offers the most gratifying - and productive - option.

Before digging in, however, it's imperative to know exactly when to start, which means finding the last average frost date in your area. Consulting with your county's cooperative extension office should arm you with hyper-local guidance. Absent that, there are some good online calculators that will get you close.

I like the one provided by The National Gardening Bureau (https://garden.org/apps/frost-dates/). To use it, plug in your zip code and take note of the date in the field where the '10%' column intersects with the 'Last 36-Degree' row. That represents the date when on average, there is only a 10 percent chance the temperature will drop below 36 degrees, meaning outdoor transplantation is a safe gamble.

Armed with the scientific knowledge that water freezes at 32 degrees, some will lament my conservative recommendation. They may even point to years past when they've successfully transplanted tender seedlings outdoors weeks earlier. But as someone who has been burned by a late frost, I'm here to tell you that patience is key. Remember, those dates are averages, and temperature extremes can fluctuate wildly from year to year, past luck notwithstanding.

Those gardening in horticultural zones higher than 9 can ignore this advice, as the southernmost parts of the continental U.S., as well as Puerto Rico and Hawaii, are considered frost-free (there, it's the heat of spring and summer that should be avoided.)

The rest of us will need to do some math. Seed packets typically advise that seeds be started a set number of weeks before the last frost. After calculating your start date, which will be unique for each seed type, it's important to respect it. Start too soon, and plants likely will grow weak and struggle to thrive; start too late, and your harvest will be delayed, sometimes even inhibited from reaching its full potential.

While you're waiting, obtain and prepare appropriate containers, which include multi-cell plug trays, individual biodegradable pots and recycled plastic yogurt containers. Each should have a drainage hole poked in its bottom. If planning to reuse last year's vessels, be sure to disinfect them with a solution made by combining nine parts of water with ten parts of...