Gardening has seen a huge resurgence as more Americans are discovering their green thumbs. Between 2008 and 2013, gardening in the U.S. climbed to its highest levels in more than a decade, according to The National Gardening Association. Today, one in three households grow food, and it’s not just "older" Americans who are doing it. The most significant increase in gardening is in younger U.S. households.

The bounty produced by these gardens is so plentiful, another old custom has resurfaced: canning food.

Home canning involves preserving fruits, vegetables and even some meats and fish using a heating process that seals food inside air-tight jars. About one in five American households can food, and 63 percent of those jar their own vegetables, according to the Centers for Disease Control and Prevention (CDC).

Food In Jars blogger Marisa McClellan, who has published two books on canning — “Food in Jars: Preserving in Small Batches Year-Round” and “Preserving by the Pint” — says the growth was brought about by the organic food movement and people wanting to connect with the past, when preserving was an essential part of American life.

But people new to canning should realize it’s not without risks. The most serious threat is botulism, a potentially deadly illness caused by a bacterium found in soil that can thrive inside a sealed jar. Other dangers come from poor sterilization techniques, not using recipes deemed safe for canning and careless maintenance of canning equipment, especially pressure canners.

Home-canned vegetables are the most common cause of botulism outbreaks in the nation, according to the CDC. From 1996 to 2008, there were 116 outbreaks of foodborne botulism reported — 48 caused by home-prepared foods and 18 from home-canned vegetables.

For first-time canners, “the greatest learning curve is coming to the understanding that they can't do whatever they want,” says McClellan. “With cooking, you can add a little dash of this and that — but that doesn’t always work with preserving. Unfortunately with canning, because recipes have to maintain a certain acid level to be safe, adding the wrong thing can render a recipe unsafe.”

Following Grandma’s old recipe book from the 1950s may not be a wise idea, says McClellan, since we know much more about safe food preservation today. Instead, use a modern recipe from a reliable source and follow the manufacturer’s directions if you’re using a pressure canner.

Also brush up on these basics:

Low-acid vs. high-acid foods

There are two main ways to can food: hot water bathing and pressure canning. The technique you use depends on the type of food you want to preserve.

Certain foods are high in acids, including many fruits, jams, jellies, salsas, tomatoes with added acid, pickles, relishes, chutneys, sauces, vinegars and condiments. These foods can be prepared and jarred in sterilized containers and then inserted into a water bath canner (or large pot) with boiling water. The heating process, combined with the acid content in the food, kills bacteria and prevents botulism.

Low-acid foods, including some vegetables, soups, stews, stocks, meats, poultry and even some seafood, require a pressure canner. This is a specially designed pot that uses a pressure weight to heat the contents up to 240 degrees F (or higher) for a longer period of time.

Maintaining equipment

A pressure canner is safe to use as long as you maintain it according to the manufacturer’s directions. For example, every time you use it, you should check the vent and emergency release valve to make sure there are no blockages. Old pressure canners didn’t have safety release valves and occasionally exploded, which may be why some people are intimidated by them now.

Long term storage

Canning food can preserve it for up to five years. The Department of Agriculture says canned food is best eaten for taste within one year but can last up to three to five years. Store canned food in a cool, dry place. Before eating, check the contents of the jar for foul odors, leakage and discoloration. If you suspect the food has gone bad, don’t eat it (or even taste it).

Ronald Agrella is a freelance writer and former editor of The Boston Globe’s Boston.com.