Holly, with its glossy dark leaves and bright berries, continues to add visual interest to your landscape in the off season.

AP / Monrovia Nursery Co.

LOS ANGELES — For plant lovers, autumn’s arrival heralds the opening of a critical window of time in which they can prepare their gardens for the coming winter and set the stage for the spring bloom.

Ideally, one should begin winterizing their garden by November at the latest, or before prevailing temperatures hit the low 40s, experts say.

Whether it’s flowering plants adorning a home and backyard, or a vegetable garden, winterizing comes down to making changes to showcase plants that thrive in the winter, safeguard or remove those that don’t, and plant new bulbs for spring.

“When spring starts, plants wake up, they’ve come through the winter, they’ve had an extra drink, their roots have grown a little bit more in the wintertime and they’re absolutely ready to go,” said Nicholas Staddon, director of new plant introductions for Monrovia Nursery Co., a wholesale nursery operator based in Azuza, Calif.

“It’s really worth winterizing your garden properly.”

The first step, Staddon suggests, is for gardeners to ease back on fertilizing their gardens.

Fertilizers, particularly those with high levels of nitrogen, stimulate growth. But many plants, grass and trees tend to go into a dormant state in cold temperatures. In warm climates, using these fertilizers in winter months is OK.

One exception: fertilizers designed for winter use that target a plant’s root system rather than the above-ground parts, Staddon says.

To safeguard plants that could suffer root damage in low temperatures, experts recommend mulching and watering plants thoroughly.

Mulch is decomposed organic matter, which infuses soil with nutrients. Typically, plant lovers will mulch their garden once a year, but it’s important to do it before winter sets in so that plants’ root systems have something to feed on through the winter months. The mulch also protects plants from cold as the ground freezes. Apply no more than 2 inches, or pests and diseases can take hold.

Watering will be key, particularly in areas where there’s been a prolonged dry spell leading into winter. A deep soaking in the fall will ensure that plants will have some water in the ground to help them get through the dry, cold season to come.

For gardens in areas of the country with the harshest winters, some plants may need an extra layer of protection from the elements. Wrapping plants in straw, plastic or even specialty boxes made to shelter plants from cold may do the trick.

As for more fragile plants, or annuals that are not going to last into winter, it’s best to clear them out.

That’s an annual ritual for Althea Cawley-Murphree, who has been working on the plants and a vegetable garden around her home in Olympia, Wash., the past three years.

The 30-year-old publicist spends a good bit of time in the fall cutting back her shrubs, plants and grass. Most of her vegetables, including tomatoes, potatoes, peas, green beans and squash, don’t make it.

“So I just try to pull it all out, try to leave that soil with as few plants and as few leaves as possible,” she said.

Another strategy is to move plants into a planter and bring them inside the house or the garage.

Cawley-Murphree sometimes transplants geraniums into a planter and brings them inside her house, where they grow and flower all winter long.

“Geraniums are such a bright color, they have so many blossoms, it’s really nice to have that inside during the winter,” she said.

One bit of garden maintenance that experts say should be put off until winter is pruning trees. During spring, summer and fall, trees are in an active, growth phase, and pruning can stress them. In the winter, however, trees are, for the most part, dormant.

Also, in winter, trees often lose most of their leaves, making the task easier.

Experts say it’s best to cut branches that are rubbing against each other or those that are crisscrossing each other or growing back toward the trunk. That will help restore the natural shape of the tree.

Autumn is also a good time to design the look of the garden for winter and spring, which involves planting with an eye to having different plants peak through different seasons as others begin to die off.

Staddon calls it “event gardening.”

For a winter garden, select plants that have colorful branches or those hearty enough to retain their fruit and flowers.

“There are some beautiful things that survive in the snow,” said Tamra Stallings, who operates a Web site in which she shares how she goes about growing her own food in a large vegetable garden next to her home in Nashville, Tenn.

Some plants that stand out against a wintery backdrop: red-twig dogwood and oak-leaf hydrangea.

The dogwood sheds leaves in the fall and then its branches turn bright red. The oak leaf loses its leaves, too, then its white bark begins to peel back in layers.

Other good winter plants are hollies, witch hazel and ornamental grasses like those in the Miscanthus family.

What kind of plant will thrive in a given part of the country depends on how severe a winter they get. The U.S. Department of Agriculture hosts a map on its Web site that divides the country into temperature zones. From there, it’s easy to determine what some of the zone-appropriate plants are.

Autumn is also time to plant for spring, particularly trees and shrubs, because they need more time for their roots to settle into the ground.

On the Net:

USDA Plant Hardiness Zone Map: http://www.usna.usda.gov

/Hardzone/ushzmap.html