It’s that time of the year when we drag trees, branches and even parasitic plants inside our homes. And by the time the new year rolls around we can be left looking at leafless poinsettias, crispy garlands and pine needles everywhere.

Where do these crazy traditions come from anyway?

There’s no definitive answer, but many scholars blame ... er, trace them back to ancient pagan beliefs that firs, pine and other evergreens symbolized eternal life, said Alain Touwaide, scientific director and founder of the Institute for the Preservation of Medical Traditions at the Huntington Library, which studies the historic use of plants.

Almost all populations celebrated the winter solstice (Dec. 21) as the turning point for the short, bleak days of winter. Bringing evergreen branches into the home was part of that hopeful tradition, “a symbol of winning over death and the continuity of nature,” Touwaide said.

Mistletoe, a poisonous, parasitic plant, was considered special by the Druids, particularly when it was found in oaks, he added. Mistletoe stayed green after the trees lost their leaves, and it became a symbol for fertility, which appears to have evolved to today’s tradition of hanging a sprig in a doorway and kissing any who pass underneath.

The Romans associated holly with the god Saturn, and they used it to make wreaths and decorative sprigs during Saturnalia on Dec. 17. The festival initially celebrated the end of one growing season and the start of another, Touwaide said, but eventually evolved into several days of revelry, gift giving and excessive drinking and eating. (Sound familiar?)

These days, all this holiday greenery doesn’t come cheap, so here are a few tips from Rex Yarwood, nursery manager at Roger’s Gardens in Corona del Mar, for keeping your investment looking good and avoiding any potential fire hazards:

Check for freshness

When shopping for holiday greenery, you can tell whether a wreath or garland is past its prime by grabbing the tip of a stem. “If it bends, it’s fresh,” Yarwood said. “If it breaks, it’s not.”

Hydrate, hydrate, hydrate

Give Christmas trees a good dunking before they come in the house. Ask the tree people to cut about half an inch off the trunk, then go directly home and let the tree soak in a bucket of water overnight. Hose it down to add extra moisture and remove any loose needles. Use a stand with a deep reservoir and keep replenishing the water once you bring the tree inside. Christmas tree preservatives are helpful too, Yarwood said; his favorite is called Keeps It Green.

Position wreaths and garlands in a tub or bucket so that their cut edges can soak in water overnight, then use a mister to add more moisture a few times a week. Yarwood says spray-on “freshness” products like Cloud Cover help preserve cut evergreens too.

Placement is important

Keep trees and garlands away from moisture-sucking heat sources and fire hazards, including fireplaces, candles or heating vents. If your front door gets full sun, keep your wreath inside until the last two weeks of the season. Otherwise, Yarwood said, “it’s going to be pretty darn crispy by Christmas.”

Remove those wrappers

Poinsettias and rosemary topiaries are common casualties, usually because of overwatering and lack of sunlight, Yarwood said. Keep them in a well-lighted room and remove their foil wrappers as soon as possible, or at least punch holes in the foil so the roots don’t drown in accumulated water. Soak the plants just once a week in the kitchen sink and let them drain before returning them to their perch. After the holidays you can replant them outside, in pots or the ground, in a sunny locale.

The most perishable