Michelle Obama unveils White House holiday decorations

• Gingerbread house weighs nearly 300 pounds
• First lady Michelle Obama welcomes military families
• More than 50 Christmas trees and a lot of references to dog Bo

It now has 54 Christmas trees, more than 80 seasonal volunteers representing all 50 states, and a gingerbread house that weighs nearly 300 pounds.

It's the White House during the holiday season.

First lady Michelle Obama unveiled the 2012 decorations in a special ceremony for selected military families and their children.

This year's theme is "Joy to All," Mrs. Obama said.

More than 90,000 visitors are expected to pass through the White House between now and the end of the year.

The biggest Christmas tree in the house -- an 18-foot-6-inch Fraser fir in the Blue Room on the ground floor -- features handmade decorations by children whose parents are stationed on military bases around the world.

Another tree features special Gold Star ornaments bearing the names of those who died in battle, making the ultimate sacrifice for their country.

Visitors can also fill out Operation Honor cards, which, Mrs. Obama said, "are used to pledge an individual service to their community in honor of our military families, servicemembers and veterans."

Praising her guests for their contributions, Mrs. Obama said, "our military families truly represent the very best that this country has to offer. ... This is one big, huge thank you."

Other trees feature ornamental tributes to past first ladies and their tributes to Christmas, going back to Jacqueline Kennedy's Nutcracker-themed decorations in the early 1960s.

A series of decorations throughout the house pay tribute to the family dog, Bo.

The first lady also highlighted the pride of the White House pastry kitchen, the gingerbread house that includes more than 175 pounds of gingerbread (and modified gingerbread) and more than 50 pounds of chocolate.

It is an exact replica of the White House -- complete with chandeliers that light up.

"It glows," Mrs. Obama noted, "like Rudolph's nose."

In front of the house: A very big gingerbread statue of Bo.

"That basically represents Bo's standing in the house," Mrs. Obama said. "He is such a big personality."

Among the highlights, as described by the White House:

• There are more than 40 "Bo-flake" ornaments throughout the White House.

• The snowflakes at the east entrance are made out of lightweight laminate board. Volunteers clipped and wired small boxwood bundles, dipped them in floor wax to preserve the freshness, and hot glued them to the frame. The project took approximately 25 volunteers a total of 100 hours to make.

•- The berry, pine cone and leaf designs on the east entrance column covers took a team of 40+ volunteers over two months to make. The column covers were constructed over a plywood base using 60,000 berries, 15,000 gold pine cone scales, and 15,000 pieces of lemon leaf. The pattern forms a three-dimensional geometric motif of "illusion cubes."

• The giant Bo topiary in Booksellers is made out of 18,000 one-inch black pom-poms and 2,000 white pom-poms. The pom-poms were strung on a single strand of yarn and then applied in an overlapping technique to resemble Bo's fur. The Bo topiary took one volunteer approximately 85 hours to complete.

• The colorful iron arches in the Lower Cross Hall are covered with over 6,000 re-purposed White House ornaments. The arches took a team of 12 volunteers a total of 350 hours to make.